PK ;wEoa,mimetypeapplication/epub+zipPK;wEiTunesMetadata.plisty artistName Oracle Corporation book-info cover-image-hash 40603040 cover-image-path OEBPS/dcommon/oracle-logo.jpg package-file-hash 163476307 publisher-unique-id E13719-06 unique-id 36723375 genre Oracle Documentation itemName Oracle® Fusion Middleware Programming Enterprise JavaBeans for Oracle WebLogic Server, 11g Release 1 (10.3.6) releaseDate 2011-11-03T11:53:04Z year 2011 PKGm~yPK;wEMETA-INF/container.xml PKYuPK;wEOEBPS/ejbgen.htm EJBGen Reference

E EJBGen Reference

EJBGen is an Enterprise JavaBeans 2.x code generator. If you annotate your Bean class file with JDK 1.5 annotations, you can use EJBGen to generate the Remote and Home classes and the deployment descriptor files for an EJB application.

Oracle recommends that you use EJBGen to generate deployment descriptors; this Oracle best practice allows for easier and simpler maintenance of EJBs. If you use EJBGen, you need to write and annotate only one bean class file, which simplifies writing, debugging, and maintenance. The following sections provide instructions on using EJBGen and define EJBGen command options and annotations:

Running EJBGen

These sections describe how to process an annotated bean file using EJBGen:

EJBGen Distribution and Examples

In this release of WebLogic Server, EJBGen and associated classes are included in weblogic.jar in the WL_HOME/server/lib of the WebLogic Server distribution. To use EJBGen, make sure weblogic.jar is in your CLASSPATH. EJBGen annotations can be found in the weblogic.ejbgen package.

If you have installed Oracle WebLogic Server examples, see WL_HOME\samples\server\examples\src\examples\ejb\ejb20\ and WL_HOME\samples\server\examples\src\examples\ejb\ejb21\ for an application that uses EJBGen.

Invoking EJBGen

Use this command to run EJBGen on a bean source file:

com.bea.wls.ejbgen.EJBGen


Note:

To run this command, weblogic.jar must be in your CLASSPATH.

If you are invoking EJBGen for an EJB that has relationships with other EJBs, invoke the related EJBs by naming them, following your EJB, in the invocation, as follows:

com.bea.wls.ejbgen.EJBGen (YourBean).java (RelatedBean).java


Note:

You can also invoke EJBGen via the ejbgen ant task, which is also included in weblogic.jar.

EJBGen Command Options

Table E-1 defines EJBGen command options.

Table E-1 EJBGen Command Options

OptionDefaultDefinition

-checkTags

N/A

If invoked with this option, EJBGen will not generate any classes but will search the classes supplied on the command line for tags that are not valid EJBGen tags.

-classPath [directory]

N/A

Specifies the directory where the class loader can find dependent classes that are in .class format.

To specify more than one class path, separate paths with a semicolon (;).For instance: -classpath /dir1;/dir2

If dependent classes are in .java format, use -sourcePath instead.

-d [directory]

N/A

The directory under which all the files will be created.

-ddOnlyGen [boolean]

0

Tells the compiler to generate only the deployment descriptor files.

-descriptorDir [directory]

N/A

The directory under which all the descriptor files will be created, relative to the output directory specified with the -d [directory] option.

-docTag tagName

N/A

If specified, EJBGen prints out the detailed documentation for this tag, including all the recognized attributes. Note that even though this option does not need any source file, you still need to specify an existing .java class on the command line, or Javadoc will emit an error message even though it recognized the flag.

-docTags

N/A

Print out all the tags known by EJBGen. Note that even though this option does not need any source file, you still need to specify an existing .java class on the command line, or Javadoc will emit an error message even though it recognized the flag.

-docTagsHtml

N/A

Same as -docTags, but generates an HTML document.

-ejbPrefix [string]

" "

The prefix to use when generating the EJB class.

-ejbSuffix [string]

Bean or EJB

The suffix to use when generating the EJB class.

-ejbgenQuiet [boolean]

N/A

Make EJBGen less verbose.

-ejbgenVerbose [boolean]

N/A

Verbose mode.

-errorFile

N/A

The path of the file where errors will be redirected.

-exitOnError [boolean]

N/A

EJBGen should exit in case of an error.

-homeBaseClass [string (className)]

N/A

The base class for home remote interfaces.

-extractTemplates [directory]

N/A

The directory where to extract the templates.

-forceGeneration [boolean]

N/A

Force the generation of all files regardless of time stamps.

-homeBaseClass [string (className)]

N/A

The base class for home remote interfaces.

-ignorePackage

N/A

If this flag is set, EJBGen ignores the package name of the Java files it generates and creates those in the output directory as specified by the -d flag (or in the current directory if no -d was specified).

-jndiPrefix [string]

" "

The prefix to use for @remoteJndiName and @localJndiName.

-jndiSuffix [string]

" "

The suffix to use for @remoteJndiName and @localJndiName.

-localBaseClass [string (className)]

N/A

The base class for local interfaces.

-localHomeBaseClass [className]

N/A

The base class for local home interfaces.

-localHomePrefix [string]

" "

The prefix to use when generating the local EJB class.

-localHomeSuffix [string]

LocalHome

The suffix to use when generating the local EJB class.

-localPrefix [string]

" "

The prefix to use when generating the local EJB class.

-localSuffix [string] (

" "

The suffix to use when generating the local EJB class.

-noDDGen [boolean]

0

The compiler does not generate the deployment descriptor files.

-noImports [boolean]

false

Disable propagation of java imports to generated classes.

-noLocalInterfaces

N/A

If specified, local interfaces are not generated.

-noRedirection noRedirection ejbgen.noRedirection [boolean]

N/A

Cancels all redirection performed by EJBGen.

-noRemoteInterfaces [boolean]

N/A

If specified, remote interfaces are not generated.

-noticeFile [file]

N/A

The path of the file where notices will be redirected.

-noValueClasses [boolean]

N/A

If specified, value classes will not be generated.

-primaryKeyBaseClass [string (class name)]

N/A

The base class for generated primary keys.

-printDiagnostic [boolean]

N/A

Prints a diagnostic of all the tags found by EJBGen

-printTags [boolean]

N/A

Display all the tags recognized by EJBGen

-propertyFile [fileName]

N/A

The name of a property file that EJBGen reads to define substitution variables. See Using Property Files with EJBGen.

-remoteBaseClass [string (className)]

N/A

The base class for remote interfaces.

-remoteHomePrefix [string]

" "

The prefix to use when generating the remote EJB home class.

-remoteHomeSuffix [string]

" "

The suffix to use when generating the remote EJB home class.

-remotePrefix [string]

" "

The prefix to use when generating the remote EJB class.

-remoteSuffix [string]

" "

The suffix to use when generating the remote EJB class.

-source [version number]

1.5

Version of the JDK to use.

-sourcepath [directory]

N/A

Specifies the directory where the class loader can find dependent classes that are in .java format.

To specify more than one source path, separate paths with a semicolon (;).For instance: -sourcePath /dir1;/dir2

If dependent classes are in .class format, use -classPath instead.

-templateDir [directory]

N/A

The directory where the templates are stored.

-toStringForPrimitivesOnly

N/A

If specified, the toString() methods of value objects only display container-managed persistence fields that are primitives. This flag fixes the problem of circular references between value objects (AValue.toString() invoking BValue.toString() invoking AValue.toString(), etcetera).

-valueBaseClass [string (class name)]

N/A

The base class of the value class generated by EJBGen.

-valueObjectPrefix [string]

N/A

The prefix to use when generating the value object class.

-valueObjectSuffix [string]

N/A

The suffix to use when generating the value object class.

-valuePackage [string (package name)]

N/A

Package the value classes belong to.

-verbose [boolean]

false

Display more information.

-workshopDocTags [boolean]

N/A

Display the help in Oracle Workshop for WebLogic Platform HTML format.

-xmlEncoding [string]

N/A

The encoding to use when generating XML files (default: UTF-8).


Controlling the Files EJBGen Generates

By default, EJBGen generates the following files:

  • Remote bean and home interfaces (if weblogic.ejbgen.JndiName with "remote" was specified)

  • Local bean and home interfaces (if weblogic.ejbgen.JndiName with "local" was specified)

  • Value object classes

  • Primary key classes (if applicable)

You can selectively disable the generation of these files by using the weblogic.ejbgen.FileGeneration tag. This can be done on a per-bean basis.

Using Property Files with EJBGen

EJBGen can gather information for generation from property files, as discussed in this section.

Use the -propertyFile option to tell EJBGen to parse a properties file.

Use the following syntax to invoke EJBGen with the -propertyFile option:

com.bea.wls.ejbgen.EJBGen -propertyFile property-file AccountBean.java

EJBGen recognizes two kinds of variables in a properties file: user variables and predefined variables.

Using User Variables

EJBGen tags can use variables instead of strings. These variables must be enclosed with "${" and "}".

Variables can be used anywhere after an EJBGen tag, so they can contain whole tag definitions.

Using Predefined Variables

EJBGen recognizes a number of predefined variables. These variables are not supposed to be used in tags but EJBGen will use them at various places depending on their role. Recognized variables are:

  • remote.baseClass

    If specified, the value of this variable will be used as the base class for all generated remote classes.

  • home.baseClass

    If specified, the value of this variable will be used as the base class for all generated remote home classes.

  • local.baseClass

    If specified, the value of this variable will be used as the base class for all generated local classes.

  • localHome.baseClass

    If specified, the value of this variable will be used as the base class for all generated local home classes.

  • value.baseClass

    If specified, the value of this variable will be used as the base class for all generated value classes.

  • value.package

    If specified, the value of this variable will be used as the package for all generated value classes.

  • value.interfaces

    If specified, the value of this variable will be used as the interfaces the value class should implement. This variable can be a list of interfaces separated by commas.

You can make these variables more specific by prefixing them with an EJBName. For example, consider the following property file.

#
# property-file
#
Account.home.baseClass = BaseAccountHome
home.baseClass = BaseHome
value.package = value
containerManaged.value.package=valuePackageForContainerManaged

All homes generated by EJBGen extend the class BaseHome except the home of EJB "Account", which extends BaseAccountHome.

Surround Attributes that Contain Spaces With Double Quotes

When you specify an attribute that contains spaces, surround the attribute value with double quotes. For example:

group-names = "group1, group2"

EJBGen Supports Tag Inheritance

One of the main features in EJBGen 2.x is tag inheritance. You inherit EJBGen annotations the same way you do in Java. For example, assume that you have an EJB named AccountEJB with a base class BaseAccount, as in Example E-1:

weblogic.ejbgen.JndiName

Example E-1 Tag Inheritance

@JndiName(remote = "BaseRemote")

public class BaseAccount implements EntityBean {
// ...
}
Now, define your EJB class:
@Entity(ejbName = containerManaged,
    tableName = ejbAccounts,
    datasourceJndiName = examples-dataSource-demoPool)

//Note that we inherit the JNDI name defined in BaseAccount

public class AccountEJB extends BaseAccount {
// ...

Examples of EJBGen Tag Usage

These sections contain example source code annotated with EJBGen tags.

Mapping an Entity Bean to Several Tables with EJBGen

By default, entity beans are mapped to one table, with the attribute tableName on the tag @Entity. If you want to map your entity bean to more than one table, you can use the table-name attribute on individual @CmpFields provided the CMP fields are primary key fields that are mapped to corresponding primary key columns in each table. Any container-managed persistence fields that do not have a tableName attribute will use the table specified on @Entity (which can therefore be considered as the "default" table).

If you want to map an entity bean to several tables, you need to specify a comma-separated list of tables in the tableName attribute (and also on a column). Make sure that the number of tables matches the number of columns, and that the columns exist in the corresponding table.

Specifying Relationship Caching with EJBGen Tags

You can specify relationship caching elements with the @RelationshipCaching tag. This element can be nested (recursive). In other words, you can specify a tree representing all the relationship elements that you want to see cached.

In order to support this tree structure, @RelationshipCaching has two attributes, id and parentId. These attributes do not correspond to any XML, they simply allow you to specify your tree structure.

For example, if a cachingElement A needs to have two children elements B and C, all you need to specify is an id for A (say "root0") and a parentId for B and C equal to that name.

Example E-2 illustrates specifying relationship caching.

Example E-2 Specifying Relationship Caching

@RelationshipCachingElements(
@RelationshipCachingElement(cachingName = cacheMoreBeans,
 cmrField = employee,
 groupName = emp-group,
 id = A),
 
@RelationshipCachingElement(cachingName = cacheMoreBeans,
 cmrField = employee_ssn,
 groupName = emp-group,
 parentId = A),
 
@RelationshipCachingElement(cachingName = cacheMoreBeans,
 cmrField = employee_zip,
 groupName = emp-group,
    parentId = A)
)

Specifying Relationships with EJBGen Tags

Unidirectional relationships are achieved by specifying only the first two parameters of the relation tag (no CMR_field, no join table).


Note:

"Join table" was called "joint table" in pre-9.0 releases of WebLogic Server.

Many-to-many relationships must specify an extra table (parameter "join table") which must contain at least two columns. The names of these columns must match the names of the columns containing the foreign keys of the two beans being joined.

Upgrading Relationships to Use Local Interfaces

If you have EJBs based on a version of the EJB 2.0 specification that predates PFD2, you must update them. As of PFD2, relationships must be based on local interfaces, not remote ones. To upgrade your EJBs:

  1. Add a JNDI name for your local home interface:

    @JndiName
    remote = AccountHome
    local = AccountLocalHome
    
  2. Add @LocalMethod tags to any method you want to see appear on the local home interface. A method can have both @LocalMethod and @RemoteMethod.

  3. Change the return type of your container-managed relationship (CMP) accessing methods to that of the local EJB object (this only applies to single-valued CMR fields since multi-valued CMR fields are collections. Keep in mind that these collections contain Local EJB objects):

    @CmrField
    
    @RemoteMethod
    @LocalMethod
    
    abstract public LocalCustomer getCustomer();
    

Enum Attribute Constant Values

The following enum values are used for many of the EJBGen attributes.

Constants.Bool

Valid values for Constant.Bool are as follows:

  • Constants.Bool.UNSPECIFIED

  • Constants.Bool.TRUE

  • Constants.Bool.FALSE

Constants.TransactionAttribute

Valid values for Constants.TransactionAttribute are as follows:

  • Constants.TransactionAttribute.UNSPECIFIED

  • Constants.TransactionAttribute.NOT_SUPPORTED

  • Constants.TransactionAttribute.SUPPORTS

  • Constants.TransactionAttribute.REQUIRED

  • Constants.TransactionAttribute.REQUIRES_NEW

  • Constants.TransactionAttribute.MANDATORY

  • Constants.TransactionAttribute.NEVER

Constants.IsolationLevel

Valid values for Constants.IsolationLevel are as follows:

  • Constants.IsolationLevel.UNSPECIFIED

  • Constants.IsolationLevel.TRANSACTION_SERIALIZABLE

  • Constants.IsolationLevel.TRANSACTION_READ_COMMITTED

  • Constants.IsolationLevel.TRANSACTION_READ_UNCOMMITTED

  • Constants.IsolationLevel.TRANSACTION_REPEATABLE_READ

  • Constants.IsolationLevel.TRANSACTION_READ_COMMITTED_FOR_UPDATE

Constants.RefType

Valid values for Constant.RefType are as follows:

  • Constants.RefType.UNSPECIFIED

  • Constants.RefType.ENTITY

  • Constants.RefType.SESSION

Constants.HomeLoadAlgorithm

Valid values for Constants.HomeLoadAlgorithm are as follows:

  • Constants.HomeLoadAlgorithm.UNSPECIFIED

  • Constants.HomeLoadAlgorithm.ROUND_ROBIN

  • Constants.HomeLoadAlgorithm.RANDOM

  • Constants.HomeLoadAlgorithm.WEIGHT_BASED

  • Constants.HomeLoadAlgorithm.ROUND_ROBIN_AFFINITY

  • Constants.HomeLoadAlgorithm.RANDOM_AFFINITY

  • Constants.HomeLoadAlgorithm.WEIGHT_BASED_AFFINITY

Constants.Interface

Valid values for Contants.Interface are as follows:

  • Constants.Interface.UNSPECIFIED

  • Constants.Interface.HOME

  • Constants.Interface.REMOTE

  • Constants.Interface.LOCAL_HOME

  • Constants.Interface.LOCAL

Constants.ConcurrencyStrategy

Valid values for Constants.ConcurrencyStrategy are as follows:

  • Constants.ConcurrencyStrategy.UNSPECIFIED

  • Constants.ConcurrencyStrategy.READ_ONLY

  • Constants.ConcurrencyStrategy.EXCLUSIVE

  • Constants.ConcurrencyStrategy.DATABASE

  • Constants.ConcurrencyStrategy.OPTIMISTIC

EJBGen Annotation Reference

This section provides a complete reference for the following EJBGen annotations you can use in your bean class file:

EJB Container Annotations

The following is a list of container annotations that can only contain an array of annotations.


Note:

A single class or method can be annotated by no more than one instance of any annotation.

For more information on an annotation, including the array of annotations it can contain, click the annotation name.

weblogic.ejbgen.ActivationConfigProperties

Target: Class

This annotation does not have any attributes, other than the array of weblogic.ejbgen.ActivationConfigProperty annotations.

weblogic.ejbgen.ActivationConfigProperty

Target: Class

Attributes

Table E-2 ActivationConfigProperty EJBGen Annotation Attributes

NameDescriptionData TypeRequired?

value

Property Value.

String

Yes

name

Property name.

String

Yes


weblogic.ejbgen.AutomaticKeyGeneration

Target: Class

Attributes

Table E-3 AutomaticKeyGeneration EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

type

The type of the key generator.

Valid values for this attribute are:

  • AutomaticKeyGeneration.AutomaticKeyGenerationType.UNSPECIFIED

  • AutomaticKeyGeneration.AutomaticKeyGenerationType.IDENTITY

  • AutomaticKeyGeneration.AutomaticKeyGenerationType.SEQUENCE

  • AutomaticKeyGeneration.AutomaticKeyGenerationType.SEQUENCE_TABLE

Enum

Yes

cacheSize

The size of the key cache. The default value of this attribute is UNSPECIFIED.

String

No (Previously yes)

name

The name of the generator. The default value of this attribute is UNSPECIFIED.

String

No


weblogic.ejbgen.CmpField

Target: Method

Attributes

Table E-4 CmpField EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

column

The column where this CMP field will be mapped. See Mapping an Entity Bean to Several Tables with EJBGen.

String

Yes

readOnlyInValueObject

If True, only the getter will be generated for this field in the value object.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

tableName

The table(s) where this field should be mapped.

See Mapping an Entity Bean to Several Tables with EJBGen. The default value for this attribute is UNSPECIFIED.

String.

No

groupNames

Comma-delimited names of the groups this field belongs to. Surround the list of group names with double quotes. The default value for this attribute is UNSPECIFIED.

String

No

orderingNumber

The number where this field must appear in signatures and constructors. For this ordering to work, all cmr and cmp fields must set this attribute to a distinct numeric value.The default value for this attribute is 0.

String

No

excludeFromValueObject

If True, this field will not be generated in the value object.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

columnType

The type of this column.Valid values for this attribute are:

  • CmpField.ColumnType.UNSPECIFIED

  • CmpField.ColumnType.CLOB

  • CmpField.ColumnType.BLOB

  • CmpField.ColumnType.LONG_STRING

  • CmpField.ColumnType.SYBASE_BINARY

The default value is CmpField.ColumnType.UNSPECIFIED.

Enum

No

primkeyField

Whether this field is part of the compound primary key.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

dbmsDefaultValue

Whether this field is the default DBMS value.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No


weblogic.ejbgen.CmrField

Target: Method

Attributes

Table E-5 CmrField EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

readOnlyInValueObject

If True, only the getter will be generated for this field in the value object.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

groupNames

Comma-delimited names of the groups this field belongs to. Surround the list of group names with double quotes.

The default value for this attribute is UNSPECIFIED.

String

No

orderingNumber

The number where this field must appear in signatures and constructors. For this ordering to work, all cmr and cmp fields must have this attribute to a distinct numeric value. The default value for this attribute is UNSPECIFIED.

String

No

excludeFromValueObject

If True, this field will not be generated in the value object.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No


weblogic.ejbgen.Compatibility

Target: Class

Attributes

Table E-6 Compatibility EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

serializeCharArrayToBytes

Whether a cmp-field of type byte[] mapped to a Blob in an Oracle database should be serialized.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

disableStringTrimming

Whether to disable String trimming.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

serializeByteArrayToOracleBlob

Whether a cmp-field of type byte[] mapped to an OracleBlob should be serialized.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

allowReadonlyCreateAndRemove

Whether to allow read only create and remove.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

findersReturnNulls

Whether to allow finder methods to return null.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No


weblogic.ejbgen.CreateDefaultDbmsTables

This tag is deprecated; use weblogic.ejbgen.JarSettings instead.

weblogic.ejbgen.CreateDefaultRdbmsTables

This tag is deprecated; use weblogic.ejbgen.JarSettings instead.

weblogic.ejbgen.DBSpecificSQL

Target: Class, Method, Field

Attributes

Table E-7 DBSpecificSQL EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

databaseType

The database type.

String

Yes

sql

The SQL statement.

String.

Yes


weblogic.ejbgen.EjbClientJar

This tag is deprecated; use weblogic.ejbgen.JarSettings instead.

weblogic.ejbgen.EjbInterface (deprecated)


Note:

This class has been deprecated and will be removed in a future release.

Target: Class

Attributes

Table E-8 EjbInterface EJBGen Annotation Attributes

AttributesDescriptionData TypeRequired?

ejbType

Specifies the type of this EJB. This tag is not normally used.

Valid values are:

  • javax.ejb.MessageDrivenBean

  • javax.ejb.EntityBean

  • javax.ejb.SessionBean

String

Yes


weblogic.ejbgen.EjbLocalRef

Target: Class

Attributes

Table E-9 EjbLocalRef EJBGen Annotation Attributes

AttributesDescriptionData TypeRequired?

jndiName

Specifies the JNDI name of the reference.

The default value of this attribute is UNSPECIFIED.

String

No

type

Specifies the reference type.

See Constants.RefType for the list of valid values for this attribute. The default value is Constants.RefType.UNSPECIFIED.

Enum (Constants.RefType)

No

local

Names the Local class of the bean. The default value of this attribute is UNSPECIFIED.

String

No

name

Names the reference. The default value of this attribute is UNSPECIFIED.

String

No

link

Names the link of the bean. The default value of this attribute is UNSPECIFIED.

String

No

id

The identity of this tag (used for tag inheritance only). The default value of this attribute is UNSPECIFIED.

String

No

home

Names the Home class of this bean. The default value of this attribute is UNSPECIFIED.

String

No


weblogic.ejbgen.EjbLocalRefs

Target: Class

This annotation does not have any attributes, other than the array of weblogic.ejbgen.EjbLocalRefs annotations.

weblogic.ejbgen.EjbRef

Target: Class

Attributes

Table E-10 EjbRef EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

jndiName

Specifies the JNDI name of the reference. The default value of this attribute is UNSPECIFIED.

String

No

type

Specifies the reference type.

See Constants.RefType for the list of valid values for this attribute. The default value is Constants.RefType.UNSPECIFIED.

Enum (Constants.RefType)

No

remote

Names the Local class of the bean. The default value of this attribute is UNSPECIFIED.

String

No

name

Names the reference. The default value of this attribute is UNSPECIFIED.

String

No

link

Names the link of the bean. The default value of this attribute is UNSPECIFIED.

String

No

id

The identity of this tag (used for tag inheritance only). The default value of this attribute is UNSPECIFIED.

String

No

home

Names the Home class of this bean. The default value of this attribute is UNSPECIFIED.

String

No


weblogic.ejbgen.EjbRefs

Target: Class

This annotation does not have any attributes, other than the array of weblogic.ejbgen.EjbRef annotations.

weblogic.ejbgen.Entity

Target: Class

Attributes

Table E-11 Entity EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

ejbName

The name of this entity bean.

String

Yes

primKeyClass

Names the Java class of the primary key. In case of a compound primary key, this class will be generated by EJBGen.

String

Yes

tableName

Names the table to which this entity bean is mapped. The default value of this attribute is UNSPECIFIED.

String

No

verifyRows

Specifies the rows in a table that should be checked when optimistic concurrency is used.

The valid values for this attribute are:

  • Entity.VerifyRows.UNSPECIFIED

  • Entity.VerifyRows.READ

  • Entity.VerifyRows.MODIFIED

The default value is Entity.VerifyRows.UNSPECIFIED.

Enum

No

clientsOnSameServer

Specifies whether the clients are collocated with the EJB on the same server.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

invalidationTarget

Targets the ejb-name of a read-only entity bean to be invalidated when this container-managed persistence entity EJB is modified. The default value of this attribute is UNSPECIFIED.

String

No

useCallerIdentity

Determines whether or not this EJB uses the caller's identity.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

cacheBetweenTransactions

Specifies whether to cache the persistent data of an entity bean across (between) transactions.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

defaultDbmsTablesDdl

Defines the DDL filename. The default value for this attribute is UNSPECIFIED.

String

No

defaultTransaction

Sets the default transaction attribute to be applied to all methods that do not have a transaction attribute setting.

See Constants.TransactionAttribute for valid values for this attribute. The default value is Constants.TransactionAttribute.UNSPECIFIED.

Enum (Constants.TransactionAttribute)

No

checkExistsOnMethod

Specifies whether the container checks for the existence of a bean for each method call.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

clusterInvalidationDisabled

For an EJB that uses Optimistic or ReadOnly concurrency, specifies whether the EJB is invalidated when it is updated by a member of a cluster to which it is deployed. When true, the container does not send out multicast invalidation messages when such EJBs are updated.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

optimisticColumn

Specifies the column that holds the timestamp for optimistic concurrency. The default value for this attribute is UNSPECIFIED.

String

No

orderDatabaseOperations

Determines whether to sort the database operations.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

runAsIdentityPrincipal

Deprecated. Use runAsPrincipalName instead.

String

No

runAsPrincipalName

Gives the name of the principal in case the role maps to several principals. The default value for this attribute is UNSPECIFIED.

String

No

delayDatabaseInsertUntil

Specifies until when database inserts should be delayed.

Valid values for this attribute are as follows:

  • Entity.DelayDatabaseInsertUntil.UNSPECIFIED

  • Entity.DelayDatabaseInsertUntil.EJB_CREATE

  • Entity.DelayDatabaseInsertUntil.EJB_POST_CREATE

The default value is Entity.DelayDatabaseInsertUntil.UNSPECIFIED.

Enum

No

enableCallByReference

Specifies whether the container will call this EJB by reference.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

validateDbSchemaWith

Specifies the method used to validate the tables created by the EJB container.

Valid values for this attribute are as follows:

  • Entity.ValidateDBSchemaWith.UNSPECIFIED

  • Entity.ValidateDBSchemaWith.META_DATA

  • Entity.ValidateDBSchemaWith.TABLE_QUERY

The default value is Entity.ValidateDBSchemaWith.UNSPECIFIED.

Enum

No

dispatchPolicy

Specifies the dispatch policy queue for this bean. The default value for this attribute is UNSPECIFIED.

String

No

remoteClientTimeout

Specifies the length of time that a remote RMI client will wait before it will time out. The default value of this attribute is UNSPECIFIED

String

No

lockOrder

Sets the database locking order of this bean when a transaction involves multiple beans. The default value of this attribute is UNSPECIFIED.

String

No

findersLoadBean

If set to True, the beans will immediately be loaded into the cache by the finder.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

concurrencyStrategy

Defines the concurrency strategy for this bean.

See Constants.ConcurrencyStrategy for the list of valid values for this attribute. The default value is Constants.ConcurrencyStrategy.UNSPECIFIED.

Enum (Constants.ConcurrencyStrategy)

No

persistenceType

Sets the type of this Entity bean.

Valid values for this attribute are as follows:

  • Entity.PersistenceType.UNSPECIFIED

  • Entity.PersistenceType.CMP

  • Entity.PersistenceType.BMP

The default value is Entity.PersistenceType.UNSPECIFIED.

Enum

No

maxBeansInCache

Sets the maximum number of beans in the cache. The default value of this attribute is UNSPECIFIED.

String

No

primKeyClassNogen

If this keyword is specified, EJBGen will not generate the primary key class (it is assumed that you are providing it).

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

initialBeansInFreePool

Specifies the initial number of beans in the free pool.

Default value of this attribute is UNSPECIFIED.

String

No

verifyColumns

Specifies how optimistic concurrency verifies that the columns have or have not been modified during transactions.

The valid values for this attribute are:

  • Entity.VerifyColumns.UNSPECIFIED

  • Entity.VerifyColumns.READ

  • Entity.VerifyColumns.MODIFIED

  • Entity.VerifyColumns.VERSION

  • Entity.VerifyColumns.TIMESTAMP

The default value is Entity.VerifyColumns.UNSPECIFIED.

Enum

No

idleTimeoutSeconds

Sets the maximum duration an EJB should stay in the cache, in seconds. The default value of this attribute is UNSPECIFIED.

String

No

transTimeoutSeconds

Sets the transaction timeout (in seconds). The default value of this attribute is UNSPECIFIED.

String

No

enableBatchOperations

Determines whether to perform batch operations.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

maxBeansInFreePool

Specifies the maximum number of beans in the free pool. The default value of this attribute is UNSPECIFIED.

String

No

disableWarning

A comma-separated line of warnings to disable when running ejbc. The default value of this attribute is UNSPECIFIED.

String

No

readTimeoutSeconds

Sets the number of seconds between each ejbLoad() call on a read-only Entity bean. The default value of this attribute is UNSPECIFIED.

String

No

databaseType

Specifies the database type of the underlying DBMS.

Valid values for this attribute are:

  • Entity.DatabaseType.UNSPECIFIED

  • Entity.DatabaseType.DB2

  • Entity.DatabaseType.INFORMIX

  • Entity.DatabaseType.ORACLE

  • Entity.DatabaseType.SQL_SERVER

  • Entity.DatabaseType.SYBASE

  • Entity.DatabaseType.SQL_SERVER200

The default value is Entity.DatabaseType.UNSPECIFIED.

Enum

No

reentrant

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

homeLoadAlgorithm

Specifies the algorithm to use for load-balancing between replicas of this home.

See Constants.HomeLoadAlgorithm for the list of valid values for this attribute.

The default value is Constants.HomeLoadAlgorithm.UNSPECIFIED.

Enum (Constants.HomeLoadAlgorithm)

No

delayUpdatesUntilEndOfTx

Determines whether updates will be sent after the transaction has been committed.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

runAs

Specifies the role-name for this EJB. The default value of this attribute is UNSPECIFIED.

String

No

abstractSchemaName

Gives the abstract schema name for this EJB. If not specified, the ejb-name value will be used. The default value of this attribute is UNSPECIFIED.

String

No

dbIsShared

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

enableDynamicQueries

Specifies whether dynamic queries are enabled.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

homeIsClusterable

Determines whether this bean can be deployed from multiple servers in a cluster.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

dataSourceName

Names the data source declared in config.xml. The default value of this attribute is UNSPECIFIED.

String

No

useSelectForUpdate

If true, causes SELECT ... FOR UPDATE to be used whenever the bean is loaded from the database.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

instanceLockOrder

The locking order for this Entity bean.

  • Valid values for this attribute are:

  • Entity.InstanceLockOrder.UNSPECIFIED

  • Entity.InstanceLockOrder.ACCESS_ORDER

  • Entity.InstanceLockOrder.VALUE_ORDER

The default value is Entity.InstanceLockOrder.UNSPECIFIED.

Enum

No

homeCallRouterClassName

Names the class to be used for routing home method calls. The default value of this attribute is UNSPECIFIED.

String

No

networkAccessPoint

Assigns a custom network channel that the EJB will use for network communications. A network channel defines a set of connection attributes The default value of this attribute is UNSPECIFIED.

String

No

unknownPrimaryKeyField

The cmp fields to use as the primary key when the primary key is not specified. The default value of this attribute is UNSPECIFIED.

String

No


weblogic.ejbgen.EntityCacheRef

Target: Class

Attributes

Table E-12 EntityCacheRef EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

concurrencyStrategy

Defines the concurrency strategy for this bean.

See Constants.ConcurrencyStrategy for valid values for this attribute.

Enum ( Constants.ConcurrencyStrategy)

Yes

name

Names the cache.

String

Yes

idleTimeoutSeconds

Maximum duration an EJB should stay in the cache. The default value for this attribute is 0.

int

No

readTimeoutSeconds

The number of seconds between each ejbLoad() call on a read-only entity bean. The default value for this attribute is 0.

int

No

cacheBetweenTransactions

Indicates whether to cache the persistent data of an entity bean across (between) transactions.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

estimatedBeanSize

The estimated average size of the instances of an entity bean, in bytes. The default value for this attribute is UNSPECIFIED.

String

No


weblogic.ejbgen.EnvEntries

Target: Class

This annotation does not have any attributes, other than the array of weblogic.ejbgen.EnvEntry annotations.

weblogic.ejbgen.EnvEntry

Target: Class

Attributes

Table E-13 EnvEntry EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

value

Specifies the value for this environment entry.

String

Yes

type

Specifies the Java type for this environment entry (must be fully qualified, even if the type is java.lang).

Standard valid values include:

  • java.lang.Boolean

  • java.lang.String

  • java.lang.Character

  • java.lang.Integer

  • java.lang.Double

  • java.lang.Byte

  • java.lang.Short

  • java.lang.Long

  • java.lang.Float

String

Yes

name

Names this environment entry.

String

Yes


weblogic.ejbgen.FileGeneration

Target: Class

Attributes

Table E-14 FileGeneration EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

pkClass

Whether to generate the primary key class for this EJB.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.TRUE.

Enum (Constants.Bool)

No

remoteClassName

The name of the remote class to be generated.

The default value for this attribute is UNSPECIFIED.

String

No

remotePackage

The package for the remote interface.

The default value for this attribute is UNSPECIFIED.

String

No

valueClass

Specifies whether to generate the value class for this EJB.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

valueClassName

The name of the value class to be generated.

The default value for this attribute is UNSPECIFIED.

String

No

localClassName

The name of the local class to be generated.

The default value of this attribute is UNSPECIFIED.

String

No

localPackage

The package for the local interface.

The default value for this attribute is UNSPECIFIED.

String

No

remoteHome

Specifies whether to generate the remote home interface for this EJB.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

localHomePackage

The package for the local home interface.

The default value for this attribute is UNSPECIFIED.

String

No

remoteHomePackage

The package for the remote home interface.

The default value for this attribute is UNSPECIFIED.

String

No

remoteClass

Specifies whether to generate the remote interface for this EJB.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

localHomeName

The name of the local home class to be generated.

The default value for this attribute is UNSPECIFIED.

String

No

localHome

Whether to generate the local home interface for this EJB.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

remoteHomeName

The name of the remote home class to be generated.

The default value for this attribute is UNSPECIFIED.

String

No

localClass

Whether to generate the local interface for this EJB.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No


weblogic.ejbgen.Finder

Target: Class

Attributes

Table E-15 Finder EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

isolationLevel

Specifies the type of transaction isolation for this method.

See Constants.IsolationLevel for valid values for this attribute.

The default value is Constants.IsolationLevel.UNSPECIFIED.

Enum (Constants.IsolationLevel)

No

transactionAttribute

Specifies the transaction attribute for this local method. If not specified, the default transaction attribute will be used. Methods with this tag will be generated on the Local class.

See Constants.TransactionAttribute for valid values for this attribute. The default value is Constants.TransactionAttribute.UNSPECIFIED.

Enum (Constants.TransactionAttribute)

No

generateOn

Determines which Home this finder will be generated on. If the value of this attribute is unspecified, the finder will be generated on both the Remote and Local Home.

Valid values for this attribute are as follows:

  • Finder.GenerateOn.UNSPECIFIED

  • Finder.GenerateOn.LOCAL

  • Finder.GenerateOn.REMOTE

The default value is Finder.GenerateOn.UNSPECIFIED.

Enum

No

comment

Defines a comment that will be reproduced above the generated finder Java method. The default value for this attribute is UNSPECIFIED.

String

No

id

The identity of this tag (used for tag inheritance only). The default value for this attribute is UNSPECIFIED.

String

No

cachingName

Specifies the name of an eager relationship caching. The default value for this attribute is UNSPECIFIED.

String

No

groupName

Names the group for the WebLogic Server query. The default value for this attribute is UNSPECIFIED.

String

No

maxElements

Specifies the maximum number of elements that should be returned by a multi-valued query. The default value for this attribute is UNSPECIFIED.

String

No

signature

Specifies exactly the signature to be generated on the Home class. EJBGen will add the conformant exceptions, but you must specify the fully-qualified type of each parameter, even if it belongs to java.lang. The default value for this attribute is UNSPECIFIED.

String

No

sqlSelectDistinct

Determines whether the generated SQL SELECT will contain a DISTINCT qualifier.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

includeUpdates

Determines whether updates made during the current transaction must be reflected in the result of a query.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

ejbQL

Specifies the EJB QL request as it will appear in the deployment descriptor. The default value for this attribute is UNSPECIFIED.

String

No

weblogicEjbQl

Specifies the Weblogic Server EJB QL request as it will appear in the deployment descriptor.

Note: If this request is needed, enclose both EJB-QL and Weblogic Server EJB-QL within double quotes. The default value for this attribute is UNSPECIFIED.

String

No


weblogic.ejbgen.Finders

Target: Class

This annotation does not have any attributes, other than the array of weblogic.ejbgen.Finder annotations.

weblogic.ejbgen.ForeignJmsProvider

Target: Class

Attributes

Table E-16 ForeignJmsProvider EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

connectionFactoryJndiName

Specifies the connection factory JNDI name. The default value for this attribute is UNSPECIFIED.

String

No

providerUrl

Specifies the provider URL. The default value for this attribute is UNSPECIFIED.

String

No

initialContextFactory

Specifies the initial JNDI context factory. The default value for this attribute is UNSPECIFIED.

String

No


weblogic.ejbgen.JarSettings

Target: Class

Attributes

Table E-17 JarSettings EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

createTables

Specifies whether to create tables.

Valid values for this attribute are:

  • JarSettings.CreateTables.UNSPECIFIED

  • JarSettings.CreateTables.CREATE_ONLY

  • JarSettings.CreateTables.DISABLED

  • JarSettings.CreateTables.DROP_AND_CREATE

  • JarSettings.CreateTables.DROP_AND_CREATE_ALWAYS

  • JarSettings.CreateTables.ALTER_OR_CREATE

The default value is arSettings.CreateTables.UNSPECIFIED.

Enum

No

ejbClientJar

Specifies the name of the client JAR to be generated. If multiple EJBs have this tag, only one of the specified JAR files will be included in the deployment descriptor. The default value of this attribute is UNSPECIFIED.

String

No

enableBeanClassRedeploy

Determines whether this EJB can be redeployed without redeploying the entire module.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

disableWarning

A comma-separated line of warnings to disable when running ejbc. The default value of this attribute is UNSPECIFIED.

String

No


weblogic.ejbgen.JndiName

Target: Class

Attributes

Table E-18 JndiName EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

local

Specifies the local JNDI name of this EJB. If a local JNDI name is not specified, no local interfaces will be generated. The default value of this attribute is UNSPECIFIED.

String

No

remote

Specifies the remote JNDI name of this EJB. If a remote JNDI name is not specified, no remote interfaces will be generated. The default value of this attribute is UNSPECIFIED.

String

No


weblogic.ejbgen.LocalHomeMethod

Target: Method

Attributes

Table E-19 LocalHomeMethod EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

orderingNumber

Specifies the number where this method must appear in the generated class. The default value of this attribute is UNSPECIFIED.

String

No

isolationLevel

Specifies the type of transaction isolation for this method.

See Constants.IsolationLevel for valid values for this attribute. The default value is Constants.IsolationLevel.UNSPECIFIED.

Enum (Constants.IsolationLevel)

No

transactionAttribute

Specifies the transaction attribute for this local method. If not specified, the default transaction attribute will be used. Methods with this tag will be generated on the Local class.

See Constants.TransactionAttribute for valid values for this attribute. The default value is Constants.TransactionAttribute.UNSPECIFIED.

Enum (Constants.TransactionAttribute)

No

roles

Defines a comma-separated list of roles that are allowed to invoke this method. The default value of this attribute is UNSPECIFIED.

String

No

isIdempotent

Sets whether this method is idempotent.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

retryCount

The number of retries for this method on a rollback. The default value of this attribute is 0.

int

No


weblogic.ejbgen.LocalMethod

Target: Method

Attributes

Table E-20 LocalMethod EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

orderingNumber

Specifies the number where this method must appear in the generated class.

The default value of this attribute is UNSPECIFIED.

String

No

isolationLevel

Specifies the type of transaction isolation for this method.

See Constants.IsolationLevel for valid values for this attribute. The default value is Constants.IsolationLevel.UNSPECIFIED.

Enum (Constants.IsolationLevel)

No

transactionAttribute

Specifies the transaction attribute for this local method. If not specified, the default transaction attribute will be used. Methods with this tag will be generated on the Local class.

See Constants.TransactionAttribute for valid values for this attribute. The default value is Constants.TransactionAttribute.UNSPECIFIED.

Enum (Constants.TransactionAttribute)

No

roles

Defines a comma-separated list of roles that are allowed to invoke this method. The default value of this attribute is UNSPECIFIED.

String

No

isIdempotent

Sets whether this method is idempotent.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

retryCount

The number of retries for this method on a rollback. The default value of this attribute is 0.

int

No


weblogic.ejbgen.MessageDestination

Target: Class

Attributes

Table E-21 MessageDestination EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

name

Logical name of the message destination.

String

Yes

destinationJndiName

The JNDI name of the physical message destination. The default value of this attribute is UNSPECIFIED.

String

No

providerUrl

The URL of the provider. The default value of this attribute is UNSPECIFIED.

String

No

initialContextFactory

The initial context factory. The default value of this attribute is UNSPECIFIED.

String

No


weblogic.ejbgen.MessageDestinationRef

Target: Class

Attributes

Table E-22 MessageDestinationRef EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

messageDestinationType

The reference type.

String

Yes

messageDestinationLink

Link to the message destination.

String

Yes

name

Name of the reference.

String

Yes

messageDestinationUsage

Usage of the reference.

String

Yes


weblogic.ejbgen.MessageDestinationRefs

Target: Class

This annotation does not have any attributes, other than the array of weblogic.ejbgen.MessageDestinationRef annotations.

weblogic.ejbgen.MessageDestinations

Target: Class

This annotation does not have any attributes, other than the array of weblogic.ejbgen.MessageDestination annotations.

weblogic.ejbgen.MessageDriven

Target: Class

Attributes

Table E-23 MessageDriven EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

ejbName

Specifies the name of this Message-Driven bean.

String

Yes

destinationJndiName

Gives the JNDI name of the destination of this message-driven bean. The default value of this attribute is UNSPECIFIED.

String

No

destinationType

Valid values are javax.jms.Queue and javax.jms.Topic. The default value of this attribute is UNSPECIFIED.

String

Yes

messageSelector

The JMS message selector. The default value of this attribute is UNSPECIFIED.

String

No

durable

If the destinationType is Topic, setting this attribute to True will make the subscription durable.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

initialBeansInFreePool

Specifies the initial number of beans in the free pool. The default value of this attribute is UNSPECIFIED.

String

No

clientsOnSameServer

Specifies whether the clients are collocated with the EJB on the same server.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

jmsPollingIntervalSeconds

The number of seconds between each attempt to reconnect to the JMS destination. The default value of this attribute is UNSPECIFIED.

String

No

removeAsPrincipalName

Names the principal to be used when ejbRemove would otherwise run with an anonymous principal. The default value of this attribute is UNSPECIFIED.

String

No

transactionType

Specifies where the transactions for this EJB are managed.

Valid values for this attribute are:

  • MessageDriven.MessageDrivenTransactionType.UNSPECIFIED

  • MessageDriven.MessageDrivenTransactionType.BEAN

  • MessageDriven.MessageDrivenTransactionType.CONTAINER

The default value is MessageDriven.MessageDrivenTransactionType.UNSPECIFIED.

Enum

No

transTimeoutSeconds

Specifies the transaction timeout (in seconds). The default value of this attribute is UNSPECIFIED.

String

No

useCallerIdentity

Specifies whether this EJB uses callers identity.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

maxBeansInFreePool

Specifies the maximum number of beans in the free pool. The default value of this attribute is UNSPECIFIED.

String

No

defaultTransaction

Specifies the transaction attribute to be applied to all methods that do not have a specific transaction attribute setting.

Valid values for this attribute are:

  • MessageDriven.DefaultTransaction.UNSPECIFIED

  • MessageDriven.DefaultTransaction.NOT_SUPPORTED

  • MessageDriven.DefaultTransaction.REQUIRED

The default value is MessageDriven.DefaultTransaction.UNSPECIFIED.

Enum

No

runAsIdentityPrincipal

Deprecated. Use runAsPrincipalName instead.

String

No

runAsPrincipalName

Gives the name of the principal in case the role maps to several principals. The default value for this attribute is UNSPECIFIED.

String

No

dispatchPolicy

Specifies the dispatch policy queue for this bean. The default value of this attribute is UNSPECIFIED.

String

No

remoteClientTimeout

Specifies the length of time that a remote RMI client will wait before it will time out. The default value of this attribute is UNSPECIFIED

String

No

passivateAsPrincipalName

Names the principal to be used when ejbPassivate would otherwise run with an anonymous principal.

The default value of this attribute is UNSPECIFIED.

String

No

acknowledgeMode

Specifies the acknowledgement mode of this message-driven bean.

Valid values for this attribute are:

  • MessageDriven.AcknowledgeMode.UNSPECIFIED

  • MessageDriven.AcknowledgeMode.AUTO_ACKNOWLEDGE

  • MessageDriven.AcknowledgeMode.DUPS_OK_ACKNOWLEDGE

The default value is MessageDriven.AcknowledgeMode.UNSPECIFIED.

Enum

No

runAs

Specifies the role-name for this EJB. The default value of this attribute is UNSPECIFIED.

String

No

jmsClientId

The client ID of this EJB. The default value of this attribute is UNSPECIFIED.

String

No

createAsPrincipalName

Names the principal to be used when ejbCreate would otherwise run with an anonymous principal. The default value of this attribute is UNSPECIFIED.

String

No

networkAccessPoint

Assigns a custom network channel that the EJB will use for network communications. A network channel defines a set of connection attributes. The default value of this attribute is UNSPECIFIED.

String

No

messagingType

The default value of this attribute is UNSPECIFIED.

String

No

initSuspendSeconds

The initial number of seconds to suspend an MDB's JMS connection when the EJB container detects a JMS resource outage. The default value of this attribute is 0.

int

No

maxSuspendSeconds

Specifies the maximum number of seconds to suspend an MDB's JMS connection when the EJB container detects a JMS resource outage. The default value of this attribute is 0.

int

No

generateUniqueJmsClientId

Indicates whether or not you want the EJB container to generate a unique client-id for every instance of an MDB which makes is easier to deploy durable MDBs to multiple server instances in a WebLogic Server cluster.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

durableSubscriptionDeletion

Specifies whether you want durable topic subscriptions to be automatically deleted when an MDB is undeployed or removed.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

maxMessagesInTransaction

The maximum number of messages in the transaction. The default value of this attribute is 0.

int

No

resourceAdapterJndiName

The resource adapter JNDI name. The default value of this attribute is UNSPECIFIED.

String

No


weblogic.ejbgen.MethodIsolationLevelPattern

Target: Class

Attributes

Table E-24 MethodIsolationLevelPattern EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

isolationLevel

Specifies the isolation level for the methods specified in the pattern tag.

See Constants.IsolationLevel for valid values for this attribute.

Enum (Constants.IsolationLevel)

Yes

pattern

Specifies the pattern that matches all methods that will receive this isolation level (e.g. "*").

String

Yes

id

The identity of this tag (used for tag inheritance only). The default value for this attribute is UNSPECIFIED.

String

No


weblogic.ejbgen.MethodIsolationLevelPatterns

Target: Class

This annotation does not have any attributes, other than the array of weblogic.ejbgen.MethodIsolationLevelPattern annotations.

weblogic.ejbgen.MethodPermissionPattern

Target: Class

Attributes

Table E-25 MethodPermissionPattern EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

pattern

Specifies the pattern that matches all methods that will receive this method permission (e.g. "*").

String

Yes

roles

Specifies the roles for the methods specified in the pattern tag, separated by a comma.

String

Yes

itf

Specifies the interface to which this permission pattern applies.

See Constants.Interface for valid values for this attribute.

The default value is Constants.Interface.UNSPECIFIED.

Enum (Constants.Interface)

No

id

The identity of this tag (used for tag inheritance only). The default value for this attribute is UNSPECIFIED.

String

No

unchecked

Specifies whether this pattern will apply to unchecked methods.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No


weblogic.ejbgen.MethodPermissionPatterns

Target: Class

This annotation does not have any values, other than the array of weblogic.ejbgen.MethodPermissionPattern annotations.

weblogic.ejbgen.PrimKeyField

This tag is deprecated, use the attribute primkeyField on weblogic.ejbgen.CmpField.

weblogic.ejbgen.Relation

Target: Class

Attributes

Table E-26 Relation EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

multiplicity

Sets the multiplicity of the relationship.

Valid values for this attribute are:

  • Relation.Multiplicity.UNSPECIFIED

  • Relation.Multiplicity.ONE

  • Relation.Multiplicity.MANY

Enum

Yes

name

Specifies the name of the relationship. Use the same name on both ends of a relationship (this constraint also applies to unidirectional relationships).

String

Yes

jointTable

Deprecated. Oracle recommends that you use joinTable instead.

String

No

joinTable

Only needed in a many-to-many relationship. The name of an existing table that will be used to hold the join table containing the relationships. If you are using a compound primary key, specify a set of corresponding foreign keys separated by a comma. The default value of this attribute is UNSPECIFIED.

String

No

fkColumn

Needed only in a relationship having at least one One side. The non-One side EJB must declare the column that it will use to store the primary key of its counterpart. The default value of this attribute is UNSPECIFIED.

String

No

roleName

The name of this role (such as "ParentHasChildren"). If no role name is given, EJBGen will generate one for you. You must specify a role-name in order to inherit relations. The default value of this attribute is UNSPECIFIED.

String

No

foreignKeyTable

The name of a DBMS table that contains a foreign-key. The default value of this attribute is UNSPECIFIED.

String

No

primaryKeyTable

The name of a DBMS table that contains a primary-key. The default value of this attribute is UNSPECIFIED.

String

No

cmrField

Specifies the CMR field where this relationship will be kept. This field is optional. If it not present, the relationship is unidirectional. The default value of this attribute is UNSPECIFIED.

String

No

dbCascadeDelete

Determines whether a cascade delete will use the built-in cascade delete facilities of the underlying DBMS.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

cascadeDelete

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

targetEjb

Specifies the EJB name of the target of this relationship, which is used t generate the role name. If not supplied, a unique string will be generated. The default value of this attribute is UNSPECIFIED.

String

No

id

The identity of this tag (used for tag inheritance only). The default value of this attribute is UNSPECIFIED.

String

No


weblogic.ejbgen.Relations

Target: Class

This annotation does not have any attributes, other than the array of weblogic.ejbgen.Relation annotations.

weblogic.ejbgen.RelationshipCachingElement

Target: Class

Attributes

Table E-27 RelationshipCachingElement EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

cachingName

Specifies the name of an eager relationship caching.

String

Yes

cmrField

Specifies a comma-separated list of CMR field names.

String

Yes

groupName

Specifies the name of the group to be loaded for the CMR field. The default value of this attribute is UNSPECIFIED.

String

No

parentId

Specifies the parent ID of this element. The default value of this attribute is UNSPECIFIED.

String

No

id

The identity of this tag (used for tag inheritance only). The default value of this attribute is UNSPECIFIED.

String

No


weblogic.ejbgen.RelationshipCachingElements

Target: Class

This annotation does not have any attributes, other than the array of weblogic.ejbgen.RelationshipCachingElement annotations.

weblogic.ejbgen.RemoteHomeMethod

Target: Method

Attributes

Table E-28 RemoteHomeMethod EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

orderingNumber

Specifies the number where this method must appear in the generated class. The default value of this attribute is UNSPECIFIED.

String

No

isolationLevel

Specifies the type of transaction isolation for this method.

See Constants.IsolationLevel for valid values for this attribute. The default value is Constants.IsolationLevel.UNSPECIFIED.

Enum (Constants.IsolationLevel)

No

transactionAttribute

Specifies the transaction attribute for this remote method. If not specified, the default transaction attribute will be used. Methods with this tag will be generated on the Remote class.

See Constants.TransactionAttribute for valid values for this attribute. The default value is Constants.TransactionAttribute.UNSPECIFIED.

Enum (Constants.TransactionAttribute)

No

roles

Defines a comma-separated list of roles that are allowed to invoke this method. The default value of this attribute is UNSPECIFIED.

String

No

isIdempotent

Sets whether this method is idempotent.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

retryCount

The number of retries for this method on a rollback.

The default value of this attribute is 0.

int

No


weblogic.ejbgen.RemoteMethod

Target: Method

Attributes

Table E-29 RemoteMethod EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

orderingNumber

Specifies the number where this method must appear in the generated class. The default value of this attribute is UNSPECIFIED.

String

No

isolationLevel

Specifies the type of transaction isolation for this method.

See Constants.IsolationLevel for valid values for this attribute. The default value is Constants.IsolationLevel.UNSPECIFIED.

Enum (Constants.IsolationLevel)

No

transactionAttribute

Specifies the transaction attribute for this remote method. If not specified, the default transaction attribute will be used. Methods with this tag will be generated on the Remote class.

See Constants.TransactionAttribute for valid values for this attribute. The default value is Constants.TransactionAttribute.UNSPECIFIED.

Enum (Constants.TransactionAttribute)

No

roles

Defines a comma-separated list of roles that are allowed to invoke this method. The default value of this attribute is UNSPECIFIED.

String

No

isIdempotent

Sets whether this method is idempotent.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

retryCount

The number of retries for this method on a rollback. The default value of this attribute is 0.

int

No


weblogic.ejbgen.ResourceEnvRef

Target: Class

Attributes

Table E-30 ResourceEnvRef EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

type

Specifies the type of the environment resource references (e.g., javax.jms.Queue).

String

Yes

name

Names the resource environment reference.

String

Yes

jndiName

Gives the JNDI name of the resource. The default value of this attribute is UNSPECIFIED.

String

No

id

The identity of this tag (used for tag inheritance only). The default value of this attribute is UNSPECIFIED.

String

No


weblogic.ejbgen.ResourceEnvRefs

Target: Class

This annotation does not have any attributes, other than the array of weblogic.ejbgen.ResourceEnvRef annotations.

weblogic.ejbgen.ResourceRef

Target: Class

Attributes

Table E-31 ResourceRef EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

jndiName

Specifies the JNDI name of the resource.

String

Yes

type

Specifies the type of the resource (e.g., javax.sql.DataSource).

String

Yes

auth

Valid values for this attribute are:

  • ResourceRef.Auth.UNSPECIFIED

  • ResourceRef.Auth.APPLICATION

  • ResourceRef.Auth.CONTAINER

The default value ResourceRef.Auth.UNSPECIFIED.

Enum

No

name

Names the resource.

String

Yes

sharingScope

Defines the sharing scope.

Valid values for this attribute are:

  • ResourceRef.SharingScope.UNSPECIFIED

  • ResourceRef.SharingScope.SHAREABLE

  • ResourceRef.SharingScope.UNSHAREABLE

The default value ResourceRef.SharingScope.UNSPECIFIED.

Enum

No

id

The identity of this tag (used for tag inheritance only). The default value of this attribute is UNSPECIFIED.

String

No


weblogic.ejbgen.ResourceRefs

Target: Class

This annotation does not have any attributes, other than the array of weblogic.ejbgen.ResourceRef annotations.

weblogic.ejbgen.RoleMapping

Target: Class

Attributes

Table E-32 RoleMapping EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

roleName

Specifies the name of the role.

String

Yes

externallyDefined

True if this role is defined externally.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Note: The externallyDefined attribute must be specified if the principals attribute is not specified.

Enum (Constants.Bool)

(See description)

principals

Comma separated list of the names of the principals in this role. The default value of this attribute is UNSPECIFIED.

Note: The principals attribute must be specified if the externallyDefined attribute is not specified.

String

(See description

id

The identity of this tag (used for tag inheritance only). The default value of this attribute is UNSPECIFIED.

String

No


weblogic.ejbgen.RoleMappings

Target: Class

This annotation does not have any attributes, other than the array of weblogic.ejbgen.RoleMapping annotations.

weblogic.ejbgen.SecurityRoleRef

Target: Class

Attributes

Table E-33 SecurityRoleRef EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

roleName

Specifies the name of the security role.

String

Yes

id

The identity of this tag (used for tag inheritance only). The default value of this attribute is UNSPECIFIED.

String

No

roleLink

References a defined security role. The default value of this attribute is UNSPECIFIED.

String

No


weblogic.ejbgen.SecurityRoleRefs

Target: Class

This annotation does not have any attributes, other than the array of weblogic.ejbgen.SecurityRoleRef annotations.

weblogic.ejbgen.Select

Target: Method

Attributes

Table E-34 Select EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

cachingName

Specifies the name of an eager relationship caching. The default value of this attribute is UNSPECIFIED.

String

No

groupName

Names the group for the WebLogic Server query. The default value of this attribute is UNSPECIFIED.

String

No

maxElements

Specifies the maximum number of elements that should be returned by a multi-valued query. The default value of this attribute is UNSPECIFIED.

String

No

sqlSelectDistinct

Determines whether the generated SQL SELECT will contain a DISTINCT qualifier.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

includeUpdates

Determines whether updates made during the current transaction must be reflected in the result of a query.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

orderingNumber

Specifies the number where this method must appear in the generated class. The default value of this attribute is UNSPECIFIED.

String

No

ejbQl

Specifies the EJB-QL that defines this select method. The method name must start with ejbSelect. The default value of this attribute is UNSPECIFIED.

String

No

weblogicEjbQl

Specifies the Weblogic Server EJB-QL request as it will appear in the deployment descriptor. Note: if this request is needed, enclose both EJB-QL and Weblogic Server EJB-QL within double quotes. The default value of this attribute is UNSPECIFIED.

String

No

resultTypeMapping

Specifies whether the returned objects are mapped to EJBLocalObject or EJBObject.

Valid values for this attribute are:

  • Select.ResultTypeMapping.UNSPECIFIED

  • Select.ResultTypeMapping.LOCAL

  • Select.ResultTypeMapping.REMOTE

The default value is Select.ResultTypeMapping.UNSPECIFIED.

Enum

No


weblogic.ejbgen.ServiceEndpointMethod

Target: Method

Attributes

Table E-35 ServiceEndpointMethod EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

transactionAttribute

Specifies the Transaction Attribute for a Service Endpoint method of a Stateless Session Bean

See Constants.TransactionAttribute for valid values for this attribute. The default value is Constants.TransactionAttribute.UNSPECIFIED.

Enum (Constants.TransactionAttribute)

No

unchecked

Specifies whether this method accessible by everyone

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

roles

Specifies a comma-separated list of roles that are allowed to invoke this method. The default value for this attribute is UNSPECIFIED.

String

No


weblogic.ejbgen.ServiceRef

Target: Class

Attributes

Table E-36 ServiceRef EJBGen Annotation Attribute

AttributeDescriptionData TypeRequired?

serviceInterface

Name of this service in the WSDL file.

String

Yes


weblogic.ejbgen.ServiceRefs

Target: Class

This annotation does not have any attributes, other than the array of weblogic.ejbgen.ServiceRef annotations.

weblogic.ejbgen.Session

Target: Class

Attributes

Table E-37 Session EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

ejbName

Names this session bean.

String

Yes

isClusterable

Sets whether this bean is clusterable.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

replicationType

Specifies how to replicate stateful session beans in a cluster.

Valid values for this attribute are:

  • Session.ReplicationType.UNSPECIFIED

  • Session.ReplicationType.IN_MEMORY

  • Session.ReplicationType.NONE

The default value Session.ReplicationType.UNSPECIFIED.

Enum

No

clientsOnSameServer

Specifies whether the clients are collocated with the EJB on the same server.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

serviceEndpoint

The fully-qualified name of the enterprise beans web service endpoint interface. The default value of this attribute is UNSPECIFIED.

String

No

useCallerIdentity

Specifies whether this EJB uses callers identity.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

persistentStoreDir

Specifies the directory in which to store the passivated beans. The default value of this attribute is UNSPECIFIED.

String

No

callRouterClassName

Gives class name to be used for routing home method calls. The default value of this attribute is UNSPECIFIED.

String

No

defaultTransaction

Specifies the transaction attribute to be applied to all methods that do not have a specific transaction attribute setting.

See Constants.TransactionAttribute for valid values for this attribute. The default value is Constants.TransactionAttribute.UNSPECIFIED.

Enum (Constants.TransactionAttribute)

No

methodsAreIdempotent

Specifies whether the methods for this stateless session bean are idempotent or not.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

runAsIdentityPrincipal

Deprecated. Use runAsPrincipalName instead.

String

No

runAsPrincipalName

Gives the name of the principal in case the role maps to several principals. The default value for this attribute is UNSPECIFIED.

String

No

enableCallByReference

Specifies whether the container will call this EJB by reference.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

dispatchPolicy

Specifies the dispatch policy queue for this bean. The default value of this attribute is UNSPECIFIED.

String

No

remoteClientTimeout

Specifies the length of time that a remote RMI client will wait before it will time out. The default value of this attribute is UNSPECIFIED

String

No

passivateAsPrincipalName

Names the principal to be used when ejbPassivate would otherwise run with an anonymous principal. The default value of this attribute is UNSPECIFIED.

String

No

maxBeansInCache

Specifies the maximum number of beans in the cache. The default value of this attribute is UNSPECIFIED.

String

No

initialBeansInFreePool

Specifies the initial number of beans in the free pool. The default value of this attribute is UNSPECIFIED.

String

No

allowRemoveDuringTransaction

Specifies whether remove() can be invoked during a transaction.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

idleTimeoutSeconds

Specifies the maximum duration an EJB remains cached. The default value of this attribute is UNSPECIFIED.

String

No

type

Specifies the type of the Session bean. If this attribute is not specified, EJBGen will guess the right type by looking at the ejbCreate() methods on your class.

Valid values for this attribute are:

  • Session.SessionType.UNSPECIFIED

  • Session.SessionType.STATELESS

  • Session.SessionType.STATEFUL

The default value Session.SessionType.UNSPECIFIED.

Enum

No

removeAsPrincipalName

Names the principal to be used when ejbRemove would otherwise run with an anonymous principal.

The default value of this attribute is UNSPECIFIED.

String

No

transTimeoutSeconds

Specifies the transaction timeout (in seconds). The default value of this attribute is UNSPECIFIED.

String

No

transactionType

Specifies who manages the transactions for this EJB.

Valid values for this attribute are:

  • Session.SessionTransactionType.UNSPECIFIED

  • Session.SessionTransactionType.BEAN

  • Session.SessionTransactionType.CONTAINER

The default value Session.SessionTransactionType.UNSPECIFIED.

Enum

No

allowConcurrentCalls

Specifies whether to allow concurrent calls on that EJB.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

maxBeansInFreePool

Specifies the maximum number of beans in the free pool. The default value of this attribute is UNSPECIFIED.

String

No

sessionTimeoutSeconds

Specifies the number of seconds an EJB stays alive before being passivated. The default value of this attribute is UNSPECIFIED.

String

No

beanLoadAlgorithm

Specifies the algorithm to be used for load-balancing among replicas of this bean. The default value of this attribute is UNSPECIFIED.

String

No

homeLoadAlgorithm

Specifies the algorithm to use for load-balancing between replicas of this home.

See Constants.HomeLoadAlgorithm for valid values for this attribute. The default value is Constants.HomeLoadAlgorithm.UNSPECIFIED.

Enum (Constants.HomeLoadAlgorithm)

No

cacheType

Specifies the type of the cache for this stateful Session bean.

Valid values for this attribute are:

  • Session.CacheType.UNSPECIFIED

  • Session.CacheType.N_R_U

  • Session.CacheType.L_R_U

The default value Session.CacheType.UNSPECIFIED.

Enum

No

runAs

Specifies the role-name for this EJB. The default value of this attribute is UNSPECIFIED.

String

No

homeIsClusterable

Specifies whether this bean can be deployed from multiple servers in a cluster.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

homeCallRouterClassName

Names class to be used for routing home method calls. The default value of this attribute is UNSPECIFIED.

String

No

createAsPrincipalName

Names the principal to be used when ejbCreate would otherwise run with an anonymous principal. The default value of this attribute is UNSPECIFIED.

String

No

networkAccessPoint

Assigns a custom network channel that the EJB will use for network communications. A network channel defines a set of connection attributes. The default value of this attribute is UNSPECIFIED.

String

No


weblogic.ejbgen.SqlFinder

Target: Class

Attributes

Table E-38 SqlFinder EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

sql

Specifies the Weblogic Server EJB QL request as it will appear in the deployment descriptor.

Note: If this request is needed, enclose both EJB-QL and Weblogic Server EJB-QL within double quotes.

String

Yes

signature

Specifies exactly the signature to be generated on the Home class. EJBGen will add the conformant exceptions, but you must specify the fully qualified type of each parameter, even if it belongs to java.lang.

String

Yes

maxElements

Specifies the maximum number of elements that should be returned by a multi-valued query. The default value of this attribute is UNSPECIFIED.

String

No

includeUpdates

Determines whether updates made during the current transaction must be reflected in the result of a query.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

isolationLevel

Specifies the type of transaction isolation for this method.

See Constants.IsolationLevel for valid values for this attribute. The default value is Constants.IsolationLevel.UNSPECIFIED.

Enum (Constants.IsolationLevel)

No

dbSpecificSql

Specifies the Weblogic Server EJB QL request as it will appear in the deployment descriptor. Note: if this request is needed, enclose both EJB-QL and Weblogic Server EJB-QL within double quotes.

Valid value for this attribute is an array of weblogic.ejbgen.DBSpecificSQL annotations. The default value is an empty array.

Array of weblogic.ejbgen.DBSpecificSQL

No

sqlShapeName

Specifies the EJB QL request as it will appear in the deployment descriptor. The default value of this attribute is UNSPECIFIED.

String

No

transactionAttribute

Specifies thetransaction attribute for this local method. If not specified, the default transaction attribute will be used. Methods with this tag will be generated on the Local class.

See Constants.TransactionAttribute for valid values for this attribute. The default value is Constants.TransactionAttribute.UNSPECIFIED.

Enum ( Constants.TransactionAttribute)

No

generateOn

Determines which Home this finder will be generated on. If unspecified, it will be generated on both.

Valid values for this attribute are:

  • SqlFinder.GenerateOn.UNSPECIFIED

  • SqlFinder.GenerateOn.LOCAL

  • SqlFinder.GenerateOn.REMOTE

The default value SqlFinder.GenerateOn.UNSPECIFIED.

Enum

No

sqlSelectDistinct

Determines whether the generated SQL SELECT will contain a DISTINCT qualifier.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No

enableQueryCaching

Controls whether read-only entity EJBs can be cached at the query level.

See Constants.Bool for valid values for this attribute. The default value is Constants.Bool.UNSPECIFIED.

Enum (Constants.Bool)

No


weblogic.ejbgen.SqlFinders

Target: Class

This annotation does not have any attributes, other than the array of weblogic.ejbgen.SqlFinder annotations.

weblogic.ejbgen.SqlShape

Target: Class

Attributes

Table E-39 SqlShape EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

name

Specifies exactly the signature to be generated on the Home class. EJBGen will add the conformant exceptions, but you must specify the fully-qualified type of each parameter, even if it belongs to java.lang.

String

Yes

relationNames

Name of the SQL Shape to use for this finder query The default value of this attribute is an empty array.

Array of String

No

tables

Name of the SQL Shape to use for this finder query. The default value of this attribute is an empty array.

Array of weblogic.ejbgen.SqlShapeTable

No

passThroughColumns

Name of the SQL Shape to use for this finder query. The default value of this attribute is 0.

int

No


weblogic.ejbgen.SqlShapeTable

Target: Class, Method, Field

Attributes

Table E-40 SqlShapeTable EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

name

The name of the SQL shape table.

String

Yes

ejbRelationshipRoleName

The name of the relationship role. The default value of this attribute is UNSPECIFIED.

String

No

columns

Database columns.

Array of String

Yes


weblogic.ejbgen.SqlShapes

Target: Class

This annotation does not have any attributes, other than the array of weblogic.ejbgen.SqlShape annotations.

weblogic.ejbgen.ValueObject

Target: Class

Attributes

Table E-41 ValueObject EJBGen Annotation Attribute

AttributeDescriptionData TypeRequired?

reference

Specifies what objects the value object class should reference when accessing other EJBs.

Valid values for this attribute are:

  • ValueObject.Reference.UNSPECIFIED

  • ValueObject.Reference.UNSPECIFIED

  • ValueObject.Reference.UNSPECIFIED

Default value is ValueObject.Reference.UNSPECIFIED.

Enum

No


weblogic.ejbgen.ValueObjectField

Target: Class, Method, Field

Attributes

Table E-42 ValueObjectField EJBGen Annotation Attributes

AttributeDescriptionData TypeRequired?

int

The default value of this attribute is 0.

int

No


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5 Session EJBs

This section describes how session beans work within the EJB container, and provides design and development guidelines that are specific to session beans. For a description of the overall bean development process, see Implementing Enterprise JavaBeans.

It is assumed that the reader is familiar with Java programming and session bean features and capabilities. For an introduction to session bean features and how they are typically used in applications, see Session EJBs Implement Business Logic and Session Bean Features.

The following sections describe the session bean life-cycle, design considerations, and instructions for key implementation tasks.

Comparing Stateless and Stateful Session Beans

This section compares the key differences between stateless and stateful session beans.

Table 5-1 Comparing Stateless and Stateful Session Beans

Stateless Session BeansStateful Sessions Beans

Are pooled in memory, to save the overhead of creating a bean every time one is needed. WebLogic Server uses a bean instance when needed and puts it back in the pool when the work is complete.

Stateless sessions beans provide faster performance than stateful beans.

Each client creates a new instance of a bean, and eventually removes it. Instances may be passivated to disk if the cache fills up.

An application issues an ejbRemove() to remove the bean from the cache.

Stateful sessions beans do not perform as well as stateless sessions beans.

Have no identity and no client association; they are anonymous.

Are bound to particular client instances.Each bean has an implicit identity. Each time a client interacts with a stateful session bean during a session, it is the same object.

Do not persist. The bean has no state between calls.

Persist. A stateful session bean's state is preserved for the duration of a session.


See Choosing Between Stateless and Stateful Beans for a discussion of when to use which type of session bean.

Pooling for Stateless Session EJBs

By default, no stateless session EJB instances exist in WebLogic Server at startup time. As individual beans are invoked, WebLogic Server initializes new instances of the EJB.

However, in a production environment, WebLogic Server can provide improved performance and throughput for stateless session EJBs by maintaining a free pool of unbound stateless session EJBs—instances that are not currently processing a method call. If an unbound instance is available to serve a request, response time improves, because the request does not have to wait for an instance to be created. The free pool improves performance by reusing objects and skipping container callbacks when it can.

Upon startup, WebLogic Server automatically creates and populates the free pool with the quantity of instances you specify in the bean's initial-beans-in-free-pool deployment element in the weblogic-ejb-jar.xml file. By default, initial-beans-in-free-pool is set to 0.

Additionally, in this release of WebLogic Server, Administrators can initialize EJB pools on demand via the Administration Console. When an EJB's pool is initialized, it is reset to the state it was in immediately after the EJB was deployed. For more information, see "Initialize the idle bean cache and pool of an EJB" in Oracle WebLogic Server Administration Console Help.

The following figure illustrates the WebLogic Server free pool, and the processes by which stateless EJBs enter and leave the pool. Dotted lines indicate the "state" of the EJB from the perspective of WebLogic Server.

Figure 5-1 WebLogic Server Free Pool Showing Stateless Session EJB Life Cycle

Description of Figure 5-1 follows

If you configure a pool, WebLogic Server will service method calls with an EJB instance from the free pool, if one is available. The EJB remains active for the duration of the client's method call. After the method completes, the EJB instance is returned to the free pool. Because WebLogic Server unbinds stateless session beans from clients after each method call, the actual bean class instance that a client uses may be different from invocation to invocation.

If all instances of an EJB class are active and max-beans-in-free-pool has been reached, new clients requesting the EJB class will be blocked until an active EJB completes a method call. If the transaction times out (or, for non-transactional calls, if five minutes elapse), WebLogic Server throws a RemoteException for a remote client or an EJBException for a local client.


Note:

The maximum size of the free pool is limited by the value of the max-beans-in-free-pool element, available memory, or the number of execute threads.

You can configure the WebLogic Server to remove bean instances that have remained unused in the pool for a period of time specified in idle-timeout-seconds element in the pool element. When beans have been in the pool unused for the amount of time you specify in idle-timeout-seconds, they are removed from the pool until the number of beans in the pool reaches the number specified in initial-beans-in-free-pool; the number of beans in the pool will never fall below the number specified in initial-beans-in-free-pool.

When an application requests a bean instance from the free pool, there are three possible outcomes:

  • An instance is available in the pool. WebLogic Server makes that instance available and your application proceeds with processing.

  • No instance is available in the pool, but the number of instances in use is less than max-beans-in-free-pool. WebLogic Server allocates a new bean instance and gives it to you.

  • No instances are available in the pool and the number of instances in use is already max-beans-in-free-pool. Your application must wait until either your transaction times out or a bean instance that already exists in the pool becomes available.

Caching and Passivating Stateful Session EJBs

WebLogic Server uses a cache of bean instances to improve the performance of stateful session EJBs. The cache stores active EJB instances in memory so that they are immediately available for client requests. The cache contains EJBs that are currently in use by a client and instances that were recently in use. Stateful session beans in cache are bound to a particular client.

The following figure illustrates the WebLogic Server cache, and the processes by which stateful EJBs enter and leave the cache.

Figure 5-2 Stateful Session EJB Life Cycle

Description of Figure 5-2 follows

Stateful Session EJB Creation

No stateful session EJB instances exist in WebLogic Server at startup. Before a client begins accessing a stateful session bean, it creates a new bean instance to use during its session with the bean. When the session is over the instance is destroyed. While the session is in progress, the instance is cached in memory.

Stateful Session EJB Passivation

Passivation is the process by which WebLogic Server removes an EJB instance from cache while preserving its state on disk. While passivated, EJBs are not in memory and are not immediately available for client requests, as they are when in the cache.

The EJB developer must ensure that a call to the ejbPassivate() method leaves a stateful session bean in a condition such that WebLogic Server can serialize its data and passivate the instance. During passivation, WebLogic Server attempts to serialize any fields that are not declared transient. This means that you must ensure that all non-transient fields represent serializable objects, such as the bean's remote or home interface. EJB 2.1 specifies the field types that are allowed.

Controlling Passivation

The rules that govern the passivation of stateful session beans vary, based on the value of the beans cache-type element, which can be:

  • LRU—least recently used, or eager passivation.

  • NRU—not recently used, or as lazy passivation

The idle-timeout-seconds and max-beans-in-cache elements also affect passivation and removal behaviors, based on the value of cache-type.

Eager Passivation (LRU)

When you configure eager passivation for a stateful session bean by setting cache-type to LRU, the container passivates instances to disk:

  • As soon as an instance has been inactive for idle-timeout-seconds, regardless of the value of max-beans-in-cache.

  • When max-beans-in-cache is reached, even though idle-timeout-seconds has not expired.

The container removes a passivated instance from disk after it has been inactive for idle-timeout-seconds after passivation. This is referred to as a lazy remove.


Note:

ejbRemove may not be called on bean instances that are deleted after idle-timeout-seconds is reached.

Lazy Passivation (NRU)

When lazy passivation is configured by setting cache-type to NRU, the container avoids passivating beans, because of the associated systems overhead—pressure on the cache is the only event that causes passivation or eager removal of beans.

When the cache is full and a bean instance must be removed from the cache to make room for another instance, the container:


Note:

ejbRemove may not be called on bean instances that are deleted after idle-timeout-seconds is reached.

  • Removes the bean instance from the cache without passivating it to disk if idle-timeout-seconds has expired. This is referred to as a eager remove. An eager remove ensures that an inactive instance does not consume memory or disk resources.

  • Passivates the bean instance to disk if idle-timeout-seconds has not expired.

Specifying the Persistent Store Directory for Passivated Beans

When a stateful session bean is passivated, its state is stored in a file system directory. Each server instance has its own directory for storing the state of passivated stateful session beans, known as the persistent store directory. The persistent store directory contains one subdirectory for each passivated bean.

The persistent store directory is created by default in the server instance directory, for example:

D:\releases\<version>\bea\user_domains\mydomain\myserver\tmp\pstore\

The path to the persistence store is:

RootDirectory\ServerName\persistent-store-dir

where:

  • RootDirectory—the directory where WebLogic Server runs.

    RootDirectory can be specified at server startup with the -Dweblogic.RootDirectory property.

  • ServerName—the name of the server instance.

  • persistent-store-dir—the value of the of the persistent-store-dir element in the <stateful-session-descriptor> element of weblogic-ejb-jar.xml. If no value is specified for <persistent-store-dir>, the directory is named pstore by default.

The persistent store directory contains a subdirectory, named with a hash code, for each passivated bean. For example, the subdirectory for a passivated bean in the example above might be:

D:\releases\810\bea\user_domains\mydomain\myserver\pstore\14t89gex0m2fr

Configuring Concurrent Access to Stateful Session Beans

In accordance with the EJB 2.x specification, simultaneous access to a stateful session EJB results in a RemoteException. This access restriction on stateful session EJBs applies whether the EJB client is remote or internal to WebLogic Server. To override this restriction and configure a stateful session bean to allow concurrent calls, set the allow-concurrent-calls deployment element.

If multiple servlet classes access a stateful session EJB, each servlet thread (rather than each instance of the servlet class) must have its own session EJB instance. To prevent concurrent access, a JSP/servlet can use a stateful session bean in request scope.

Design Decisions for Session Beans

This section discusses some design decisions relevant to session beans.

Choosing Between Stateless and Stateful Beans

Stateless session beans are a good choice if your application does not need to maintain state for a particular client between business method calls. WebLogic Server is multi-threaded, servicing multiple clients simultaneously. With stateless session beans, the EJB container is free to use any available, pooled bean instance to service a client request, rather than reserving an instance for each client for the duration of a session. This results in greater resource utilization, scalability and throughput.

Stateless session beans are preferred for their light-weight implementation. They are a good choice if your application's beans perform autonomous, distinct tasks without bean-to-bean interaction.

Stateful session beans are a good choice if you need to preserve the bean's state for the duration of the session.

For examples of applications of stateless and stateful session beans, see Stateless Session Beans and Stateful Session Beans.

Choosing the Optimal Free Pool Setting for Stateless Session Beans

When you choose values for initial-beans-in-free-pool and max-beans-in-free-pool you must weigh memory consumption against slowing down your application. If the number of stateless session bean instances is too high, the free pool contains inactive instances that consume memory. If the number is too low, a client may not obtain an instance when it needs it. This leads to client threads blocking until an instance frees up, slowing down the application.

Usually max-beans-in-free-pool should be equal to the number of worker threads in the server instance, so that when a thread tries to do work an instance is available.

Implementing Session Beans

Chapter 4 takes you through session bean implementation step-by-step. This section explains the details of configuring WebLogic-Server specific session bean behavior by setting bean-specific deployment descriptor elements.

WebLogic-Specific Configurable Behaviors for Session Beans

Table 5-2 summarizes the deployment descriptor elements you set to configure the behavior of a stateless session bean and how the bean behaves if you do not configure the element. All of the elements listed are sub-elements of the stateless-session-descriptor element in weblogic-ejb-jar.xml.

Table 5-3 summarizes the deployment descriptor elements you set to configure the behavior of a stateful session bean and how the bean behaves if you do not configure the element. All of the elements listed are sub-elements of the stateful-session-descriptor element in weblogic-ejb-jar.xml.

Table 5-2 WebLogic-Specific Features for Stateless Session EJBs

To controlSet the following weblogic-ejb-jar.xml elementDefault behavior

The number of inactive instances of a stateless session bean that exist in WebLogic Server when it is started.

See Pooling for Stateless Session EJBs.

initial-beans-in-free-pool


WebLogic Server creates 0 beans in the free pool.

The number of seconds a bean can be idle in the pool before WebLogic Server can remove it.

Note: Idle beans can only be removed from the pool until the number of beans in the pool reaches initial-beans-in-free-pool.

idle-timeout-seconds


WebLogic Server removes beans from the free pool when they have been idle for 600 seconds.

The maximum size of the free pool of inactive stateless session beans.

max-beans-in-free-pool


WebLogic Server limits the maximum number of beans in the free pool to 1000.

How WebLogic Server replicates stateless session EJB instances in a cluster.

See Reliability and Availability Features.


The EJB can be deployed to multiple servers in a cluster.


Table 5-3 WebLogic-Specific Features for Stateful Session EJBs

Behaviorweblogic-ejb-jar.xml elementDefault

Whether multiple clients can simultaneously access a bean without triggering a Remote Exception.

See Configuring Concurrent Access to Stateful Session Beans.

allow-concurrent-calls


False—The server throws a RemoteException when a stateful session bean instance is currently handling a method call and another (concurrent) method call arrives on the server.

Whether the EJB container can remove a stateful session bean within a transaction context without provoking an error.

allow-remove-during-transaction

False—The server throws an exception when a stateful session bean is removed within a transaction context.

The number of stateful been instances that can exist in cache.

max-beans-in-cache


1000

The period of inactivity before a stateful session bean instance remains in cache (given that max-beans-in-cache has not been reached), and after passivation, remains on disk.

idle-timeout-seconds


600 seconds

The rules for removing a stateful session bean instance from the cache.

cache-type


NRU (not recently used)—For a description of this behavior, see Lazy Passivation (NRU).

Where WebLogic Server stores the state of passivated stateful session bean instances.

persistent-store-dir


pstore

To support method failover, specify the idempotent methods for a clustered EJB. An idempotent method can be repeated with no negative side-effects.

idempotent-methods


None

Custom class to be used for routing home method calls.

home-call-router-class-name

None

Indicates if the bean home can be clustered.

home-is-clusterable


True

Algorithm to use for load-balancing among replicas of the bean home.

home-load-algorithm


Algorithm specified by the property weblogic.cluster.defaultLoadAlgorithm

Indicates the replication used for stateful session beans in a cluster: in-memory or none.

replication-type


None


PK#=("~~PK;wE OEBPS/toc.ncxW Oracle® Fusion Middleware Programming Enterprise JavaBeans for Oracle WebLogic Server, 11g Release 1 (10.3.6) Cover Title and Copyright Information Contents Preface 1 Introduction and Roadmap 2 Understanding Enterprise JavaBeans 3 Designing Enterprise JavaBeans 4 Implementing Enterprise JavaBeans 5 Session EJBs 6 Entity EJBs 7 Message-Driven EJBs 8 Deployment Guidelines for Enterprise JavaBeans A Deployment Descriptor Schema and Document Type Definitions Reference B weblogic-ejb-jar.xml Deployment Descriptor Reference C weblogic-cmp-jar.xml Deployment Descriptor Reference D appc Reference E EJBGen Reference F Important Information for EJB 1.1 Users G EJB Query Language (EJB-QL) and WebLogic Server Copyright PK- \WPK;wEOEBPS/content.opf Oracle® Fusion Middleware Programming Enterprise JavaBeans for Oracle WebLogic Server, 11g Release 1 (10.3.6) en-US E13719-06 Oracle Corporation Oracle Corporation Oracle® Fusion Middleware Programming Enterprise JavaBeans for Oracle WebLogic Server, 11g Release 1 (10.3.6) 2011-11-03T11:53:04Z This document is a resource for software developers who develop applications that include WebLogic Server Enterprise Java Beans (EJBs). PK:;PK;wEOEBPS/implementing.htm Implementing Enterprise JavaBeans

4 Implementing Enterprise JavaBeans

The sections that follow describe the EJB implementation process, and provide guidance for how to get an EJB up and running in WebLogic Server.

It is assumed that you understand WebLogic Server's value-added EJB features, have selected a design pattern for your application, and have made key design decisions.

For a review of WebLogic Server EJB features, see WebLogic Server Value-Added EJB Features.

For discussion of design options for EJBs, factors to consider during the design process, and recommended design patterns see Designing Enterprise JavaBeans.

Overview of the EJB Development Process

This section is a brief overview of the EJB development process. It describes the key implementation tasks and associated results.

Figure 4-1 illustrates the process of developing an EJB. The steps in the process, and the results of each are described in Table 4-1. Subsequent sections detail each step in the process.

Figure 4-1 EJB Development Process Overview

Description of Figure 4-1 follows

Table 4-1 EJB Development Tasks and Results

StepDescriptionResult

Create a Source Directory


Create the directory structure for your source files, deployment descriptors, and files that are generated during the implementation process.

A directory structure on your local drive.

Create EJB Classes and Interfaces


Create the classes that make up your bean. Insert appropriate tags in your source code to enable automatic generation of deployment descriptor elements later in the implementation process.

.java file for each class

Compile Java Source


Compile source code.

.class file for each class

Generate Deployment Descriptors


Write or generate deployment descriptors that configure the runtime behavior and environment for the bean.

ejb-jar.xml, and optionally:

  • weblogic-ejb-jar.xml, which contains elements that control WebLogic Server-specific features, and

  • weblogic-cmp-jar.xml, if the bean is a container-managed persistence entity bean.

Edit Deployment Descriptors


You may need to edit deployment descriptors to ensure they correctly reflect all desired runtime behaviors for your bean.

If your source was thoroughly annotated with markup that specifies the optional features the bean uses, and you used EJBGen to generate the deployment descriptors automatically, edits to your deployment descriptor should be minimal.

  • ejb-jar.xml,

  • weblogic-ejb-jar.xml, which contains elements that control WebLogic Server-specific features, and

  • weblogic-cmp-jar.xml, if the bean is a container-managed persistence entity bean.

Generate EJB Wrapper Classes, and Stub and Skeleton Files


Generate the container classes used to access the deployment unit, including classes for home and remote interfaces.

Generated classes are added to archive or directory.

Package


Package compiled files, generated files, and deployment descriptors for deployment.

If appropriate, you can leave your files unarchived in an exploded directory.

Archive, either a JAR or an EAR

Deploy


Target the archive or application directory to desired Managed Server, or a WebLogic Server cluster, in accordance with selected staging mode.

The deployment settings for the bean are written to EJBComponent element in config.xml.


Create a Source Directory

Create a source directory where you will assemble the EJB.

Oracle recommends a split development directory structure, which segregates source and output files in parallel directory structures. For instructions on how to set up a split directory structure and package your EJB as an enterprise application archive (EAR), see "Overview of the Split Development Directory Environment" in Developing Applications for Oracle WebLogic Server.

If you prefer to package and deploy your EJB in a JAR file, create a directory for your class files, and within that directory, a subdirectory named META-INF for deployment descriptor files.

Example 4-1 Directory Structure for Packaging JAR

myEJB/
    META-INF/
   ejb-jar.xml
        weblogic-ejb-jar.xml
        weblogic-cmp-jar.xml
    foo.class
    fooHome.class
    fooBean.class

Create EJB Classes and Interfaces

The classes required depend on the type of EJB you are developing, as described in EJB Components..

Oracle offers productivity tools for developing class and interface files. The EJBGen command line utility automates the process of creating class and interface files, and also generates deployment descriptor files for the EJB. For more information and instructions for using these tools see EJBGen Reference.

The sections that follow provide tips and guidelines for using WebLogic Server-specific EJB features.

Using WebLogic Server Generic Bean Templates

For each EJB type, WebLogic Server provides a generic class that contains Java callbacks, or listeners, that are required for most EJBs. The generic classes are in the weblogic.ejb package:

  • GenericEnterpriseBean

  • GenericEntityBean

  • GenericMessageDrivenBean

  • GenericSessionBean

You can implement a generic bean template in a class of your own by importing the generic class into the class you are writing. This example imports the GenericSessionBean class into HelloWorldEJB:

import weblogic.ejb.GenericSessionBean;
     ...     
public class HelloWorldEJB extends GenericSessionBean { 

Programming Client Access to EJBs

The following sections provide guidelines for programming client access to an EJB.

Programming Client to Obtain Initial Context

Local clients obtain initial context using the getInitialContext method, similar to the following excerpt.

Example 4-2 Local Client Performing a Lookup

...
Context ctx = getInitialContexLt("t3://localhost:7001", "user1", "user1Password");
...
static Context getInitialContext(String url, String user, String password) { 
    Properties h = new Properties();
        "weblogic.jndi.WLInitialContextFactory");
    h.put(Context.PROVIDER_URL, url);
    h.put(Context.SECURITY_PRINCIPAL, user);
    h.put(Context.SECURITY_CREDENTIALS, password); 

    return new InitialContext(h);
}

Remote clients obtain an InitialContext from the WebLogic Server InitialContext factory.

Programming Client to Look Up a Home Interface

A client can look up the entity bean's home interface in one of two ways:

  • By following an EJB reference. This approach offers better performance than the alternative, looking up the home interface directly from the Java Naming and Directory Interface, and is a Oracle best practice. For instructions on using EJB references, see the following section, Using EJB Links.

  • Directly from the Java Naming and Directory Interface (JNDI). The container binds the entity bean's home interface in the global, server-side JNDI name space. For instructions see Programming JNDI for Oracle WebLogic Server.

Using EJB Links

Using EJB links is a Oracle best practice and WebLogic Server fully supports EJB links as defined in the EJB 2.1 Specification. You can link an EJB reference that is declared in one application component to an enterprise bean that is declared in the same Java EE application.

In the ejb-jar.xml file, specify the link to the EJB using the ejb-link element of the ejb-ref element of the referencing application component. The value of ejb-link must match that of the ejb-name in both ejb-jar.xml and weblogic-ejb-jar.xml of the target EJB. The target EJB can be in any EJB JAR file in the same Java EE application as the referencing application component.

Because ejb-names are not required to be unique across EJB JAR files, you may need to provide the qualified path for the link. Use the following syntax to provide the path name for the EJBs within the same Java EE application.

<ejb-link>../products/product.jar#ProductEJB</ejb-link>

This reference provides the path name of the EJB JAR file that contains the referenced EJB with the appended ejb-name of the target bean separated from the path by "#". The path name is relative to the referencing application component JAR file.

Configuring EJBs to Send Requests to a URL

To enable an EJB to open an HttpURLConnection to an external HTTP server using the java.net.URL resource manager connection factory type, specify the URL, or specify an object bound in the JNDI tree that maps to a URL, using the resource-ref element in ejb-jar.xml and the res-ref-name element in weblogic-ejb-jar.xml.

Specifying an HTTP Resource by URL

To specify the URL to which an EJB sends requests:

  1. In ejb-jar.xml, specify the URL in the <jndi-name> element of the resource-ref element.

  2. In weblogic-ejb-jar.xml, specify the URL in the <jndi-name> element of the resource-description element:

    <resource-description>
        <res-ref-name>url/MyURL</res-ref-name>
        <jndi-name>http://www.rediff.com/</jndi-name>
    </resource-description>
    

    WebLogic Server creates a URL object with the jndi-name provided and binds the object to the java:comp/env.

Specifying an HTTP Resource by Its JNDI Name

To specify an object that is bound in JNDI and maps to a URL, instead of specifying a URL:

  1. In ejb-jar.xml, specify the name by which the URL is bound in JNDI in the <jndi-name> element of the resource-ref element.

  2. In weblogic-ejb-jar.xml, specify the name by which the URL is bound in JNDI in the <jndi-name> element of the resource-description element:

    <resource-description>
        <res-ref-name>url/MyURL1</res-ref-name>
        <jndi-name>firstName</jndi-name>
    </resource-description>
    

    where firstName is the object bound to the JNDI tree that maps to the URL. This binding could be done in a startup class. When jndi-name is not a valid URL, WebLogic Server treats it as an object that maps to a URL and is already bound in the JNDI tree, and binds a LinkRef with that jndi-name.

Accessing HTTP Resources from Bean Code

Regardless of how you specified an HTTP resource—by its URL or a JNDI name that maps to the URL—you can access it from EJB code in this way:

URL url = (URL) context.lookup("java:comp/env/url/MyURL");
connection = (HttpURLConnection)url.openConnection();

Configuring Network Communications for an EJB

You can control the attributes of the network connection an EJB uses for communications by configuring a custom network channel and assigning it to the EJB. For information about WebLogic Server network channels and associated configuration instructions see "Configure Network Resources" in Configuring Server Environments for Oracle WebLogic Server. After you configure a custom channel, assign it to an EJB using the network-access-point element in weblogic-ejb-jar.xml.

Programming and Configuring Transactions

Transaction design decisions are discussed in Transaction Design and Management Options. The following sections contain guidelines for programming transactions.

For information using transactions with entity beans, see Understanding ejbLoad() and ejbStore() Behavior.

Programming Container-Managed Transactions

Container-managed transactions are simpler to program than bean-managed transactions, because they leave the job of demarcation—starting and stopping the transaction—to the EJB container.

You configure the desired transaction behaviors in ejb-jar.xml and weblogic-ejb-jar.xml. For related information see Container-Managed Transactions Elements.

Key programming guidelines for container-managed transactions include:

  • Preserve transaction boundaries—Do not invoke methods that interfere with the transaction boundaries set by the container. Do not use:

    • The commit, setAutoCommit, and rollback methods of java.sql.Connection

    • The getUserTransaction method of javax.ejb.EJBContext

    • Any method of javax.transaction.UserTransaction

  • Roll back transactions explicitly—To cause the container to roll back a container-managed transaction explicitly, invoke the setRollbackOnly method of the EJBContext interface. (If the bean throws an application exception, typically an EJBException, the rollback is automatic.)

  • Avoid serialization problems—Many data stores provide limited support for detecting serialization problems, even for a single user connection. In such cases, even with transaction-isolation in weblogic-ejb-jar.xml set to TransactionSerializable, exceptions or rollbacks in the EJB client might occur if contention occurs between clients for the same rows. To avoid such exceptions, you can:

    • Include code in your client application to catch SQL exceptions, and resolve them appropriately; for example, by restarting the transaction.

    • For Oracle databases, use the transaction isolation settings described in isolation-level.

Configuring Automatic Retry of Container-Managed Transactions

In this release of WebLogic Server, you can specify that, if a business method that has started a transaction fails because of a transaction rollback that is not related to a system exception, the EJB container will start a new transaction and retry the failed method up to a specified number of times. If the method fails for the specified number of retry attempts, the EJB container throws an exception.


Note:

The EJB container does not retry any transactions that fail because of system exception-based errors.

To configure automatic retry of container-managed transactions:

  1. Make sure your bean is a container-managed session or entity bean.

    You can configure automatic retry of container-managed transactions for container-managed session and entity beans only. You cannot configure automatic retry of container-managed transactions for message-driven beans because MDBs do not acknowledge receipt of a message they are processing when the transaction that brackets the receipt of the message is rolled back; messages are automatically retried until they are acknowledged. You also cannot configure automatic retry of container-managed transactions for timer beans because, when a timer bean's ejbTimeout method starts and is rolled back, the timeout is always retried.

  2. Make sure the business methods for which you want to configure automatic retry of transactions are defined in the bean's remote or local interface or as home methods (local home business logic that is not specific to a particular bean instance) in the home interface; the methods must have one of the following container-managed transaction attributes:

    • RequiresNew. If a method's transaction attribute (trans-attribute element in ejb-jar.xml) is RequiresNew, a new transaction is always started prior to the invocation of the method and, if configured, automatic retry of transactions occurs if the transaction fails.

    • Required. If a method's transaction attribute (trans-attribute element in ejb-jar.xml) is Required, the method is retried with a new transaction only if the failed transaction was begun on behalf of the method.

    For more information on:

  3. Make sure the methods for which you want to enable automatic retry of transactions are safe to be re-invoked. A retry of a failed method must yield results that are identical to the results the previous attempt, had it been successful, would have yielded. In particular:

    • If invoking a method initiates a call chain, it must be safe to reinvoke the entire call chain when the method is retried.

    • All of the method's parameters must be safe for reuse; when a method is retried, it is retried with the same parameters that were used to invoke the failed attempt. In general, parameters that are primitives, immutable objects, or are references to read-only objects are safe for reuse. If a parameter is a reference to an object that is to be modified by the method, reinvoking the method must not negatively affect the result of the method call.

    • If the bean that contains the method that is being retried is a stateful session bean, the bean's conversational state must be safe to re-invoke. Since a stateful session bean's state is not transactional and is not restored during a transaction rollback, in order to use the automatic retry of transactions feature, you must first be sure the bean's state is still valid after a rollback.

  4. Specify the methods for which you want the EJB container to automatically retry transactions and the number of retry attempts you want the EJB container to make in the retry-methods-on-rollback element in weblogic-ejb-jar.xml.

    The retry-count subelement to retry-methods-on-rollback can also be modified via the Administration Console.

Programming Bean-Managed Transactions

This section contains programming considerations for bean-managed transactions. For a summary of the distinguishing features of bean-level transactions and a discussion of related design considerations, see Bean-Level Transaction Management.

  • Demarcate transaction boundaries—To define transaction boundaries in EJB or client code, you must obtain a UserTransaction object and begin a transaction before you obtain a Java Transaction Service (JTS) or JDBC database connection. To obtain the UserTransaction object, use this command:

    ctx.lookup("javax.transaction.UserTransaction");
    

    After obtaining the UserTransaction object, specify transaction boundaries with tx.begin(), tx.commit(), tx.rollback().

    If you start a transaction after obtaining a database connection, the connection has no relationship to the new transaction, and there are no semantics to "enlist" the connection in a subsequent transaction context. If a JTS connection is not associated with a transaction context, it operates similarly to a standard JDBC connection that has autocommit equal to true, and updates are automatically committed to the datastore.

    Once you create a database connection within a transaction context, that connection is reserved until the transaction commits or rolls back. To optimize performance and throughput, ensure that transactions complete quickly, so that the database connection can be released and made available to other client requests.


    Note:

    You can associate only a single database connection with an active transaction context.

  • Setting transaction isolation level—For bean-managed transactions, you define isolation level in the bean code. Allowable isolation levels are defined on the java.sql.Connection interface. F or information on isolation level behaviors, see isolation-level.

    See Example 4-3 for a code sample.

Example 4-3 Setting Transaction Isolation Level in BMT

import javax.transaction.Transaction;
import java.sql.Connection
import weblogic.transaction.TxHelper:
import weblogic.transaction.Transaction;
import weblogic.transaction.TxConstants;
User Transaction tx = (UserTransaction)
ctx.lookup("javax.transaction.UserTransaction");
//Begin user transaction
    tx.begin();
//Set transaction isolation level to TransactionReadCommitted
Transaction tx = TxHelper.getTransaction();
    tx.setProperty (TxConstants.ISOLATION_LEVEL, new Integer
    (Connection.TransactionReadCommitted));
//perform transaction work 
    tx.commit();
  • Avoid restricted methods—Do not invoke the getRollbackOnly and setRollbackOnly methods of the EJBContext interface in bean-managed transactions. These methods should be used only in container-managed transactions. For bean-managed transactions, invoke the getStatus and rollback methods of the UserTransaction interface.

  • Use one connection per active transaction context—You can associate only a single database connection with an active transaction context.

Programming Transactions That Are Distributed Across EJBs

This section describes two approaches for distributing a transaction across multiple beans, which may reside on multiple server instances.

Calling multiple EJBs from a client's transaction context

The code fragment below is from a client application that obtains a UserTransaction object and uses it to begin and commit a transaction. The client invokes two EJBs within the context of the transaction.

import javax.transaction.*;
...
u = (UserTransaction) jndiContext.lookup("javax.transaction.UserTransaction");
u.begin();
account1.withdraw(100);
account2.deposit(100);
u.commit();
...

The updates performed by the account1 and account2 beans occur within the context of a single UserTransaction. The EJBs commit or roll back together, as a logical unit, whether the beans reside on the same server instance, different server instances, or a WebLogic Server cluster.

All EJBs called from a single transaction context must support the client transaction—each beans' trans-attribute element in ejb-jar.xml must be set to Required, Supports, or Mandatory.

Using an EJB "Wrapper" to Encapsulate a Cross-EJB Transaction

You can use a "wrapper" EJB that encapsulates a transaction. The client calls the wrapper EJB to perform an action such as a bank transfer, and the wrapper starts a new transaction and invokes one or more EJBs to do the work of the transaction.

The wrapper EJB can explicitly obtain a transaction context before invoking other EJBs, or WebLogic Server can automatically create a new transaction context, if the wrapper's trans-attribute element in ejb-jar.xml is set to Required or RequiresNew.

All EJBs invoked by the wrapper EJB must support the wrapper EJB's transaction context— their trans-attribute elements must be set to Required, Supports, or Mandatory.

Programming the EJB Timer Service

WebLogic Server supports the EJB timer service defined in the EJB 2.1 Specification and EJB 3.0 Specification. The EJB timer service is an EJB-container provided service that allows you to create timers that schedule callbacks to occur when a timer object expires. Timer objects can be created for entity beans, message-driven beans, and stateless session beans. Timer objects expire at a specified time, after an elapsed period of time, or at specified intervals. For instance, you can use the timer service to send out notification when an EJB remains in a certain state for an elapsed period of time.

The WebLogic EJB timer service is intended to be used as a coarse-grained timer service. Rather than having a large number of timer objects performing the same task on a unique set of data, Oracle recommends using a small number of timers that perform bulk tasks on the data. For example, assume you have an EJB that represents an employee's expense report. Each expense report must be approved by a manager before it can be processed. You could use one EJB timer to periodically inspect all pending expense reports and send an email to the corresponding manager to remind them to either approve or reject the reports that are waiting for their approval.

Clustered Versus Local EJB Timer Services

You can configure two types of EJB timer services: clustered or local.

Clustered EJB Timer Services

Clustered EJB timer services provide the following advantages:

  • Better visibility.

    Timers are accessible from any node in a cluster. For example, the javax.ejb.TimerService.getTimers() method returns a complete list of all stateless session or message-driven bean timers in a cluster that were created for the EJB. If you pass the primary key of the entity bean to the getTimers() method, a list of timers for that entity bean are returned.

  • Automatic load balancing and failover.

    Clustered EJB timer services take advantage of the load balancing and failover capabilities of the Job Scheduler.

For information about the configuring a clustered EJB timer service, see Configuring Clustered EJB Timers.

Local EJB Timer Services

Local EJB timer services execute only on the server on which they are created and are visible only to the beans on that server. With a local EJB timer service, you do not have to configure a cluster, database, JDBC data source, or leasing service, as you do for clustered EJB timer services.

You cannot migrate a local EJB timer object from one server to another; timer objects can only be migrated as part of an entire server. If a server that contains EJB timers goes down for any reason, you must restart the server or migrate the entire server in order for the timers to execute.

Using Java Programming Interfaces to Program Timer Objects

This section summarizes the Java programming interfaces defined in the EJB 2.1 Specification that you can use to program timers. For detailed information on these interfaces, refer to the EJB 2.1 Specification. This section also provides details about the WebLogic Server-specific timer-related interfaces.

EJB 2.1 Timer-related Programming Interfaces

EJB 2.1 interfaces you can use to program timers are described in the following table.

Table 4-2 EJB 2.1 Timer-related Programming Interfaces

Programming InterfaceDescription

javax.ejb.TimedObject

Implement for the enterprise bean class of a bean that will be registered with the timer service for timer callbacks. This interface has a single method, ejbTimeout.

EJBContext

Access the timer service using the getTimerService method.

javax.ejb.TimerService

Create new EJB timers or access existing EJB timers for the EJB.

javax.ejb.Timer

Access information about a particular EJB timer.

javax.ejb.TimerHandle

Define a serializable timer handle that can be persisted. Since timers are local objects, a TimerHandle must not be passed through a bean's remote interface or Web service interface.


For more information on EJB 2.1 timer-related programming interfaces, see the EJB 2.1 Specification.

WebLogic Server-specific Timer-related Programming Interfaces

WebLogic Server-specific interfaces you can use to program timers include:

  • weblogic.management.runtime.EJBTimerRuntimeMBean—provides runtime information and administrative functionality for timers from a particular EJBHome. The weblogic.management.runtime.EJBTimerRuntimeMBean interface is shown in Example 4-4.

Example 4-4 weblogic.management.runtime.EJBTimerRuntimeMBean Interface

public interface weblogic.management.runtime.EJBTimerRuntimeMBean {
  public int getTimeoutCount(); // get the number of successful timeout notifications that have been made
  public int getActiveTimerCount(); // get the number of active timers for this EJBHome
  public int getCancelledTimerCount(); // get the number of timers that have been cancelled for this EJBHome
  public int getDisabledTimerCount(); // get the number of timers temporarily disabled for this EJBHome
  public void activateDisabledTimers(); // activate any temporarily disabled timers
}
  • weblogic.ejb.WLTimerService interface—extends the javax.ejb.TimerService interface to allow users to specify WebLogic Server-specific configuration information for a timer. The weblogic.ejb.WLTimerService interface is shown in Example 4-5; for information on the javax.ejb.TimerService, see the EJB 2.1 Specification.


    Note:

    The weblogic.ejb.WLTimerService interface is not supported by the clustered EJB timer service, as described in Configuring Clustered EJB Timers.

Example 4-5 weblogic.ejb.WLTimerService Interface

public interface WLTimerService extends TimerService {
  public Timer createTimer(Date initial, long duration, Serializable info,
    WLTimerInfo wlTimerInfo)
    throws IllegalArgumentException, IllegalStateException, EJBException;
  public Timer createTimer(Date expiration, Serializable info,
    WLTimerInfo wlTimerInfo)
    throws IllegalArgumentException, IllegalStateException, EJBException;
  public Timer createTimer(long initial, long duration, Serializable info
    WLTimerInfo wlTimerInfo)
    throws IllegalArgumentException, IllegalStateException, EJBException;
  public Timer createTimer(long duration, Serializable info,
    WLTimerInfo wlTimerInfo)
    throws IllegalArgumentException, IllegalStateException, EJBException;
}
  • weblogic.ejb.WLTimerInfo interface—used in the weblogic.ejb.WLTimerService interface to pass WebLogic Server-specific configuration information for a timer. The weblogic.ejb.WLTimerInfo method is shown in Example 4-6.


    Note:

    The weblogic.ejb.WLTimerService interface is not supported by the clustered EJB timer service, as described in Configuring Clustered EJB Timers.

Example 4-6 weblogic.ejb.WLTimerInfo Interface

public final interface WLTimerInfo {
  public static int REMOVE_TIMER_ACTION  = 1;
  public static int DISABLE_TIMER_ACTION = 2;
  public static int SKIP_TIMEOUT_ACTION  = 3;
  /**
   * Sets the maximum number of retry attempts that will be
   * performed for this timer.  If all retry attempts
   * are unsuccesful, the timeout failure action will
   * be executed.
   */
  public void setMaxRetryAttempts(int retries);
  public int getMaxRetryAttempts();
  /**
   * Sets the number of milliseconds that should elapse
   * before any retry attempts are made.
   */
  public void setRetryDelay(long millis);
  public long getRetryDelay();
  /**
   * Sets the maximum number of timeouts that can occur
   * for this timer.  After the specified number of
   * timeouts have occurred successfully, the timer
   * will be removed.
   */
  public void setMaxTimeouts(int max);
  public int getMaxTimeouts();
/**
   * Sets the action the container will take when ejbTimeout
   * and all retry attempts fail.  The REMOVE_TIMER_ACTION,
   * DISABLE_TIMER_ACTION, and SKIP_TIMEOUT_ACTION fields
   * of this interface define the possible values.
   */
  public void setTimeoutFailureAction(int action);
  public int getTimeoutFailureAction();
}
  • weblogic.ejb.WLTimer interface—extends the javax.ejb.Timer interface to provide additional information about the current state of the timer. The weblogic.ejb.WLTimer interface is shown in Example 4-7.


    Note:

    The weblogic.ejb.WLTimerService interface is not supported by the clustered EJB timer service, as described in Configuring Clustered EJB Timers.

Example 4-7 weblogic.ejb.WLTimer Interface

public interface WLTimer extends Timer {
  public int getRetryAttemptCount();
  public int getMaximumRetryAttempts();
  public int getCompletedTimeoutCount();
}

Timer Deployment Descriptors

The following deployment descriptor elements pertain to timers.

Table 4-3 Timer Deployment Descriptors

ElementDescription

timer-descriptor

EJB timer object.

timer-implementation

Whether the EJB timer service is clustered or non-clustered. For information about the clustered EJB timer service, see Configuring Clustered EJB Timers.

persistent-store-logical-name

Name of a persistent store on the server's file system where WebLogic Server stores timer objects.


For more information on these elements, see weblogic-ejb-jar.xml Deployment Descriptor Reference.

Configuring Clustered EJB Timers


Note:

To review the advantages of using clustered EJB timers, see Clustered Versus Local EJB Timer Services.

To configure the clustering of EJB timers, perform the following steps:

  1. Ensure that you have configured the following:

    • A clustered domain. For more information, see "Setting up WebLogic Clusters" in Using Clusters for Oracle WebLogic Server.

    • Features of the Job Scheduler, including:

      • HA database, such as Oracle, DB2, Informix, MySQL, Sybase, or MSSQL.

      • JDBC data source that is mapped to the HA database using the <data-source-for-job-scheduler> element in the config.xml file.

      • Leasing service. By default, database leasing will be used and the JDBC data source defined by the <data-source-for-job-scheduler> element in the config.xml file will be used.

    For more information about configuring the Job Scheduler, see "The Timer and Work Manager API" in Timer and Work Manager API (CommonJ) Programmer's Guide for Oracle WebLogic Server.

  2. To enable the clustered EJB timer service, set the timer-implementation element in the weblogic-ejb-jar.xml deployment descriptor to Clustered:

    <timer-implementation>Clustered</timer-implementation>
    

    For more information, see timer-implementation.

Please note the following changes in the behavior of the clustered EJB timer service:

  • The weblogic.ejb.WLTimer* interfaces are not supported with clustered EJB timer services.

  • When creating a new clustered EJB timer using the createTimer() method, you may notice a delay in timeout execution during the initial setup of the timer.

  • The Job Scheduler provides an "at least once" execution guarantee. When a clustered EJB timer expires, the database is not updated until the timer listener callback method completes. If the server were to crash before the database is updated, the timer expiration would be executed twice.

  • Timer configuration options related to the actions to take in the event of failure are not valid for the clustered EJB timer service. These configuration options include: retry delay, maximum number of retry attempts, maximum number of timeouts, and timeout failure actions.

  • The Job Scheduler queries the database every 30 seconds to identify timers that are due to expire. Execution may be delayed for timers with an interval duration less than 30 seconds.

  • Only transactional timers will be retried in the event of failure.

  • Fixed rate scheduling of timer execution is not supported.

Declare Web Service References

This release of WebLogic Server complies with the EJB 2.1 requirements related to declaring and accessing external Web Services. Web Service references, declared in an EJB's deployment descriptor, maps a logical name for a Web Service to an actual Web Service interface, which allows you to refer to the Web Service using a logical name. The bean code then performs a JNDI lookup using the Web Service reference name.

For more information, see Getting Started With JAX-WS Web Services for Oracle WebLogic Server.

Compile Java Source

For a list of tools that support the compilation process, see Table 4-1.

For information on the compilation process, see Developing Applications for Oracle WebLogic Server.

Generate Deployment Descriptors

If you annotate your Bean class file with JDK 1.5 annotations, you can use EJBGen to generate the Remote and Home classes and the deployment descriptor files for an EJB application.

Oracle recommends that you use EJBGen to generate deployment descriptors. For more information, see Appendix E, "EJBGen Reference."

Edit Deployment Descriptors

Elements in ejb-jar.xml, weblogic-ejb-jar.xml, and for container-managed persistence entity beans, weblogic-cmp-jar.xml, control the run-time characteristics of your application.

If you need to modify a descriptor element, you can edit the descriptor file with any plain text editor. However, to avoid introducing errors, use a tool designed for XML editing. Descriptor elements that you can edit with the WebLogic Server Administration Console are listed in Table 4-1.

The following sections are a quick reference to WebLogic Server-specific deployment elements. Each section contains the elements related to a type of feature or behavior. The table in each section defines relevant elements in terms of the behavior it controls, the bean type it relates to (if bean type-specific), the parent element in weblogic-ejb-jar.xml that contains the element, and the behavior you can expect if you do not explicitly specify the element in weblogic-ejb-jar.xml.

For comprehensive documentation of the elements in each descriptor file, definitions, and sample usage, refer to:

Security Elements

This table lists the elements in weblogic-ejb-jar.xml related to security.

Table 4-4 Security Elements in weblogic-ejb-jar.xml

ElementDescriptionDefault

security-role-assignment


Maps security roles in ejb-jar.xml file to the names of security principals in WebLogic Server.

Required if ejb-jar.xml defines application roles.

none

security-permission


Additional Java security permission that is granted to this EJB.

none

run-as-principal-name


Security principal name to use as the run-as principal for a bean that has specified a security-identity run-as-role-name in ejb-jar.xml.

none

iiop-security-descriptor


Security options for beans that use the RMI-IIOP protocol.

none


Resource Mapping Elements

This table lists the elements in weblogic-ejb-jar.xml that map the names of beans or resources used in source code to their JNDI names in the deployment environment.

Table 4-5 Resource Mapping Elements in weblogic-ejb-jar.xml

ElementBean TypeDescriptionDefault

jndi-name


All

JNDI name of a resource or reference available in WebLogic Server.

Note: Assigning a JNDI name to a bean is not recommended. Global JNDI names generate heavy multicast traffic during clustered server startup. See Using EJB Links for the better practice.

none

local-jndi-name


All

JNDI name for a bean's local home. If a bean has both a remote and a local home, then it must have two JNDI names; one for each home.

none

concurrency-strategy


MDB

JNDI name of the JMS connection factory that the bean uses to create queues and topics.

weblogic.jms.Message.DrivenBeanConnectionFactory

destination-jndi-name


MDB

JNDI name that associates a message-driven bean with a queue or topic in the JNDI tree.

none

initial-context-factory


MDB

Initial context factory that the EJB container uses to create connection factories.

weblogic.jndi.WLInitial.Context.Factory

jms-client-id


MDB

Client ID for the message-driven bean associated with a durable subscriber topic.

Value of ejb-name

message-destination-descriptor


MDB

Maps a message destination reference in the ejb-jar.xml file to an actual message destination, such as a JMS Queue or Topic, in WebLogic Server.

n/a

provider-url


MDB

Specifies the URL provider to be used by the InitialContext.

t3://localhost:7001


Persistence Elements

This table lists elements in weblogic-ejb-jar.xml that specify how the state of a bean is persisted.

Table 4-6 Persistence Elements in weblogic-ejb-jar.xml

ElementBean TypeDescriptionDefault

type-identifier


Entity

Specifies EJB persistence type. WebLogic Server RDBMS-based persistence uses the identifier, WebLogic_CMP_RDBMS

n/a

type-storage


Entity

Defines path, relative to the top level of the EJB's JAR deployment file or deployment directory, of the file that stores data for this persistence type.

WebLogic Server RDBMS-based persistence generally uses an XML file named weblogic-cmp-jar.xml to store persistence data for a bean. This file is stored in the META-INF subdirectory of the JAR file.

n/a

type-version


Entity

Version of the persistence type specified by type-identifier. For WebLogic 2.0 CMP persistence, use the value 2.0.

For WebLogic 1.1 CMP persistence, use the value 1.1.

n/a

delay-updates-until-end-of-tx


Entity

If true, the EJB container attempts to delay writing updates to a bean's state to the database until the end of a transaction. However, the container still flushes updates to the database before executing an EJB finder or select query if the include-updates element (in the weblogic-query element of weblogic-cmp-jar.xml) for the query is true.

Applicable to both container-managed persistence and bean-managed persistence beans.

True

finders-load-bean


Entity

Causes beans returned by a finder or ejbSelect method to be loaded immediately into the cache before the method returns.

Note: Applicable to container-managed persistence beans only.

True

persistent-store-dir


Stateful Session

Directory where state of passivated stateful session bean instances is stored.

pstore

is-modified-method-name


Entity

The method called by the container to determine whether or not the bean has been modified and needs to have its changes written to the database.

Applies to bean-managed persistence or EJB 1.1 container-managed persistence beans.

If not specified, bean state is persisted after each method completes.


Clustering Elements

This table lists the elements in weblogic-ejb-jar.xml related to clustering. These elements control failover and load balancing behaviors for clustered beans in a WebLogic Server cluster.

Table 4-7 Clustering Elements in weblogic-ejb-jar.xml

ElementBean TypeDescriptionDefault

home-call-router-class-name


Stateful Session

Stateless Session

Entity

Custom class to be used for routing home method calls. This class must implement weblogic.rmi.extensions.CallRouter().

None

home-is-clusterable


Stateful Session

Stateless Session

Entity

Indicates whether the bean home can be clustered.

True

home-load-algorithm


Stateful Session

Stateless Session

Entity

Algorithm to use for load-balancing among replicas of the bean home.

Value of weblogic.cluster.defaultLoadAlgorithm

idempotent-methods


Stateless Session

Entity

Idempotent methods for a clustered EJB. An idempotent method can be repeated with no negative side-effects.

Methods of stateless session bean homes and read-only entity bean interfaces do not need to be explicitly identified—they are automatically set to be idempotent.

None

replication-type


Stateful Session

Indicates the replication used for stateful session beans in a cluster: in-memory or none.

none

stateless-bean-call-router-class-name


Stateless Session

Custom class to be used for routing bean method calls.

None

stateless-bean-is-clusterable


Stateless Session

Indicates that the bean is clusterable.

Use only for session beans whose session-type in ejb-jar.xml is Stateless.

True

stateless-bean-load-algorithm


Stateless Session

Algorithm to use for load-balancing among replicas of the bean.

Value of the property weblogic.cluster.defaultLoadAlgorithm

use-serverside-stubs


Stateless Session

Causes the bean home to use server-side stubs in the server context.

False


Data Consistency Elements

This table lists the elements in weblogic-ejb-jar.xml related to the consistency of the bean instance data and the database. These elements control behaviors such as how and when the database is updated to reflect the values in the bean instance is done.


Note:

For elements related to container-managed persistence, see Managing Entity Bean Pooling and Caching.

Table 4-8 Data Consistency Elements in weblogic-ejb-jar.xml

ElementBean TypeDescriptionDefault

concurrency-strategy


Entity

How concurrent access to an entity bean is managed.

Database

invalidation-target


Entity

The read-only entity bean to invalidate when this container-managed persistence entity bean is modified.

Note: Only applicable to EJB 2.x CMP beans.

None

delay-updates-until-end-of-tx


Entity

If true, the EJB container attempts to delay writing updates to a bean's state to the database until the end of a transaction. However, the container still flushes updates to the database before executing an EJB finder or select query if the include-updates element (in the weblogic-query element of weblogic-cmp-jar.xml) for the query is true.

Applicable to both container-managed persistence and bean-managed persistence beans.

True


Container-Managed Transactions Elements

Table 4-9 lists the elements in ejb-jar.xml related to container-managed transactions.

Table 4-9 Container-Managed Transaction Elements in ejb-jar.xml

ElementDescriptionDefault

transaction-type

Allowable values are Bean or Container.

None, EJB 2.x requires this attribute to be specified.

trans-attribute

Specifies how the container manages the transaction boundaries when delegating a method invocation to an enterprise bean's business method. Allowable values are:

  • NotSupported

    With the NotSupported value, when an entity bean runs in an unspecified transaction, if a transaction exists, the EJB container suspends the transaction; when an entity bean runs in an unspecified transaction, and no transaction exists, the EJB container takes no action.

  • Supports

    With the Supports value, when an entity bean runs in an unspecified transaction, if a transaction exists, the EJB container uses the current transaction; when an entity bean runs in an unspecified transaction, and no transaction exists, the EJB container takes no action.

  • Required

  • RequiresNew

  • Mandatory

  • Never

    With the Never value, when an entity bean runs in an unspecified transaction, if a transaction exists, the EJB container throws an exception; when an entity bean runs in an unspecified transaction, and no transaction exists, the EJB container takes no action.

Note: In in pre-9.0 releases of WebLogic Server, the EJB container would start a new transaction when no transaction existed and the value of trans-attribute was NotSupported, Supports, and Never. Set entity-always-uses-transaction in weblogic-ejb-jar.xml to True if you want the EJB container to behave as it did in pre-9.0 releases of WebLogic Server and create a new transaction.

Because clients do not provide a transaction context for calls to an MDB, MDBs that use container-managed transactions must have trans-attribute of Required.

If not specified, the EJB container issues a warning, and uses NotSupported for MDBs and Supports for other types of EJBs.

transaction-scope

This optional element specifies whether an enterprise bean requires distributed transactions for its methods or whether the local transaction optimization may be used.

Allowable values are Local and Distributed.

If not specified, the container assumes that distributed transactions must be used.


Table 4-10 lists the elements in weblogic-ejb-jar.xml related to container-managed transactions.

Table 4-10 Container-Managed Transaction Elements in weblogic-ejb-jar.xml

ElementDescriptionDefault

retry-methods-on-rollback


The methods for which you want the EJB container to automatically retry container-managed transactions that have rolled back.

Note: Regardless of the methods specified in this element, the EJB container does not retry any transactions that fail because of system exception-based errors.

None

transaction-isolation


The transaction isolation level used when method starts a transaction. The specified transaction level is not used if the method inherits an existing transaction.

The default of the underlying DBMS

trans-timeout-seconds


Maximum duration for a transaction.

None


Performance Elements

This table lists the elements in weblogic-ejb-jar.xml related to performance.

Table 4-11 Performance Elements in weblogic-ejb-jar.xml

ElementBean TypeDescriptionDefault

allow-concurrent-calls


Stateful Session

Whether multiple clients can simultaneously access a bean without triggering a Remote Exception.

The server throws a RemoteException when a stateful session bean instance is currently handling a method call and another (concurrent) method call arrives on the server.

False

cache-between-transactions


Entity

Causes the container to cache the persistent data of an entity bean between transactions.

False

cache-type


Stateful Session

Order in which stateful session beans are removed from the cache.

NRU

(not recently used)

clients-on-same-server


All

Indicates that all clients of the bean are collocated with the bean on the same server instance. This element is only used if the EJB has a global JNDI name; setting it to true prevents the JNDI name from being replicated.

A value of true can reduce cluster startup time in large clusters.

False

delay-updates-until-end-of-tx


Entity

If true, the EJB container attempts to delay writing updates to a bean's state to the database until the end of a transaction.

However, the container still flushes updates to the database before executing an EJB finder or select query if the include-updates element (in the weblogic-query element of weblogic-cmp-jar.xml) for the query is true.

Applicable to both container-managed persistence and bean-managed persistence beans.

True

dispatch-policy


All

Specifies the thread pool used to handle requests to the bean.

None

entity-cache-name


Entity

The application-level entity cache, which can cache instances of multiple entity beans that are part of the same application.

Note: Application level caches are declared in the weblogic-application.xml.

None

estimated-bean-size


Entity

Estimated average size, in bytes, of an entity bean instance.

None

finders-load-bean


Entity

Causes beans returned by a finder or ejbSelect method to be loaded immediately into the cache before the method returns.

Note: Applicable to container-managed persistence beans only.

True

idle-timeout-seconds


Entity

Number of seconds of inactivity after which a bean is passivated.

Note: This element is not currently used.

600

idle-timeout-seconds


Stateful Session

Number of seconds of inactivity after which a bean is passivated.

600

initial-beans-in-free-pool


Entity

Message-Driven

Stateless Session

Number of instances of an EJB instantiated by the container at startup.

0

is-modified-method-name


Entity

The method that changes the state of bean. Specifying this method causes WebLogic server to persist the bean state when the method completes.

Note: Applies to bean-managed persistence or EJB 1.1 container-managed persistence beans.

If not specified, bean state is persisted after each method completes.

jms-polling-interval-seconds


Message-driven

The number of seconds between attempts by the EJB container to reconnect to a JMS destination that has become unavailable.

10

max-beans-in-cache


Entity

Stateful Session

Maximum number of instances in the cache.

1000

max-beans-in-free-pool


Entity

Stateless Session

Message-Driven

Maximum number of instances in the free pool.

1000

read-timeout-seconds


Entity

The number of seconds between ejbLoad calls on a read-only entity bean. If read-timeout-seconds is 0, ejbLoad is only called when the bean is brought into the cache.

600


Network Communications Elements

This table lists the elements in weblogic-ejb-jar.xml related to network communications.

Table 4-12 Communications Elements in weblogic-ejb-jar.xml

ElementBean TypeDescriptionDefault

network-access-point


all

Assigns a custom network channel to an EJB.

n/a


Generate EJB Wrapper Classes, and Stub and Skeleton Files

Container classes include the internal representation of the EJB that WebLogic Server uses and the implementation of the external interfaces (home, local, and/or remote) that clients use. You can use Oracle Workshop for WebLogic Platform or appc to generate container classes.

Container classes are generated in according to the descriptor elements in weblogic-ejb-jar.xml. For example, if you specify clustering elements, appc creates cluster-aware classes that will be used for deployment. You can use appc directly from the command line by supplying the required options and arguments. See appc for more information.

The following figure shows the container classes added to the deployment unit when the EAR or JAR file is generated.

Figure 4-2 Generating EJB Container Classes

Description of Figure 4-2 follows

appc and Generated Class Name Collisions

Although infrequent, when you generate classes with appc, you may encounter a generated class name collision which could result in a ClassCastException and other undesirable behavior. This is because the names of the generated classes are based on three keys: the bean class name, the bean class package, and the ejb-name for the bean. This problem occurs when you use an EAR file that contains multiple JAR files and at least two of the JAR files contain an EJB with both the same bean class, package, or classname, and both of those EJBs have the same ejb-name in their respective JAR files. If you experience this problem, change the ejb-name of one of the beans to make it unique.

Because the ejb-name is one of the keys on which the file name is based and the ejb-name must be unique within a JAR file, this problem never occurs with two EJBs in the same JAR file. Also, because each EAR file has its own classloader, this problem never occurs with two EJBs in different EAR files.

Package

Oracle recommends that you package EJBs as part of an enterprise application. For more information, see "Deploying and Packaging from a Split Development Directory" in Developing Applications for Oracle WebLogic Server.

Packaging Considerations for EJBs with Clients in Other Applications

WebLogic Server supports the use of ejb-client.jar files for packaging the EJB classes that a programmatic client in a different application requires to access the EJB.

Specify the name of the client JAR in the ejb-client-jar element of the bean's ejb-jar.xml file. When you run the appc compiler, a JAR file with the classes required to access the EJB is generated.

Make the client JAR available to the remote client. For Web applications, put the ejb-client.jar in the /lib directory. For non-Web clients, include ejb-client.jar in the client's classpath.


Note:

WebLogic Server classloading behavior varies, depending on whether the client is stand-alone. Stand-alone clients with access to the ejb-client.jar can load the necessary classes over the network. However, for security reasons, programmatic clients running in a server instance cannot load classes over the network.

Deploy

Deploying an EJB enables WebLogic Server to serve the components of an EJB to clients. You can deploy an EJB using one of several procedures, depending on your environment and whether or not your EJB is in production.

For general instructions on deploying WebLogic Server applications and modules, including EJBs, see Deploying Applications to Oracle WebLogic Server. For EJB-specific deployment issues and procedures, see Chapter 8, "Deployment Guidelines for Enterprise JavaBeans" in this book — Programming WebLogic Enterprise JavaBeans for Oracle WebLogic Server.

Solving Problems During Development

The following sections describe WebLogic Server features that are useful for checking out and debugging deployed EJBs.

Adding Line Numbers to Class Files

If you compile your EJBs with appc, you can use the appc -lineNumbers command option to add line numbers to generated class files to aid in debugging. For information, see Appendix D, "appc Reference."

Monitoring Data

WebLogic Server collects a variety of data about the run-time operation of a deployed EJB. This data, which you can view in the Deployments node of the Administration Console, can be useful in determining if an EJB has completed desired processing steps. To access EJB run-time statistics, expand the Deployment node in the Administration Console, navigate to the JAR EAR that contains the bean, and select the Monitoring tab.

For information about the data available, see these pages in Oracle WebLogic Server Administration Console Help:

Creating Debug Messages

For instructions on how to create messages in your application to help you troubleshoot and solve bugs and problems, see Configuring Log Files and Filtering Log Messages for Oracle WebLogic Server.

WebLogic Server Tools for Developing EJBs

This section describes Oracle tools that support the EJB development process. For a comparison of the features available in each tool, see Table 4-14.

Oracle JDeveloper

Oracle JDeveloper is a full-featured Java IDE that can be used for end-to-end development of EJBs. For more information, see the Oracle JDeveloper online help. For information about installing JDeveloper, see Oracle Fusion Middleware Installation Guide for Oracle JDeveloper.

Oracle Enterprise Pack for Eclipse

Oracle Enterprise Eclipse (OEPE) provides a collection of plug-ins to the Eclipse IDE platform that facilitate development of WebLogic Web services. For more information, see the Eclipse IDE platform online help.

Administration Console

In the Administration Console, you can view, modify, and persist to the descriptor file within the EJB a number of deployment descriptor elements. Descriptors are modified in the Administration Server copy of the EJB as well as in any deployed copies of the EJB (after deployment). When you modify descriptors, changes are made to your (the user's) original copy of the EJB (prior to deployment).

However, updating these descriptor elements takes place dynamically at runtime without requiring that the EJB be redeployed. The descriptor element that you can change in the Administration Console are limited to only those that may be dynamically changed at runtime, as summarized in Table 4-13.

Table 4-13 Descriptor Elements Available from Administration Console

EJB TypeEditable Elements

Entity

Message-Driven

Stateless


Stateful



javac

The javac compiler provided with the Java SE JDK provides java compilation capabilities. For information on javac, see http://www.oracle.com/technetwork/java/index-jsp-142903.html#documentation.

EJBGen

EJBGen is an EJB 2.x code generator. You can annotate your bean class file with javadoc tags and then use EJBGen to generate the remote and home interface classes and the deployment descriptor files for an EJB application, reducing to one the number of EJB files you need to edit and maintain.

Oracle recommends that you use EJBGen to generate deployment descriptors; this is a Oracle best practice which allows for easier and simpler maintenance of EJBs. When you use EJBGen, you have to write and annotate only one bean class file, which simplifies writing, debugging, and maintenance. If you use Oracle Workshop for WebLogic Platform as a development environment, Workshop automatically inserts EJBGen tags for you.

For information on EJBGen, see Appendix E, "EJBGen Reference."

DDInit

DDInit is a utility for generating deployment descriptors for WebLogic Server applications. DDInit uses information from the class files to create deployment descriptor files.

See "DDInit" in Command Reference for Oracle WebLogic Server.

WebLogic Server Ant Utilities

WebLogic Server includes Ant utilities to create skeleton deployment descriptors.

The Ant task examines a directory containing an EJB and creates deployment descriptors based on the directory contents. Because the Ant utility does not have information about all desired configurations and mappings for your EJB, the skeleton deployment descriptors the utility creates are incomplete. After the utility creates the skeleton deployment descriptors, you can use a text editor or an XML editor to edit the deployment descriptors and complete the configuration of your EJB.

For more information, see "Deploying Applications Using wldeploy" in Developing Applications for Oracle WebLogic Server.

weblogic.Deployer

The weblogic.Deployer command-line tool is a Java-based deployment tool that provides a command line interface to the WebLogic Server deployment API. This tool was developed for administrators and developers who need to initiate deployment from the command line, a shell script, or any automated environment other than Java.

See "weblogic.Deployer Command-Line Reference" in Deploying Applications to Oracle WebLogic Server.

appc

The appc compiler generates and compiles the classes needed to deploy EJBs and JSPs to WebLogic Server. It validates the deployment descriptors for compliance with the current specifications at both the individual module level and the application level. The application-level checks include checks between the application-level deployment descriptors and the individual modules as well as validation checks across the modules.


Note:

The appc compiler replaces the deprecated ejbc utility. Therefore, Oracle recommends that you use appc instead of the deprecated ejbc.

See Appendix D, "appc Reference."

DDConverter

DDConverter is a command line tool that upgrades deployment descriptors from earlier releases of WebLogic Server. Oracle recommends that you always upgrade your deployment descriptors in order to take advantage of the features in the current Java EE specification and release of WebLogic Server.

You can use weblogic.DDConverter to upgrade your deployment descriptors. For information on using weblogic.DDConverter, see Developing Applications for Oracle WebLogic Server.


Note:

With this release of WebLogic Server, the EJB-specific DDConverter, weblogic.ejb20.utils.DDConverter, is deprecated. Instead, use the new application-level DDConverter, weblogic.DDConverter, to convert your application's deployment descriptors, including the EJB-specific deployment descriptors.

Comparison of EJB Tool Features

The following table lists Oracle tools for EJB development, and the features provided by each. (Yes indicates the tool contains the corresponding feature.

Table 4-14 EJB Tools and Features

EJB ToolGenerate Interfaces and Home InterfacesCompile Java CodeGenerate Deployment DescriptorsView and Edit Deployment DescriptorsDeploy

WebLogic Workshop

Yes

Yes

Yes

No

Yes

appc

No

Yes

No

No

No

javac

No

Yes

No

No

No

EJBGen

Yes

No

Yes

Yes

No

DDinit

No

No

Yes

No

No

Administration Console

No

No

No

Yes

Yes

Deployer

No

No

No

No

Yes

DDConverter

No

No

Yes

No

No


PK"ݥPK;wEOEBPS/entity.htm Entity EJBs

6 Entity EJBs

The sections that follow describe WebLogic Server value-added features for programming and using entity beans in applications, and provide associated design and development guidelines.

It is assumed that the reader is familiar with Java programming and entity bean features and capabilities. For an introduction to entity beans and how they are typically used in applications, see Entity EJBs Maintain Persistent Data and Entity Bean Features.

For a description of the overall bean development process, see Implementing Enterprise JavaBeans.

Managing Entity Bean Pooling and Caching

WebLogic Server provides these features to improve performance and throughput for entity EJBs:

  • Free pool—stores anonymous entity beans that are used for invoking finders, home methods, and creating entity beans.

  • Cache—contains instances that have an identity—a primary key, or are currently enlisted in a transaction (READY and ACTIVE entity EJB instances).

Figure 6-1 illustrates the life cycle of an entity bean instance. The sections that follow describe pooling and how the container populates and manages the free pool and the cache.

Figure 6-1 Entity Bean Life Cycle

Description of Figure 6-1 follows

Understanding Entity Pooling

If you specify a non-zero value for the initial-beans-in-free-pool element in weblogic-ejb-jar.xml, WebLogic Server populates the pool with the specified quantity of bean instances at startup.

The default value of initial-beans-in-free-pool is zero. Populating the free pool at startup improves initial response time for the EJB, because initial requests for the bean can be satisfied without generating a new instance. In this release of WebLogic Server, administrators can also initialize pools on demand via the Administration Console. When a pool is initialized, it is reset to the state it was in immediately after the EJB was deployed. For information, see "Initialize the idle bean cache and pool of an EJB" in Oracle WebLogic Server Administration Console Help.

An attempt to obtain an entity bean instance from the free pool will always succeed, even if the pool is empty. If the pool is empty, a new bean instance is be created and returned.

Pooled beans are anonymous instances, and are used for finders and home methods. The maximum number of instances the pool can contain is specified by the max-beans-in-free-pool element, in weblogic-ejb-jar.xml which set to 1,000 by default.

You can configure WebLogic Server to remove entity beans that have remained in the pool unused for a period of time specified in idle-timeout-seconds element in the pool element. When beans have been in the pool unused for the amount of time you specify in idle-timeout-seconds, they are removed from the pool until the number of beans in the pool reaches the number specified in initial-beans-in-free-pool; the number of beans in the pool will never fall below the number specified in initial-beans-in-free-pool.

Understanding Entity Caching

When a business method is called on a bean, the container obtains an instance from the pool, calls ejbActivate, and the instance services the method call.

A READY instance is in the cache, has an identity—an associated primary key, but is not currently enlisted in a transaction. WebLogic maintains READY entity EJB instances in least-recently-used (LRU) order.

An ACTIVE instance is currently enlisted in a transaction. After completing the transaction, the instance becomes READY, and remains in cache until space is needed for other beans.

The Current Beans in Cache field in the Administration Console Monitoring tab displays the count of READY and ACTIVE beans. Additionally, in this release of WebLogic Server, Administrators can initialize caches on demand via the Administration Console. When a cache is initialized, it is reset to the state it was in immediately after the EJB was deployed. For information, see "Initialize the idle bean cache and pool of an EJB" in Oracle WebLogic Server Administration Console Help.

The effect of the max-beans-in-cache element, and the quantity of instances with the same primary key allowed in the cache vary by concurrency strategy. Table 6-0 lists, for each concurrency strategy, how the value of the max-beans-in-cache element in weblogic-ejb-jar.xml limits the number of entity bean instances in the cache, and how many entity bean instances with the same primary key are allowed in the cache.

Table 6-1 Entity EJB Caching Behavior by Concurrency Type

Concurrency OptionWhat is the effect of max-beans-in-cache on the number of bean instances in the cache?How many instances with same primary key can exist in cache simultaneously?

Exclusive

max-beans-in-cache = number of ACTIVE bean + number of READY instances.

one

Database

The cache can contain up to max-beans-in-cache ACTIVE bean instances and up to max-beans-in-cache READY bean instances.

multiple

ReadOnly

max-beans-in-cache = number of ACTIVE bean + number of READY instances.

one


READY entity EJB instances are removed from the cache when the space is needed for other beans. When a READY instance is removed from cache, ejbPassivate is called on the bean, and the container will try to put it back into the free pool.

You can configure WebLogic Server to periodically remove entity instances from cache when they have been idle—not participated in a transaction—for a period of time specified in idle-timeout-seconds. For a dedicated cache, the fixed periodicity of the cleaning task is equal to the value of idle-timeout-seconds. For an application level cache, multiple types of entity beans may share the cache each of which is allowed to have its own value of idle-timeout-seconds. In this case, the fixed periodicity of the cleaning task is equal to MIN(Set of idle-timeout-seconds for all beans in cache), and the cleaning task may run with a variable periodicity.

When the container tries to return an instance to the free pool and the pool already contains max-beans-in-free-pool instances, the instance is discarded.

ACTIVE entity EJB instances will not be removed from cache until the transaction they are participating in commits or rolls back, at which point they will become READY, and hence eligible for removal from the cache.

Understanding Passivation of Entity Beans

Entity beans that are involved in transactions can be passivated when necessary in order to attempt to prevent a CacheFullException when an attempt is made to insert an entity bean into a cache that is full. Passivation is handled automatically by the EJB container and you do not need to change the way you program EJBs in order to take advantage of this feature. However, you can optionally program your EJBs to communicate to the cache that they are done performing all operations in the current transaction. The cache can then make use of this information when evaluating beans for the possibility of passivation.

To optionally program EJBs to notify their cache that they are done performing operations in the current transaction, you can use the operationsComplete Java API as follows:

weblogic.ejb.interfaces.EJBLocalObject
public.void.operationsComplete()
weblogic.ejb.EJBObject
public.void.operationsComplete()

Understanding ejbLoad() and ejbStore() Behavior

This section describes how and when the persistent data for a CMP 2.1 entity bean is loaded to cache and written back to persistent storage.

  • findXXX()—By default, calling a finder method on a CMP bean results in immediate load of the bean's persistent data to cache. This behavior is controlled by the finders-load-bean element in the persistence element of weblogic-ejb-jar.xml.

  • ejbLoad()—For CMP 2.1 entity beans, ejbLoad() causes a "lazy" load of a bean's persistent data to the entity cache when the next getXXX() for the bean's data is called. That is, when a transaction is initiated for a CMP 2.0 entity bean instance, WebLogic Server reads the bean's data from the entity cache, rather than the database, unless ejbLoad() has been called since the bean was last loaded to cache.

    By default, WebLogic Server calls ejbLoad() each time a new transaction is initiated for the entity bean.


    Note:

    When used with CMP 1.1 entity beans and entity beans that use bean-managed persistence, ejbLoad() does not perform the lazy load—for these bean types, the bean's persistent data is loaded to cache during the ejbLoad().

  • ejbStore()—WebLogic Server writes the persistent fields of an entity EJB to the database using calls to ejbStore().

    By default, WebLogic Server calls ejbStore() when the transaction commits.

Controlling the Behavior of ejbLoad() and ejbStore()

For applications in which multiple clients can currently access and modify a bean's underlying data, the default behavior of ejbLoad() and ejbStore() described in Understanding ejbLoad() and ejbStore() Behavior ensures database integrity by:

  • Ensuring that each new transaction uses the latest version of the EJB's persistent data, and

  • Updating the database upon transaction commitment.

However, depending on your requirements, you may prefer to call ejbLoad() and ejbStore() either more or less frequently. For instance, you might want to limit calls that access the database for performance reasons. If your application does not allow multiple transactions to concurrently access the EJB—for example, if the bean uses Exclusive concurrency—loading the data at the beginning of each transaction is unnecessary. Given that no other clients or systems update the EJB's underlying data, the cached EJB data is always up-to-date, and calling ejbLoad() results in extra overhead. In such cases, you can safely reduce calls to ejbLoad(), as described in Limiting Database Reads with cache-between-transactions.

Alternatively, you might want to deviate from the standard ejbStore() behavior, by calling it before a transaction commits, in order to access and use intermediate transaction results. For instructions, see Updating the Database Before Transaction Ends.

Disabling Cache Flushing

According to the EJB specification, updates made by a transaction must be reflected in the results of query-finders and ejbSelects issued during the transaction. This requirement can slow performance. If you prefer not to flush the cache before the query is executed, you can change the value of the include-updates element in weblogic-cmp-jar.xml from its default value of True to False.

The decision to disable cache flushing depends on whether performance is more important than seeing the most current data. Setting include-updates to False provides the best performance but updates of the current transaction are not reflected in the query. If include-updates is True the container flushes all changes for the transactions to the database before executing the new query.

You can safely turn cache flushing off if your transactions do not re-query modified data—a common scenario—and get the best performance.

Configuring Application-Level Caching

Application-level caching—also known as "combined caching"—allows multiple entity beans that are part of the same Java EE enterprise application to share a single runtime cache. There are no restrictions on the number of different entity beans that may reference an individual cache.

Application-level caching offers the following advantages:

  • Reduces the number of entity bean caches, and hence the effort to configure the cache.

  • Better utilization of memory and heap space, because of reduced fragmentation. For example, if a particular EJB home experiences a burst of activity, it can make use of all memory available to the combined cache, while other EJBs that use the cache are paged out. If two EJBs use different caches, when one bean's cache becomes full, the container cannot page out EJBs in the other bean's cache, resulting in wasted memory.

  • Simplifies management; combined caching enables a system administrator to tune a single cache, instead of many caches.

  • Provides better scalability

Application-level caching is not the best choice, however, for applications that experience high throughput. Because one thread of control exists per cache at a time, high throughput can create a bottleneck situation as tasks compete for control of the thread.

To configure an application-level cache:

  1. Verify that the weblogic-application.xml file is located in the META-INF directory of the EAR file.

  2. Define the application-level cache in the entity-cache element of weblogic-application.xml. For a definition of this element and the child elements it contains, see "entity-cache" in "Enterprise Application Deployment Descriptor Elements" in Developing Applications for Oracle WebLogic Server.

  3. Reference the application-level cache in the entity-cache-ref element of the entity-descriptor element in weblogic-ejb-jar.xml.

    Note that:

    • entity-cache-name should be the name of the application-level cache, as specified in weblogic-application.xml.

    • The concurrency-strategy you specify for the bean must be compatible with the caching-strategy specified in weblogic-application.xml. A read-only entity can only use a multiversion application-level cache. For more information, see "caching-strategy" in "Enterprise Application Deployment Descriptor Elements" in Deploying Applications to Oracle WebLogic Server.

The weblogic-application.xml deployment descriptor is documented in "Enterprise Application Deployment Descriptor Elements" in Deploying Applications to Oracle WebLogic Server.

Using Primary Keys

Every entity EJB must have a primary key that uniquely identifies an entity bean within its home. Each entity bean instance can define a different class for its primary key; multiple entity beans can use the same primary key class, as appropriate.

If two entity bean instances have the same home and the same primary key, they are considered identical. A client can invoke the getPrimaryKey() method on the reference to an entity bean instance's remote interface to determine the instance's identity within its home.

The instance identity associated with a reference does not change during the lifetime of the reference. Therefore, the getPrimaryKey() method always returns the same value when called on the same entity object reference. A client that knows the primary key of an entity object can obtain a reference to the entity object by invoking the findByPrimaryKey(key) method on the bean's home interface.

Specifying Primary Keys and Primary Key Classes

You can map a primary key to one or multiple fields:

  • Mapping a Primary Key to a Single CMP Field

    In the entity bean class, you can have a primary key that maps to a single CMP field. CMP fields must be specified in both ejb-jar.xml and weblogic-cmp-jar.xml. In both descriptor files, CMP fields are specified in the cmp-field element. For simple primary keys, also specify the primary key in the primkey-field element in the ejb-jar.xml. In addition, specify the primary key field's class in the prim-key-class element in ejb-jar.xml.

  • Wrapping One or More CMP Fields in a Primary Key Class

    You can define your own primary key class that maps to single or multiple CMP fields. The primary key class must be public, and have a public constructor with no parameters. Specify the name of the primary key class in the prim-key-class element in ejb-jar.xml. All fields in the primary key class must be public, and must have the same names as the corresponding cmp-fields in ejb-jar.xml and weblogic-ejb-jar.xml. For compound primary keys, which map to multiple CMP fields, do not specify primkey-field in ejb-jar.xml.

  • Anonymous Primary Key Class

    If your entity EJB uses an anonymous primary key class, you must subclass the EJB and add a cmp-field of type java.lang.Integer to the subclass. Enable automatic primary key generation for the field so that the container fills in field values automatically, and map the field to a database column in the weblogic-cmp-jar.xml deployment descriptor.

    Finally, update the ejb-jar.xml file to specify the EJB subclass, rather than the original EJB class, and deploy the bean to WebLogic Server.


    Note:

    If you use the original EJB (instead of the subclass) with an anonymous primary key class, WebLogic Server displays the following error message during deployment:

    In EJB ejb_name, an 'Unknown Primary Key Class' ( <prim-key-class> == java.lang.Object ) MUST be specified at Deployment time (as something other than java.lang.Object).


Guidelines for Primary Keys

Follow these suggestions when using primary keys with WebLogic Server:

  • Do not construct a new primary key class with an ejbCreate. Instead, allow the container to create the primary key class internally, as described in Automatically Generating Primary Keys.

  • In an application that manages its own primary key values, for a simple primary key—one composed of a single atomic value such as a String or an Integer—make the primary key class a container-managed field. Set the value of the primary key cmp-field using the setXXX method within the ejbCreate method.

  • Do not use a cmp-field of the type BigDecimal as a primary key field for CMP beans. The boolean BigDecimal.equals (object x) method considers two BigDecimal equal only if they are equal in value and scale. This is because there are differences in precision between the Java language and different databases. For example, the method does not consider 7.1 and 7.10 to be equal. Consequently, this method will most likely return False or cause the CMP bean to fail.

    If you need to use BigDecimal as the primary key, you should:

    1. Implement a primary key class.

    2. In the primary key class, implement the boolean equal (Object x) method.

    3. In the equal method, use boolean BigDecimal.compareTo(BigDecimal val).

  • If you are mapping a database column to a cmp-field and a cmr-field concurrently and the cmp-field is a primary key field, set the value when the ejbCreate() method is invoked by using the setXXX method for the cmp-field. In this case, the cmr-field is initialized automatically, and the setXXX method for the cmr-field cannot be used. Conversely, if the cmp-field is not a primary key field, the cmp-field is read-only. The column is updated using the cmr-field, and the cmp-field provides a read-only view of the foreign key.

Automatically Generating Primary Keys

WebLogic Server supports the automatic primary key generation feature for CMP entity beans. This feature is supported for simple (non-compound) primary keys only.

WebLogic Server supports two methods of automatic primary key generation:

  • Native database primary key generation—The database generates the primary key. To enable this feature, specify the database and a generator name in the <automatic-key-generation> element of weblogic-cmp-jar.xml. Based on the values you configure, the container generates code that obtains the primary key from the database. This feature is supported for Oracle and Microsoft SQL Server databases only. In addition, see the instructions in Declaring Primary Key Field Type.

  • Primary keys generated from a SEQUENCE table.

Whichever method of generated primary keys you use, see the instructions in Declaring Primary Key Field Type.

Specifying Automatic Key Generation for Oracle Databases

Generated primary key support for Oracle databases uses a SEQUENCE entity in the Oracle database to generate unique primary keys. The Oracle database SEQUENCE is called when a new number is needed. Specify automatic key generation in the automatic-key-generation element in weblogic-cmp-jar.xml. Specify the name of the Oracle database SEQUENCE in the generator-nam element. If the Oracle database SEQUENCE was created with a SEQUENCE INCREMENT, specify a key-cache-size. The value of key-cache-size must match the value of the Oracle database SEQUENCE INCREMENT. If these two values are different, duplicate keys can result.

When using the Oracle database SEQUENCE object for generating primary keys:

  • Do not set the generator-type to USER_DESIGNATED_TABLE with Oracle. Doing so sets the TX ISOLATION LEVEL to SERIALIZABLE, which can cause the following exception:

    javax.ejb.EJBException: nested exception is: java.sql.SQLException: Automatic
    Key Generation Error: attempted to UPDATE or QUERY NAMED SEQUENCE TABLE
    NamedSequenceTable, but encountered SQLException java.sql.SQLException:
    ORA-08177: can't serialize access for this transaction. 
    

    Instead, use the AutoKey option with Oracle databases.

  • In this release, WebLogic Server does not support Oracle database's synonym feature for the SEQUENCE schema object. If you migrate an application that uses synonyms for SEQUENCEs from a release prior to WebLogic Server 8.1 to this release, the following errors result:

    [EJB:011066]During EJB deployment, error(s) were encountered while setting up The ORACLE SEQUENCE named 'XXX' with INCREMENT value '1'
    [EJB:011064]The ORACLE SEQUENCE named 'XXX' with INCREMENT '1' was not found in the database' 
    

Specifying Automatic Key Generation for Microsoft SQL Server

Generated primary key support for Microsoft SQL Server databases uses SQL Server's IDENTITY column. When the bean is created and a new row is inserted in the database table, SQL Server automatically inserts the next primary key value into the column that was specified as an IDENTITY column.


Note:

For instructions on creating a SQL Server table that contains an IDENTITY column, see Microsoft documentation.

Once the IDENTITY column is created in the table, specify automatic key generation in weblogic-cmp-jar.xml as shown below.

<automatic-key-generation>
     <generator-type>SQLServer</generator-type>
</automatic-key-generation>

Generating Primary Keys with a Named Sequence Table

A sequence table is a database-neutral way to generate primary keys. The sequence table holds a monotonically increasing integer sequence value that is used as the primary key value in bean instances as they are created.

Create a table named SEQUENCE to hold the current primary key value. The table consists of a single row with a single column, as defined by the following statement:

CREATE table_name (SEQUENCE int)
INSERT into table_name VALUES (0)

To use this feature, make sure that the underlying database supports a transaction isolation level of Serializable. The Serializable value indicates that simultaneously executing a transaction multiple times has the same effect as executing the transaction multiple times in a serial fashion. This is important in a WebLogic Server cluster, in which multiple servers instances access the sequence table concurrently. See your database documentation to determine the isolation levels it supports.

Specify automatic key generation in the weblogic-cmp-jar.xml file, as shown below. In addition, see the instructions in Declaring Primary Key Field Type.

<automatic-key-generation>
    <generator-type>NamedSequenceTable</generator-type>
    MY_SEQUENCE_TABLE_NAME</generator-name>
    <key-cache-size>100</key-cache-size>
</automatic-key-generation>

Specify the name of the sequence table in the generator-name element.

Specify the size of the key cache— how many keys the container will fetch in a single DBMS call—in the key-cache-size element. Oracle recommends a key-cache-size greater than one. This setting reduces the number of calls to the database to fetch the next key value.

Oracle recommends that you define one NAMED SEQUENCE table per bean type. Beans of different types should not share a common NAMED SEQUENCE table. This reduces contention for the key table.

Declaring Primary Key Field Type

For both native DBMS primary key generation, or key generation using a named sequence table, in the abstract get and set methods of the associated entity bean, declare the primary field type to be either:

  • java.lang.Integer

  • java.lang.Long

In weblogic-cmp-jar.xml, set the key-cache-size element to specify how many primary key values in the sequence should be fetched from the database at a time. For example, setting key_cache_size to 10 results in one database access for every 10 beans created, to update the sequence. The default value of key_cache_size is 1. Oracle recommends that you set key_cache_size to a value greater than one, to minimize database accesses and to improve performance.

Support for Oracle Database SEQUENCE

WebLogic Server can automatically create an Oracle database SEQUENCE—a number generator that generates a unique integer each time it is called.

An Oracle database SEQUENCE can use a specified "increment value", which is the value by which the integer is incremented on each subsequent generation. For example, if a SEQUENCE generates the integer 24 and the increment value is 10, then the next integer the SEQUENCE generates will be 34.

String-Valued CMP Field Trimming

In this release of WebLogic Server, by default, the EJB container trims string-valued CMP fields of their trailing spaces when they are retrieved from a database. All string-valued CMP fields are also trimmed of their trailing spaces in their set method.

Benefits of String Trimming

Untrimmed primary key fields can cause comparison operators to fail and can result in non-portable behavior. Automatic string trimming is beneficial because it causes a string retrieved from a database to be identical to the string that was inserted into the database. For instance, suppose:

  • a primary key field is mapped to the char(10) datatype in database

  • you insert the value "smith" into the database column

  • since "smith" is five characters in length and the char datatype is a fixed-length—of ten characters, in this case—the database pads the value by appending five blank spaces, resulting in "smith " being inserted into the database

  • you issue a SELECT statement to retrieve "smith" from the database, only, due to the database-appended characters, "smith " is retrieved

A comparison of the retrieved "smith " value with the original "smith" string would fail unless the retrieved value was first trimmed of its trailing spaces. With this release of WebLogic Server, the trailing spaces are trimmed automatically and, therefore, the comparison would not fail.

Disabling String Trimming

Automatic string trimming is enabled by default in this release. When you use DDConverter to convert deployment descriptors from prior releases of WebLogic Server, DDConverter automatically disables string trimming in the new deployment descriptors it creates.

If you want to disable string trimming for deployment descriptors that are newly created in this release of WebLogic Server, you can set disable-string-trimming in weblogic-cmp-jar.xml to True. For more information on the disable-string-trimming element, see disable-string-trimming.

Configuring Entity EJBs for Database Operations

The following sections provide instructions for mapping entity EJBs to database tables and controlling database access behaviors.

Configuring Table Mapping

A CMP bean can be mapped to one or more database tables. When a CMP bean is mapped to multiple tables, each table contains a row that corresponds to a particular bean instance. So, each table to which a bean maps will have the same number of rows at any point in time, and contain the same set of homogeneous primary key values. Consequently, each table must have the same number of primary key columns, and corresponding primary key columns in different tables must have the same type, though they may have different names. Tables that map to the same bean must not have referential integrity constraints declared between their primary keys. If they do, removal of a bean instance can result in a runtime error.

You map the cmp-fields of a bean to the columns of a table using the table-map element in weblogic-cmp-jar.xml, specifying one table-map element for each database table to which the bean maps. Each table-map element maps the primary key column(s) of the table to the primary key field(s) of the bean. Non-primary key fields may only be mapped to a single table.

Example 6-1 and Example 6-2 contain table-map elements for a bean that maps to a single and a bean that maps to multiple tables, respectively.

Example 6-1 Mapping a CMP Entity to One Database Table

<table-map>
    <table-name>TableName</table-name>
    <field-map>
        <cmp-field>name</cmp-field>
        <dbms-column>name_in_tablename</dbms-column>
    </field-map>
    <field-map>
        <cmp-field>street_address</cmp-field>
        <dbms-column>street_address_in_tablename
        </dbms_column>
    </field-map>
    <field-map>
        <cmp-field>phone</cmp-field>
        <dbms-column>phone_in_tablename</dbms-column>
    </field-map>

Example 6-2 Mapping a CMP Entity to Two DBMS Tables

<table-map>
    <table-name>TableName_1</table-name>
        <field-map>
        <!--Note 'name'is the primary key field of this EJB -->
            <cmp-field>name</cmp-field>
            <dbms-column>name_in_tablename_1</dbms-column>
        </field-map>
        <field-map>
            <cmp-field>street_address</cmp-field>
            <dbms-column>street_address_in_tablename_1</dbms-column>
        </field-map>
</table-map>
<table-map>
    <table-name>TableName_2</table-name>
         <field-map>
         <!--Note 'name'is the primary key field of this EJB -->
             <cmp-field>name</cmp-field>
             <dbms-column>name_in_tablename_2</dbms-column>
        </field-map>
        <field-map>
             <cmp-field>phone</cmp-field>
             <dbms-column>phone_in_tablename_2</dbms-column>
         </field-map>
</table-map>

Automatic Table Creation (Development Only)

To make iterative development easier, the WebLogic Server EJB container can be configured to automatically change the underlying table schema as entity beans change, ensuring that tables always reflect the most recent object relationship mapping.


Note:

This feature is disabled when a server instance is running in production mode, as a production environment may require the use of more precise table schema definitions. To ensure that the container only changes tables it created, container-created tables include an extra column, called wls_temp.

The syntax of table creation statements (DDL) varies from database to database, so table creation may fail on databases that are not fully supported. If this occurs, create the tables manually.

Table 6-2 Controlling Automatic Table Creation Behavior With <create-default-dbms-tables>

Setting <create-default-dbms-tables> to this value...Results in this behavior...

Disabled

The EJB container takes no action when underlying table schema changes. This is the default value.

CreateOnly

For each CMP bean in the JAR, if there is no table in the database for the bean, the container attempts to create the table based on information found in the deployment descriptor, including join tables, sequence tables, and Oracle database sequences. If table creation fails, a Table Not Found error is thrown, and the user must create the table manually.

DropAndCreate

For each CMP bean in the JAR:

  • if table columns have not changed, no action is taken, and the existing data is preserved.

  • if the columns have changed, then the container drops and recreates the table and all table data is lost.

Note: You must ensure that the column type and cmp-field types are compatible. The EJB container does not attempt to ensure the column type and cmp-field types are compatible.

DropAndCreate

Always

For each CMP bean listed in the JAR, the container drops and creates the table whether or not columns have changed.

AlterOrCreate

For each CMP bean in the JAR:

  • if the table exists, the container attempts to alter the table schema using the ALTER TABLE SQL command and the container saves the data.

  • if the table does not exist, the container creates the table during deployment.

Note: Do not use AlterOrCreate if a new column is specified as a primary key or a column with null values is specified as the new primary key column. Due to database limitations, use DropAndCreate instead.



Note:

Sequence tables, join tables, and Oracle database SEQUENCEs are supported.

Enable this feature using the create-default-dbms-table element in weblogic-cmp-jar.xml. The behavior of this feature varies according to the value of the element, as described in the following table. The EJB container actions described in the table occur during deployment.

Delaying Database Inserts

Because of timing issues that may occur when creating a CMP bean, WebLogic Server enables you to specify at what point during the bean creation process the bean is inserted into the database.

Why Delay Database Inserts?

You cannot set a cmr-field until the primary key value for the bean—which is set when ejbPostCreate is called—is available. Hence, you cannot set a cmr-field until ejbPostCreate. This factor in combination with other conditions can lead to these problems:

  • Problem 1: Non-null foreign key constraint

    If a database row is inserted after ejbCreate (that is, before ejbPostCreate), then the foreign key is given a null value. This is because foreign key columns are set when cmr-fields are set.

    Solution: Set delay-insert-until in weblogic-cmp-jar.xml to ejbCreate, which causes the insert to be done immediately after the ejbCreate, and set the relationship during ejbPostCreate.

  • Problem 2: Creating beans during ejbPostCreate

    When a related bean is created, the database insert for that bean happens before the create call finishes. If the database row for the related bean contains a foreign key that refers to the current bean and the foreign key has a referential integrity constraint defined, the insert will fail if the current bean's database row has not been inserted yet.

    Solution: Set delay-insert-until to ejbCreate so that the row for the current bean exists during the ejbPostCreate.


    Note:

    In a one-to-one relationship, if the parent bean's primary key is embedded in the child bean's CMR field, when the EJB container creates the beans, it will not check if the parent bean has children, for performance reasons. To avoid a duplicationKeyException database exception, you must set the foreign key constraint on the child table in the database.

  • Problem 3: Both Problem 1 and Problem 2 exist

    Solution: Do not create related beans during ejbPostCreate. Create the current bean and after the creation is finished, create the related beans and set up relationships.

    Oracle recommends that applications always do this. Applications should never create related beans during creation of another bean.

Configuring Delayed Database Inserts

You can delay database inserts until the end of the ejbCreate method or ejbPostCreate method, using the delay-database-insert-until element in weblogic-cmp-jar.xml. To batch, order, and perform updates at the end of the transaction, set both enable-batch-operations and order-database-operations in weblogic-cmp-jar.xml to "True".

If you choose to delay database updates for a transaction that updates related beans, you must define the relationship between the beans in the weblogic-rdbms-relation of weblogic-cmp-jar.xml. Otherwise, database constraint errors may result when the EJB container attempts to perform the updates.

Limiting Database Reads with cache-between-transactions

As described in Understanding ejbLoad() and ejbStore() Behavior, by default, WebLogic Server calls ejbLoad() each time a transaction is initiated for an entity bean.

You can configure WebLogic Server to call ejbLoad() only when a client first references the bean or when a transaction is rolled back. This behavior is referred to as long-term caching. You enable long-term caching by setting the cache-between-transactions element in weblogic-ejb-jar.xml to true.

Long-term caching is allowed only if the concurrency-strategy for a bean is Exclusive, ReadOnly, or Optimistic. When long-term caching is configured for a:

  • ReadOnly bean, WebLogic Server ignores the value of the cache-between-transactions. WebLogic Server always performs long-term caching of read-only data, regardless of the value of cache-between-transactions.

  • Exclusive bean, the EJB container must have exclusive update access to the underlying data: the data must not be updated by another application outside of the EJB container.


    Note:

    If a bean with Exclusive concurrency is deployed in a cluster long-term caching is automatically disabled because any server instance in the cluster may update the bean data. This would make caching between transactions impossible.

  • Optimistic bean, the EJB container reuses cached data for each transaction after the client first references the bean, but ensures that updates are transactionally consistent by checking for optimistic conflicts at the end of each transaction.


    Note:

    In a cluster, when a bean with Optimistic concurrency is updated, notifications are broadcast to other cluster members to prevent optimistic conflicts.

Table 6-3 lists the allowable values for the cache-between-transactions element by entity bean type and concurrency strategy.

Table 6-3 Permitted cache-between-transactions values, by Concurrency Strategy and Entity Type

Concurrency StrategyBMP EntityCMP 2.0 BeanCMP 1.1 Entity

Database

False

False

False

Exclusive

True or False

True or False

True or False

Optimistic

Not applicable. Optimistic concurrency is not available for BMP beans.

True or False

Not applicable. Optimistic concurrency is not available for CMP 1.1 beans.


Updating the Database Before Transaction Ends

As described in Understanding ejbLoad() and ejbStore() Behavior, by default, WebLogic Server calls ejbStore() only when the transaction commits.

To make intermediate results of uncommitted transactions available to other database users, set delay-updates-until-end-of-tx in the persistence element of weblogic-ejb-jar.xml to False—this causes WebLogic Server to call ejbStore() after each method call.


Note:

While setting delay-updates-until-end-of-tx to false results in database updates after each method call, the updates are not committed until the end of the transaction.

Dynamic Queries

Dynamic queries allow you to construct and execute EJB-QL or SQL queries programmatically in your application code.

Using dynamic queries provides the following benefits:

  • The ability to create and execute new queries without having to update and deploy an EJB.

  • The ability to reduce the size of the EJB's deployment descriptor file. This is because finder queries can be dynamically created instead of statically defined in the deployment descriptors.

Enabling Dynamic Queries

To enable dynamic queries:

  1. Set the enable-dynamic-queries element in the EJB's weblogic-ejb-jar.xml to True:

    <enable-dynamic-queries>True</enable-dynamic-queries>
    
  2. Set standard method permissions to control access to dynamic queries by specifying the method-permission element in the ejb-jar.xml deployment descriptor file.

    Setting method-permission for the createQuery() method of the weblogic.ejb.QueryHome interface controls access to the weblogic.ejb.Query object necessary to execute the dynamic queries.

    If you specify method-permission for the createQuery() method, the method-permission settings apply to the execute and find methods of the Query class.

Executing Dynamic Queries

The following code sample demonstrates how to execute a dynamic query.

InitialContext ic=new InitialContext();
FooHome fh=(FooHome)ic.lookup("fooHome");
QueryHome qh=(QueryHome)fh;
String ejbql="SELECT OBJECT(e)FROM EmployeeBean e WHERE e.name='rob'"
Query query=qh.createQuery();
query.setMaxElements(10)
Collection results=query.find(ejbql);

Enabling BLOB and CLOB Column Support for Oracle or DB2 Databases

WebLogic Server supports Oracle and DB2 databases Binary Large Object (BLOB) and Character Large Object (CLOB) DBMS columns for CMP entity beans.

WebLogic Server maps BLOBs to a cmp-field that has a byte array or serializable type. At this time, no support is available for mapping char arrays to a CLOB column.

To enable BLOB/CLOB support:

  1. In the bean class, declare the variable.

  2. Edit the XML by declaring the dbms-default-value and dbms-column-type deployment descriptors in the weblogic-cmp-jar.xml file.

  3. Create the BLOB or CLOB in the Oracle or DB2 database.

Specifying a BLOB Column Using the Deployment Descriptor

The following XML code shows how to specify a BLOB object using the dbms-column-type element in weblogic-cmp-jar-xml file.

<field-map>
    <cmp-field>photo</cmp-field>
    <dbms-column>PICTURE</dbms-column>
    <dbms-column-type>Blob</dbms-column-type>
    <dbms-default-value>DB2</dbms-default-value>
</field-map>

Serialization for cmp-fields of Type byte[] Mapped to an Oracle Blob

In this release of WebLogic Server, cmp-fields of type byte[] mapped to a Blob are not serialized by default; the EJB container persists the byte[] directly and does not serialize it.

To cause WebLogic Server to serialize cmp-fields of type byte[] mapped to a Blob in an Oracle database, set the serialize-byte-array-to-oracle-blob compatibility flag, which was introduced in WebLogic Server 8.1 SP02, to True.

Specifying a CLOB Column Using the Deployment Descriptor

The following XML code shows how to specify a CLOB object using the dbms-column element in weblogic-cmp-jar-xml.

<field-map>
    <cmp-field>description</cmp-field>
    <dbms-column>product_description</dbms-column>
    <dbms_column-type>Clob</dbms-column-type>
    <dbms-default-value>Oracle</dbms-default-value>
</field-map>

Optimized CLOB Column Insertion on Oracle 10g

The Oracle 9i and 10g drivers have different requirements for successful insertion of CLOB column values into database rows. The Oracle 9i driver requires that a database row is locked before a CLOB value can be inserted into it. As a result, on Oracle 9i, WebLogic Server does the following to insert a row that contains a CLOB column value into a table:

  1. Inserts a row with all values other than the CLOB column into the table.

  2. Issues a SELECT FOR UPDATE statement on the row created in step 1, above.

  3. Inserts the CLOB value into the row.

While these steps are necessary for successful insertion of a row that contains a CLOB column value on Oracle 9i, the steps cause an unnecessary performance hit on Oracle 10g. The Oracle 10g driver features improved handling of CLOBS and does not require a lock on a row before a CLOB column value can be inserted into it. On Oracle 10g, WebLogic Server uses a single INSERT statement to insert a row with a CLOB column value into a table, which results in increased performance of CMP EJBs.

To make use of this WebLogic Server optimization for Oracle 10g, you do not need to configure anything additional. Simply specify Oracle as your database and WebLogic Server checks to see if your Oracle version is Oracle 9i or Oracle 10g. If WebLogic Server identifies your database as Oracle 10g, rows containing CLOB values are inserted into tables in single INSERT statements. If WebLogic Server identifies your database as Oracle 9i, rows containing CLOB values are inserted into tables in three steps as previously described.

For more information, see "Handling CLOBs - Made easy with Oracle JDBC 10g" at http://www.oracle.com/technetwork/java/jms/index.html#DUPS_OK_ACKNOWLEDGE.

Specifying Field Groups

A field group represents a subset of a bean's container-managed persistence (CMP) and container-managed relationship (CMR) fields. To improve performance, you can put related fields in a bean into groups that are faulted into memory together as a unit.

You can associate a group with a query or relationship, so that when a bean is loaded as the result of executing a query or following a relationship, only the fields mentioned in the group are loaded.

A special group named "default" is used for queries and relationships that have no group specified. By default, the default group contains all of a bean's CMP fields and any CMR fields that add a foreign key to the bean's table.

A field can belong to multiple groups. In this case, the getXXX() method for the field faults in the first group that contains the field.

You specify field groups in the field-group element of weblogic-cmp-jar.xml file, as shown in Example 6-3.

Example 6-3 Specifying Field Groups

<weblogic-rdbms-bean>
    <ejb-name>XXXBean</ejb-name>
    <field-group>
        <group-name>medical-data</group-name>
        <cmp-field>insurance</cmp-field>
        <cmr-field>doctors</cmr-fields>
    </field-group>
</weblogic-rdbms-bean>

Ordering and Batching Operations

Multiple instances of the same container-managed persistence (CMP) entity bean are often changed in a single transaction. If the EJB container issues SQL for every CMP entity bean instance, updates can become a performance bottleneck.

The EJB batch operations features solves this problem by updating multiple entries in a database table in one batch of SQL statements. This can dramatically improve performance by doing multiple database inserts, deletes, or updates for CMP beans in one database round-trip.

To permit batch database inserts, updates or deletes, set the enable-batch-operations element in the weblogic-cmp-jar.xml file to True.

Operation Ordering

Database operation ordering prevents constraint errors by taking into account database dependencies, and ordering inserts, updates and deletes accordingly.

Enabling database ordering causes the EJB container to do two things:

  • Delay all database operations—insert, update, and delete—to commit time

  • Order database operations at commit time

For example, assume a Customer A, who is related to Salesman A. If Salesman A is deleted, and Customer A is assigned to Salesman B, the container would order the operations in this fashion:

  1. Update Customer A to refer to Salesman B.

  2. Remove Salesman A.

This ensures that Customer A never refers to a salesman that does not exist, which would cause a database referential integrity error.

To enable the EJB container to correctly order database operations for related beans, you must specify the relationship between the beans, in the weblogic-rdbms-relation of weblogic-cmp-jar.xml. Otherwise, database constraint errors may result when the EJB container attempts to perform the updates.

Batch Operations Guidelines and Limitations

When using batch operations, you must set the boundary for the transaction, as batch operations only apply to the inserts, updates or deletes between transaction begin and transaction commit.

Batch operations only work with drivers that support the addBatch() and executeBatch() methods. If the EJB container detects unsupported drivers, it reports that batch operations are not supported and disables batch operations.

There are several limitations on using batch operations:

  • You cannot use the Automatically Generating Primary Keys feature with batch operations if the generator-type is set to sybase or sqlServer. If you have enabled automatic primary key generation with either of these types, WebLogic Server automatically disables batch operations and issues a warning.

  • The total number of entries created in a single batch operation cannot exceed the max-beans-in-cache setting, which is specified in the weblogic-ejb-jar.xml file.

  • If you set the dbms-column-type element in weblogic-cmp-jar.xml to either Blob or Clob, batch operation automatically turns off because you will not save much time if a Blob or Clob column exists in the database table. In this case, WebLogic Server performs one insert per bean, which is the default behavior.

Using Query Caching (Read-Only Entity Beans)

You can choose to cache read-only entity EJBs at the query level. Caching read-only entity EJBs at the query level improves performance because it enables the EJBs to be accessed in cache by any finder, thereby avoiding the need to access the database. For information, see enable-query-caching.

Using SQL in Entity Beans

In this release of WebLogic Server, you can use EJB-QL or standard or database-specific SQL for entity beans that use container-managed persistence (CMP). Oracle recommends that you use EJB-QL (with or without WebLogic extensions) for most queries and use SQL only when needed (for instance, to make use of vendor-specific features that cannot be accessed without using vendor-specific SQL).

You can use SQL in queries that cache multiple related objects, to implement finder and select methods, or with stored procedures.

To use EJB-QL in queries in this release of WebLogic Server, you do not need to change any mapping information in weblogic-cmp-jar.xml. You simply continue to map each CMP and CMR field to database columns as you did in pre-9.0 releases of WebLogic Server. For information, see, Configuring Entity EJBs for Database Operations and Using Container-Managed Relationships (CMRs). To use SQL in queries, you must describe the shape of the SQL result with the sql-shape element. SQL shape primarily consists of the SQL tables and columns that are returned. The EJB containers uses the SQL shape together with the CMP and CMP field mappings to return objects from the query. For more information, see:

Using Container-Managed Relationships (CMRs)

Container-managed relationships (CMRs) are relationships that you define between two entity EJBs, analogous to the relationships between the tables in a database. If you define a CMR between two EJBs that are involved in the same processing task, your application can benefit from these features:

  • Related beans can be cached together, reducing the number of queries necessary to accomplish a processing task.

  • Batched database operations can be ordered correctly at the end of a transaction, avoiding data consistency problems.

  • Related beans can be deleted automatically, using the cascade delete feature.

The sections that follow describe the features and limitations of WebLogic Server CMRs. For instruction on configuring CMRs, see Defining Container-Managed Relationships (CMRs).

CMR Requirements and Limitations

You can define a relationship between two WebLogic Server entity beans that will be packaged in the same JAR and whose data persist in the same database. Entities that participate in the same relationship must map to the same datasource. WebLogic Server does not support relationships between entity beans that are mapped to different datasources. The abstract schema for each bean that participates in a container-managed relationship must be defined in the same ejb-jar.xml file.

EJB 2.1 states that if an entity bean does not have a local interface, the only CMR in which it can participate is a unidirectional one, from itself to another entity bean. However, WebLogic Server allows an entity bean with only a remote interface to:

  • Participate in CMRs that are bidirectional, or

  • Be the target of a unidirectional CMR with another entity.

Because this feature is not specified in EJB 2.1, entity beans that have only remote interfaces, and either participate in bidirectional relationships or are the target of a unidirectional relationship, may not be portable to other application servers.

CMR Cardinality

An entity bean can have a one-to-one, one-to-many, or many-to-many relationship with another entity bean.

CMR Direction

Any CMR, whether one-to-one, one-to-many, or many-to-many, can be either unidirectional or bidirectional. The direction of a CMR determines whether the bean on one side of the relationship can be accessed by the bean on the other side.

Unidirectional CMRs can be navigated in one direction only—the "dependent bean" is unaware of the other bean in the relationship. CMR-related features such as cascade deletes can only be applied to the dependent bean. For example, if cascade deletes have been configured for a unidirectional CMR from to EJB1 to EJB2, deleting EJB1 will cause deletion of EJB2, but deleting EJB2 will not cause deletion of EJB1.


Note:

For the cascade delete feature, the cardinality of the relationship is a factor—cascade deletes are not supported from the many side of a relationship, even if the relationship is bidirectional.

Bidirectional relationships can be navigated in both directions—each bean in the relationship is aware of the other. CMR-related features are supported in both directions. For example, if cascade deletes have been configured for a bidirectional CMR between EJB1 to EJB2, deleting either bean in the CMR will cause deletion of the other bean.

Removing CMRs

When a bean instance that participates in a relationship is removed, the container automatically removes the relationship. For instance, given a relationship between an employee and a department, if the employee is removed, the container removes the relationship between the employee and the department as well.

Defining Container-Managed Relationships (CMRs)

Defining a CMR involves specifying the relationship and its cardinality and direction in ejb-jar.xml. You define database mapping details for the relationship and enable relationship caching in weblogic-cmp-jar.xml. These sections provide instructions:

Specifying Relationships in ejb-jar.xml

Container-managed relationships are defined in the ejb-relation element of ejb-jar.xml. Example 6-4 shows the ejb-relation element for a relationship between two entity EJBs: TeacherEJB and StudentEJB.

The ejb-relation element contains a ejb-relationship-role for each side of the relationship. The role elements specify each bean's view of the relationship.

Example 6-4 One-to-Many, Bidirectional CMR in ejb-jar.xml

<ejb-relation> 
    <ejb-relation-name>TeacherEJB-StudentEJB</ejb-relation-name>
    <ejb-relationship-role>
        <ejb-relationship-role-name>teacher-has-student
        </ejb-relationship-role-name>
        <multiplicity>One</multiplicity>
        <relationship-role-source>
            <ejb-name>TeacherEJB</ejb-name> 
        </relationship-role-source>
        <cmr-field>
            <cmr-field-name>teacher</cmr-field-name>
        </cmr-field>
    </ejb-relationship-role> 
    <ejb-relationship-role>
        <ejb-relationship-role-name>student-has-teacher
        </ejb-relationship-role-name>
        <multiplicity>Many</multiplicity>
        <relationship-role-source>
            <ejb-name>StudentEJB</ejb-name> 
        </relationship-role-source>
        <cmr-field>
            <cmr-field-name>student</cmr-field-name>
            <cmr-field-type>java.util.Collection</cmr-field-type>
        </cmr-field>
    </ejb-relationship-role>

Specifying Relationship Cardinality

The cardinality on each side of a relationship is indicated using the multiplicity element in its ejb-relationship-role element.

In Example 6-5, the cardinality of the TeacherEJB-StudentEJB relationship is one-to-many—it is specified by setting multiplicity to one on the TeacherEJB side and Many on the StudentEJB side.

The cardinality of the CMR in Example 6-5, is one-to-one—the multiplicity is set to one in both role elements for the relationship.

Example 6-5 One-to-One, Unidirectional CMR in ejb-jar.xml

<ejb-relation> 
    <ejb-relation-name>MentorEJB-StudentEJB</ejb-relation-name>
    <ejb-relationship-role>
        <ejb-relationship-role-name>mentor-has-student
        </ejb-relationship-role-name>
        <multiplicity>One</multiplicity>
        <relationship-role-source>
            <ejb-name>MentorEJB</ejb-name> 
        </relationship-role-source>
        <cmr-field>
            <cmr-field-name>mentorID</cmr-field-name>
        </cmr-field>
    </ejb-relationship-role> 
    <ejb-relationship-role>
        <ejb-relationship-role-name>student-has-mentor
        </ejb-relationship-role-name>
        <multiplicity>One</multiplicity>
        <relationship-role-source>
            <ejb-name>StudentEJB</ejb-name> 
        </relationship-role-source>
    </ejb-relationship-role> 

If a side of a relationship has a <multiplicity> of Many, its <cmr-field> is a collection, and you must specify its <cmr-field-type> as java.util.Collection, as shown in the StudentEJB side of the relationship in Example 6-4. It is not necessary to specify the cmr-field-type when the cmr-field is a single valued object.

Table 6-4 lists the contents of cmr-field for each bean in a relationship, based on the cardinality of the relationship.

Table 6-4 Cardinality and cmr-field-type

If relationship between EJB1 and EJB2 is ...EJB1's cmr-field contains ...EJB2's cmr-field contains ...

one-to-one

single valued object

single valued object

one-to-many

single valued object

Collection

many-to-many

Collection

Collection


Specifying Relationship Directionality

The directionality of a CMR is configured by the inclusion (or exclusion) of a cmr-field in the ejb-relationship-role element for each side of the relationship

A bidirectional CMR has a cmr-field element in the ejb-relationship-role element for both sides of the relationship, as shown in Figure 6-1.

A unidirectional relationship has a cmr-field in only one of the role elements for the relationship. The ejb-relationship-role for the starting EJB contains a cmr-field, but the role element for the target bean does not. Figure 6-1 specifies a unidirectional relationship from MentorEJB to StudentEJB— there is no cmr-field element in the ejb-relationship-role element for StudentEJB.

Specifying Relationships in weblogic-cmp-jar.xml

Each CMR defined in ejb-jar.xml must also be defined in a weblogic-rdbms-relation element in weblogic-cmp-jar.xml. weblogic-rdbms-relation identifies the relationship, and contains the relationship-role-map element, which maps the database-level relationship between the participants in the relationship, for one or both sides of the relationship.

The relation-name in weblogic-rdbms-relation must be the same as the ejb-relation-name for the CMR in ejb-jar.xml.

One-to-One and One-to-Many Relationships

For one-to-one and one-to-many relationships, relationship-role-map is defined for only one side of the relationship.

For one-to-one relationships, the mapping is from a foreign key in one bean to the primary key of the other.

Figure 6-1 is the weblogic-rdbms-relation element for a the one-to-one relationship between MentorEJB and StudentEJB, whose <ejb-relation> is shown in Figure 6-1.

Example 6-6 One-to-One CMR weblogic-cmp-jar.xml

<weblogic-rdbms-relation>
    <relation-name>MentorEJB-StudentEJB</relation-name>
    <weblogic-relationship-role>
       <relationship-role-name>
       mentor-has-student
       </relationship-role-name>
       <relationship-role-map>
          <column-map>
             <foreign-key-column>student</foreign-key-column>
             <key-column>StudentID/key-column>
          </column-map>
       </relationship-role-map>
    </weblogic-relationship-role>

For one-to-many relationships, the mapping is also always from a foreign key in one bean to the primary key of another. In a one-to-many relationship, the foreign key is always associated with the bean that is on the many side of the relationship.

Example 6-7 is the weblogic-rdbms-relation element for a the one-to-many relationship between TeacherEJB and StudentEJB, whose <ejb-relation> is shown in Figure 6-1.

Example 6-7 weblogic-rdbms-relation for a One-to-Many CMR

<weblogic-rdbms-relation>
    <relation-name>TeacherEJB-StudentEJB</relation-name>
    <weblogic-relationship-role>
        <relationship-role-name>
        teacher-has-student
        </relationship-role-name>
        <relationship-role-map>
        <column-map>
            <foreign-key-column>student</foreign-key-column>
            <key-column>StudentID/key-column>
        </column-map>
        </relationship-role-map>
    </weblogic-relationship-role>

Many-to-Many Relationships

For many-to-many relationships, specify a weblogic-relationship-role element for each side of the relationship. The mapping involves a join table. Each row in the join table contains two foreign keys that map to the primary keys of the entities involved in the relationship. The direction of a relationship does not affect how you specify the database mapping for the relationship.

Example 6-8 shows the weblogic-rdbms-relation element for the friends relationship between two employees.

The FRIENDS join table has two columns, first-friend-id and second-friend-id. Each column contains a foreign key that designates a particular employee who is a friend of another employee. The primary key column of the employee table is id. The example assumes that the employee bean is mapped to a single table. If employee bean is mapped to multiple tables, then the table containing the primary key column must be specified in the relation-role-map. For an example, see Specifying CMRs for EJBs that Map to Multiple Tables.

Example 6-8 weblogic-rdbms-relation for a Many-to-Many CMR

<weblogic-rdbms-relation>
    <relation-name>friends</relation-name>
    <table-name>FRIENDS</table-name>
    <weblogic-relationship-role>
        <relationship-role-name>first-friend
        </relationship-role-name>
        <relationship-role-map>
        <column-map>
            <foreign-key-column>first-friend-id</foreign-key-column>
            <key-column>id</key-column>
        </column-map
        </relationship-role-map>
    <weblogic-relationship-role>
    <weblogic-relationship-role>
        <relationship-role-name>second-friend</relationship-role-name>
        <relationship-role-map>
        <column-map>
            <foreign-key-column>second-friend-id</foreign-key-column>
            <key-column>id</key-column>
        </column-map>
    </relationship-role-map>
    </weblogic-relationship-role>
</weblogic-rdbms-relation>

Specifying CMRs for EJBs that Map to Multiple Tables

A CMP bean that is involved in a relationship may be mapped to multiple DBMS tables.

  • If the bean on the foreign-key side of a one-to-one or one-to-many relationship is mapped to multiple tables then the name of the table containing the foreign-key columns must be specified using the foreign-key-table element.

  • Conversely, if the bean on the primary-key side of a one-to-one or one-to-many relationship or a bean participating in a many-to-many relationship is mapped to multiple tables then the name of the table containing the primary-key must be specified using the primary-key-table element.

If neither of the beans in a relationship is mapped to multiple tables, then the foreign-key-table and primary-key-table elements may be omitted since the tables being used are implicit.

Example 6-9 contains a relationship-role-map for a CMR in which the bean on the foreign-key side of a one-to-one relationship, Fk_Bean, is mapped to two tables: Fk_BeanTable_1 and Fk_BeanTable_2.

The foreign key columns for the relationship, Fk_column_1 and Fk_column_2, are located in Fk_BeanTable_2. The bean on the primary key side, Pk_Bean, is mapped to a single table with primary-key columns Pk_table_pkColumn_1 and Pk_table_pkColumn_2.

The table that contains the foreign-key columns is specified by the <foreign-key-table> element.

Example 6-9 One-to-One CMR, One Bean Maps to Multiple Tables

<relationship-role-map
    <foreign-key-table>Fk_BeanTable_2</foreign-key-table>
    <column-map>
        <foreign-key-column>Fk_column_1</foreign-key-column>
        <key-column>Pk_table_pkColumn_1</key-column>
    </column-map>
    <column-map>
        <foreign-key-column>Fk_column_2</foreign-key-column>
        <key-column>Pk_table_pkColumn_2</key-column>
    </column-map>
</relationship-role-map>

About CMR Fields and CMR Field Accessor Methods

CMR fields are not stored as attributes of an implementation class—they are accessible in the bean through CMR field accessor methods that you write. CMR field accessor methods:

  • Must begin with get...() and set...() and the text following get.../set... must match the name of the relation field as it is declared in the ejb-jar.xml.

  • Must exist in the implementation class for every CMR field.

  • Must be declared abstract

To allow remote clients to use CMR field accessor methods, put the getter and/or setter method signatures in the remote interface. However, CMR fields of a Collection datatype cannot be exposed in the remote interface. A CMR field that is a Collection can only be accessed by local methods.

Using Cascade Delete for Entities in CMRs

When a cascade delete is performed, the deletion of a bean instance that participates in a relationship with another bean instance causes the container to also automatically delete all of the dependent bean instances. This feature is an efficient way to maintain data integrity.

For example, if the Employee bean has a one-to-many relationship to the Employee_Projects bean, deleting an Employee bean instance causes instances of the Employee_Projects bean to also be deleted.

You can specify cascade delete for one-to-one and one-to-many relationships; many-to-many relationships are not supported.

WebLogic Server supports two methods of cascade delete:

  • Java EE Cascade Delete—This method does not require that the underlying database have built-in support for cascade deletes. Configure the behavior using the cascade-delete element in ejb-jar.xml, as shown in the following example:

    <ejb-relation>
        <ejb-relation-name>Customer-Account</ejb-relation-name>
            <ejb-relationship-role>
                <ejb-relationship-role-name>Account-Has-Customer
                </ejb-relationship-role-name>
            <multiplicity>one</multiplicity>
                <cascade-delete/> 
        </ejb-relationship-role>
    </ejb-relation>
    

    Note:

    The cascade-delete element can only be specified for a ejb-relationship-role element if the other ejb-relationship-role in the relationship has multiplicity of one.

  • Database-Level Cascade Delete (Oracle only)—This method allows an application to take advantage of a database's built-in support for cascade delete, and possibly improve performance. When db-cascade-delete is enabled, the underlying database must be set up for cascade deletes. For instructions and examples of setting up database cascade delete in Oracle WebLogic Server, db-cascade-delete.

In a high volume transaction environment, transactions that use exclusive concurrency can encounter deadlocks when a transaction that performs a cascade delete needs access to the same entity bean as a transaction that does not perform a cascade delete. For information on how to avoid such deadlocks, see Deadlock Prevention for Exclusive Concurrency and Cascade Deletes.

Relationship Caching

Relationship caching—also known as "pre-fetching" or "eager relationship caching'—improves the performance of entity beans by loading related beans into the cache and preventing multiple queries by issuing a join query for the related bean. If a set of beans is accessed as part of the same unit of work, then your application should load them into cache at the same time.

Suppose your application contains entity beans with the following relationships:

customerBean has a one-to-many relationship with  accountBean
accountBean has a one-to-one relationship with addressBean
customerBean has a one-to-one relationship with phoneBean

Consider the following EJB code for accountBean and addressBean, which have a 1-to-1 relationship:

Account acct = acctHome.findByPrimaryKey("103243"); 
Address addr = acct.getAddress(); 

Without relationship caching, an SQL query is issued by the first line of code to load the accountBean and another SQL query is issued by the second line of code to load the addressBean; this results in two queries to the database.

With relationship caching, a single query is issued to load both accountBean and addressBean by the first line of code, which should result in better performance. So, if you know that a related bean will be accessed after executing a particular finder method, it is a good idea to let the finder method know via the relationship caching feature.

The relationship caching feature has the following limitations:

  • Relationship caching is supported for one-to-one, one-to-many, and many-to-one relationships. It is not supported for many-to-many relationships.

  • When using weblogic-ql, this feature only works with finder methods that return references to either EJBObject or EJBLocalObject beans.

If you enable relationship caching for a finder or a select method, the result of the query will always be a distinct set even if the distinct keyword is not specified. This is due to a technical limitation that does not allow the EJB container to distinguish duplicates in the underlying JDBC result set.

With relationship caching enabled, changes to the relationship are automatically reflected in cache. For instance, if an instance is added on the "many" side of a one-to-many relationship, that change is reflected in the cached relationship—a subsequent query to the bean on the "one" side of the relationship causes the relationship to be refreshed in cache, so that the new instance is available to the query.

Enabling Relationship Caching

To enable relationship caching:

  1. Specify the caching-name element in the weblogic-query element of the weblogic-cmp-jar.xml file.

    If a caching-name element is specified in the weblogic-query element, when the finder query is executed, WebLogic Server loads data for related beans as specified by the relationship-caching element that the caching-name element specifies.

  2. Make sure that the finders-load-bean element (in weblogic-ejb-jar.xml) for the bean that contains the finder is not set to False or relationship caching will not be enabled. The default value of finder-load-bean is True.

  3. Specify the database-type element in the weblogic-cmp-jar.xml file. Relationship caching uses outer joins for queries and outer join syntax can vary by database type.

Because relationship caching uses join queries, the number of caching-element elements in the relationship-caching element can increase duplicates in the result set. Specify one one-to-many relationships per caching-element to avoid duplicates in the result set.

Specify the relationship-caching element in weblogic-cmp-jar.xml, as shown in this example:

<relationship-caching>
    <caching-name>cacheMoreBeans</caching-name>
    <caching-element>
        <cmr-field>accounts</cmr-field>
        <group-name>acct_group</group-name>
        <caching-element>
            <cmr-field>address</cmr-field>
            <group-name>addr_group</group-name>
        </caching-element>
    </caching-element>
    <caching-element>
        <cmr-field>phone</cmr-field>
        <group-name>phone_group</group-name>
    </caching-element>
</relationship-caching>

The accounts and phone fields are cmr-fields in customerBean; the address field is a cmr-field in the accountBean; and addr_group and phone_group are groups in addressBean and phoneBean.

Using nested caching-element elements enables the bean to load more than one level of related beans. In the above sample, addressBean is the second level related bean because it is nested in the accountBean. Currently, there is no limitation on the number of caching-elements that you can specify. However, setting too many caching-element levels could have an impact on the performance of the current transaction.

Choosing a Concurrency Strategy

An entity bean's concurrency strategy specifies how the EJB container should manage concurrent access to the bean; it determines how and when WebLogic Server synchronizes its cached copy of the entity with the database.

Concurrency strategies supported by WebLogic Server are described in the following sections.

Exclusive Concurrency

With exclusive concurrency, the container places an exclusive lock on cached EJB instances when the bean is associated with a transaction. Other requests for the EJB instance are blocked until the transaction completes. Exclusive locks are local to the server instance, so this strategy is most appropriate for a single server architecture. When used in a cluster, exclusive concurrency serializes all requests to a bean instance within a server instance, but concurrency between servers in the cluster that access the same bean concurrently is governed by the database.

Multiple clients can use the exclusive concurrency option to access entity EJBs in a serial fashion. Using this exclusive option means that if two clients simultaneously attempt to access the same entity EJB instance (an instance having the same primary key), the second client is blocked until the EJB is available.

Database Concurrency

With database concurrency, concurrency control for an EJB for each transaction is deferred to the underlying datastore. WebLogic Server allocates a separate entity bean instance to each transaction and allows concurrency control to be handled by the database. This is the default option.

With the Database mechanism, the EJB container continues to cache instances of entity bean instances. However, the container does not cache the intermediate state of a bean instance between transactions. Instead, WebLogic Server issues a SQL SELECT for each instance at the beginning of a transaction to obtain the latest EJB data. A SQL UPDATE is issued if there are changes.

The request to commit data is subsequently passed along to the database. The database, therefore, handles all concurrency control and deadlock detection for the EJB's data.

Optimistic Concurrency

As with the Database concurrency strategy, Optimistic concurrency gives each transaction its own bean instance. The Optimistic concurrency strategy does not hold any locks in the EJB container or the database while the transaction is in process.


Note:

For databases that do read-locking (non-Oracle databases) optimistic beans read data in a separate, local transaction. The local transaction commits as soon as the read completes. This strategy avoids read locks and can allow for better scalability when transactions do not update the same data concurrently.

Preventing Stale Optimistic Bean Data

To prevent optimistic data from going stale, the container activates a new bean instance for each transaction so that requests proceed in parallel. WebLogic Server calls ejbLoad() for entity beans based on the value specified in read-timeout-seconds, provided the value of cache-between-transactions is True.

Explicit Invalidation of Optimistic Beans

You can invalidate optimistic beans explicitly when the underlying data is updated outside the EJB container (this is also known as a "backdoor update"). For information, see Invalidating Entity EJBs Explicitly.

Invalidation Options for Optimistic Concurrency in Clusters

By default, when a bean that has a concurrency-strategy of Optimistic is deployed in a cluster and a member of the cluster updates the bean, the EJB container attempts to invalidate all copies of the bean in all servers in the cluster. This invalidation allows you to avoid optimistic concurrency failures, but can be a drain on performance because it is a resource-intensive operation. If you prefer, you can set cluster-invalidation-disabled in weblogic-cmp-jar.xml to True to prevent the EJB container from attempting to invalidate copies of the bean across the cluster.

Check Data for Validity with Optimistic Concurrency

You can configure the EJB container to validate an Optimistic bean's transaction data before committing the transaction, to verify that no data read or updated by the transaction has bean changed by another transaction. If it detects changed data, the EJB container rolls back the transaction.


Note:

The EJB container does not validate Blob or Clob fields in a bean with Optimistic concurrency. The workaround is to use version or timestamp checking.

Configure validity checking for a bean with Optimistic concurrency using the verify-columns and verify-rows elements in the table-map element for the bean in weblogic-cmp-jar.xml file.

The verify-rows element specifies the rows in a table that the EJB container should check when optimistic concurrency is used; the verify-columns element specifies how columns in a table are checked for validity when you use the optimistic concurrency strategy.

  1. Set the verify-rows element to:

    • Read—To check all rows in the table that have been read during the transaction. This includes both rows that are simply read and rows that are read and then updated or deleted by the transaction. Checking all rows entails additional overhead because it generally increases the amount of optimistic checking that must be performed by the EJB container. With the Read option, committed transactions read a set of rows that are guaranteed not to be modified by another transaction until after the transaction commits. This results in a high level of consistency which is very close to the ANSI definition of SERIALIZABLE consistency.

    • Modified—To check only the rows that have been updated or deleted by the current transaction. This setting ensures that two transactions will not update the same row concurrently, resulting in a lost update, but it allows reads and updates of different transactions to be interleaved. This results in a level of consistency that falls between the ANSI READ_COMMITTED and REPEATABLE_READ levels of consistency.

  2. Set the value of the verify-columns element to:

    • Read—To check all columns in the table that have been read during the transaction. This includes both rows that are simply read and rows that are read and then updated or deleted by the transaction.

    • Modified—To check only the columns that have been updated or deleted by the current transaction.


      Note:

      If verify-rows is set to Read then the verify-columns element cannot have a value of Modified since this combination would result in only checking the modified rows.

    • Version—To check that a version column exists in the table and that this column is used to implement optimistic concurrency.

      A version column must be created with an initial value of 0 or any positive integer, and must increment by 1 whenever the row is modified. For more information, see version-column-initial-value.

      Additionally, if you use database triggers to update version columns in the database and you set trigger-updates-optimistic-column to True, the database triggers must initialize the version column in the database when the bean is created.

    • Timestamp—To check that a timestamp column exists in the table and that this column is used to implement optimistic concurrency. Timestamp-based optimistic concurrency requires a 1 second granularity for the database column.

    By default, the EJB container manages the version and timestamp columns and ensures that these columns are kept up to date. If you choose to instead let database triggers maintain version and timestamp columns, set the value of trigger-updates-optimistic-column to True.


    Note:

    The version or timestamp column is not updated if the transaction did not modify any regular CMP or CMR fields—if the only data changed during the transaction was the value of the version or timestamp column (as a result of transaction initiation) the column used for optimistic checking will not be updated at the end of the transaction.

  3. If verify-columns is set to Version or Timestamp:

    1. Specify the version or timestamp column using the optimistic-column in the table-map element in the weblogic-cmp-jar.xml file. Mapping this column to a cmp-field is optional.

      The optimistic-column element identifies a database column that contains a version or timestamp value used to implement optimistic concurrency. This element is case maintaining, though not all databases are case sensitive. The value of this element is ignored unless verify-columns is set to Version or Timestamp.

    2. Specify the initial value of the version column using the version-column-initial-value element in the weblogic-cmp-jar.xml file.

If the EJB is mapped to multiple tables, optimistic checking is only performed on the tables that are updated during the transaction.

Optimistic Concurrency and Oracle Databases

For Oracle databases, if you set verify-columns to Modified for an entity EJB with a CMP non-key field type java.util.Date and implementation type Oracle DATE, WebLogic Server throws an optimistic concurrency violation exception when a simple update is made to the non-key DATE field—even though only one user is updating the record.

This problem occurs because of a mismatch in date value precision between the Oracle DATE column and the java.util.Date type. The java.util.Date type is in milliseconds, and the Oracle DATE column is not. There are two ways to avoid this error:

  • Set the Oracle database column type to Timestamp, a higher precision type introduced in Oracle9i.

  • Include logic in your application to zero out the milliseconds of a java.util.Date value. To accomplish this, prepare a date field for an entity bean java.util.Date field in this way:

    Calendar cal = Calendar.getInstance(); 
    cal.set(Calendar.MILLISECOND, 0); // clears millisecond
    Date myDate = cal.getTime(); 
    

Read Only Concurrency

Used to signify that a bean is read-only. The container activates a new bean instance for each transaction so that requests proceed in parallel. WebLogic Server calls ejbLoad() for read-only beans based on the read-timeout-seconds parameter.

To allow generation of more efficient code for read-only beans, create and remove operations are not allowed for EJBs that use ReadOnly concurrency in this release of WebLogic Server.

To allow read-only beans to use create and remove operations—for instance, to support legacy behavior—set the allow-readonly-create-and-remove element in weblogic-cmp-jar.xml to True.

Concurrency Strategy Trade-Offs

Concurrency strategies present a trade-off between performance and freshness of data. You should choose a concurrency strategy based on which of these factors weighs more heavily in your application. The trade-offs are summarized in Table 6-5.

Table 6-5 Concurrency Strategy Trade-offs

Concurrency StrategyBenefitsRisks and LimitationsWhen to Choose It

Database

Deferring concurrency control to the database improves throughput, compared to exclusive concurrency, for concurrent access to data and provides deadlock detection.

Risk of deadlock, as each transaction must obtain an update lock from the database.

Mitigate deadlock risk by setting use-select-for-update in weblogic-cmp-jar.

xml. This causes the database to take out an exclusive lock when the read is done, avoiding the deadlock that can occur when a read lock is upgraded to an exclusive lock.

Makes the bean more dependent on the database's lock policies, which might reduce the bean's portability.

If the database concurrency control is sufficient for your application and you do not require additional features provided by the container.

Note: Use the transaction-isolation element in combination with Database concurrency to achieve the desired concurrency behavior.

Optimistic

Provides highest level of concurrent access, as it holds no locks in the EJB container or database during a transaction.

Multiple transactions can access the same application data at the same time.

If multiple transactions are unlikely to attempt to modify the same application data at the same time.

Exclusive

Serializes access to EJB data in a single server (non-clustered environment) for a high level of consistency. Avoids deadlocks due to lock upgrades, and prevents unnecessary calls to ejbLoad() to refresh the bean instance's persistent fields.

Performance degradation can result. Once a client has locked an EJB instance, other clients are blocked from the EJB's data, even those who require only read-access.

To provide backwards compatibility for applications that rely on this strategy.

For applications in which a high level of concurrency is essential, and more important than performance.

Read Only

N/A

N/A

N/A


Configuring Concurrency Strategy

Specify the concurrency mechanism for a bean by setting the concurrency-strategy element in the entity-cache element in weblogic-ejb-jar.xml. Because concurrency-strategy is defined at the bean level, different beans in the same application can use different concurrency strategies, as appropriate.

If you do not specify a concurrency-strategy, WebLogic Server uses Database concurrency by default.

Deadlock Prevention for Exclusive Concurrency and Cascade Deletes

In situations of high throughput, transactions that use an exclusive concurrency strategy can encounter deadlocks if a transaction that performs a cascade delete needs access to the same entity bean as a transaction that does not perform a cascade delete.

You can prevent such deadlocks with the lock-order element of weblogic-cmp-jar.xml deployment descriptor file. lock-order defines the order in which beans are locked during a cascade delete of related beans. Its value is an integer value. The bean with the lowest lock-order value is processed first, the bean with the next lowest lock-order value is processed next, and so on.

The locking order specified should be the same as the locking order used by other transactions in the application.

lock-order causes a cascade delete to lock bean instances in the same order as their other transactions. If the normal lock order is BeanA, then BeanB, specify this lock-order, and cascade delete will use it.

Using the Read-Mostly Pattern

For persistent data that is only occasionally updated, you can implement a "read-mostly pattern" in WebLogic Server by mapping a read-only and a read-write entity bean to the same data. You use the read-only entity bean for reads and the read-write entity bean for writes.

The read-only entity EJB loads bean data at intervals specified by the read-timeout-seconds element in the entity-cache (or entity-cache-ref) element for the bean in weblogic-ejb-jar.xml. To ensure that the read-only bean always returns current data, the read-only bean must be invalidated when the read-write bean changes the entity bean data. You can configure WebLogic Server to automatically invalidate the read-only bean, or explicitly invalidate it in bean code, as described in Invalidating Read-Only Entity EJBs Implicitly and Invalidating Entity EJBs Explicitly respectively.

In a WebLogic Server cluster, the read-mostly pattern gives clients of the read-only EJB the performance advantage of reading from cache, while clients of the read-write EJB enjoy true transactional behavior—the read-write EJB's cached state always matches the persistent data in the database.

Configuring Entity Beans for Read-Mostly Pattern

These practices will reduce the likelihood of data consistency problems with the read-mostly pattern.

  • Configuring the read-only beans' read-timeout-seconds element in weblogic-ejb-jar.xml:

    • To the same value in all beans that can be updated in the same transaction.

    • To the shortest period that yields acceptable performance levels.

  • Design read-write beans:

    • To update the minimum data set necessary; avoid implementing beans that write numerous, unchanged fields to the datastore at each ejbStore().

    • To update their data on a timely basis; do not use a read-write bean in lengthy transactions that might run longer than the read-timeout-seconds setting for its read-only counterparts.

    • To invalidate the read-only counterpart of a read-write bean when the read-write bean updates bean data.

If you are running EJB 2.x, you can approximate the read-mostly pattern using a single bean that uses optimistic concurrency. An optimistic bean acts like a read-only bean when performing a read—it reads from the cache and can return stale data. However, when an optimistic bean performs a write, the container ensures that the data being updated has not changed—providing the same level of consistency for writes as a bean that uses Database concurrency. See Choosing a Concurrency Strategy.

Invalidating Read-Only Entity EJBs Implicitly

The invalidation-target element in the entity-descriptor element in weblogic-ejb-jar.xml identifies a read-only entity EJB that should be invalidated when a CMP entity bean has been modified.

invalidation-target may only be specified for an EJB 2.x CMP entity bean. The target ejb-name must be a read-only entity EJB.

Invalidating Entity EJBs Explicitly

In this release of WebLogic Server, you can invalidate any optimistic entity bean that has cache-between-transactions enabled, by calling the following invalidate() method on either the CachingHome or CachingLocalHome interface.

Example 6-10 CachingHome and CachingLocalHome interfaces

package weblogic.ejb;

public interface CachingHome {
    public void invalidate(Object pk) throws RemoteException;
    public void invalidate (Collection pks) throws RemoteException;
    public void invalidateAll() throws RemoteException;

public interface CachingLocalHome {
    public void invalidate(Object pk) throws RemoteException;
    public void invalidate (Collection pks) throws RemoteException;
    public void invalidateAll() throws RemoteException
}

The following example code shows how to cast the home to CachingHome and then call the method:

Example 6-11 Casting the Home and Calling the Method

import javax.naming.InitialContext; 
import weblogic.ejb.CachingHome;

Context initial = new InitialContext(); 
Object o = initial.lookup("CustomerEJB_CustomerHome"); 
CustomerHome customerHome = (CustomerHome)o;

CachingHome customerCaching = (CachingHome)customerHome; 
customerCaching.invalidateAll();

The invalidate() method causes the entity beans to be invalidated in the local server instance. If the server instance is a member of a cluster, it multicasts a message to the other clustered servers to invalidate their cached copies of the bean. Upon the next getXXX() to an invalidated entity bean, the container loads the current version of the bean's persistent data to the entity cache from the database, as described in Understanding ejbLoad() and ejbStore() Behavior.

WebLogic Server calls invalidate() after the update transaction has completed. If the invalidation occurs during a transaction update, the previous version might be read if the isolation-level for transactions does not permit reading uncommitted data.

CMP Entity Bean Descriptors Element by Feature

The following sections are a quick reference to WebLogic Server-specific deployment for CMP entity beans. Each section contains the elements related to a particular type of feature or behavior. The table in each section defines relevant elements terms of: the behavior it controls, the parent element in weblogic-cmp-jar.xml that contains the element, and the behavior you can expect if you do not explicitly specify the element in weblogic-cmp-jar.xml.

Container-Managed Relationship Elements

The following lists the container-managed relationship elements in weblogic-cmp-jar.xml.

Table 6-6 Container-managed Relationship Elements in weblogic-cmp-jar.xml

ElementDescription

relation-name


Name of the relationship.

Note: If an ejb-relation-name for the relationship is specified in ejb-jar.xml, relation-name must contain the same value as ejb-relation-name.

relationship-role-name


The name of the relationship role. (A relationship has two roles—one for each side of the relationship).

For a 1-1 or 1-m relationship, specify only the role on the foreign-key side. For examples, see Defining a One-to-One Relationship and Defining a One-to-Many Relationship.

For a m:m relationship, specify the roles on both sides of the relationship. roles. For an example, see Defining a Many-to-Many Relationship.

Note: The value of <relationship-role-

name> should match the name of an ejb-relationship-role in ejb-jar.xml.

foreign-key-column

Specifies the target side of the key column mapping for the relationship—the foreign key column.

key-column

Specifies the initiating side of the key column mapping for the relationship—the primary key column.


Primary Key Elements

The following lists the primary key elements in weblogic-cmp-jar.xml.

Table 6-7 Primary Key Elements in weblogic-cmp-jar.xml

ElementDescriptionDefault

generator-type


Identifies the facility used to generate primary keys. Values include Oracle, SQLServer, or SQLServer2000, NamedSequenceTable.

n/a

generator-name


Defines the Oracle SEQUENCE, or the name of a SEQUENCE table used.

n/a

key-cache-size


Specifies the size of the key cache.

1

create-default-dbms-table


Determines behavior related to if and how the EJB container will create database tables.

Disabled


PKy!h!PK;wEOEBPS/deploy.htmBc Deployment Guidelines for Enterprise JavaBeans

8 Deployment Guidelines for Enterprise JavaBeans

The following sections contain EJB-specific deployment guidelines. For deployment topics that are common to all deployable application units, you will see cross-references to topics in Deploying Applications to Oracle WebLogic Server, a comprehensive guide to deploying WebLogic Server applications and modules.

Before You Deploy an EJB

Before starting the deployment process you should have:

  • Functional, tested bean code, in an exploded directory format or packaged in an archive file—a JAR for a stand-alone EJB or an EAR if the EJB is part of an enterprise application—along with the deployment descriptors. For production environments, Oracle recommends that you package your application as an EAR.

    For an overview of the steps required to create and package an EJB, see Overview of the EJB Development Process.

  • Configured the required deployment descriptors—ejb-jar.xml and weblogic-ejb-jar.xml, and, for entity EJBs that use container-managed persistence, weblogic-cmp-jar.xml.

    To create EJB deployment descriptors, see Generate Deployment Descriptors.

Understanding and Performing Deployment Tasks

Table 8-1 is a guide to WebLogic Server documentation topics that help you make decisions about deployment strategies and provide instructions for performing deployment tasks. For EJB-specific deployment topics, see Deployment Guidelines for EJBs.

Table 8-1 Deployment Tasks and Topics

If You Want To....See This Topic

Deploy in a development environment

"Deploying and Packaging from a Split Development Directory" in Developing Applications for Oracle WebLogic Server.

Select a deployment tool

"Deployment Tools" in Deploying Applications to Oracle WebLogic Server

Determine appropriate packaging for a deployment

"Preparing Applications and Modules for Deployment" in Deploying Applications to Oracle WebLogic Server.

Organizing EJB components in a split directory structure.

"EJBs" in Developing Applications for Oracle WebLogic Server.

Select staging mode

"Controlling Deployment File Copying with Staging Modes" in Deploying Applications to Oracle WebLogic Server.

Perform specific deployment tasks

"Overview of the Deployment Process" in Deploying Applications to Oracle WebLogic Server.


Deployment Guidelines for EJBs

The following sections provide guidelines for deploying EJBs.

Deploy EJBs as Part of an Enterprise Application

Oracle recommends that you package and deploy your stand-alone EJB applications as part of an Enterprise application. An Enterprise application is a Java EE deployment unit that bundles together Web applications, EJBs, and Resource Adapters into a single deployable unit.

This is a Oracle best practice, which allows for easier application migration, additions, and changes. Also, packaging your applications as part of an Enterprise application allows you to take advantage of the split development directory structure, which provides a number of benefits over the traditional single directory structure. See "Overview of the Split Development Directory Environment" in Developing Applications for Oracle WebLogic Server.

Deploy EJBs That Call Each Other in the Same Application

When an EJB in one application calls an EJB in another application, WebLogic Server passes method arguments by value, due to classloading requirements. When EJBs are in the same application, WebLogic Server can pass method arguments by reference; this improves the performance of method invocation because parameters are not copied.

For best performance, package components that call each other in the same application, and set enable-call-by-reference in weblogic-ejb-jar.xml to True. (By default, enable-call-by-reference is False.)

Deploying EJBs that Use Dependency Injection

When an EJB uses dependency injection, the resource name defined in the class and the superclass must be unique. For example:

public class ClientServlet extends HttpServlet {
    @EJB(name = 'DateServiceBean', beanInterface = DateService.class)
    private DateService bean; .... } 
public class DerivedClientServlet extends ClientServlet { 
    @EJB(name = MyDateServiceBean', beanInterface = DateService.class)
    private DateService bean; .... }
 

For more information about dependency injection, see "Using Java EE Annotations and Dependency Injection" in Developing Applications for Oracle WebLogic Server.

Deploy Homogeneously to a Cluster

If your EJBs will run on a WebLogic Server cluster, Oracle recommends that you deploy them homogeneously—to each Managed Server in the cluster. Alternatively, you can deploy an EJB to only to a single server in the cluster (that is, "pin" a module to a server). This type of deployment is less common, and should be used only in special circumstances where pinned services are required. For more information, "Understanding Cluster Configuration" in Using Clusters for Oracle WebLogic Server.

Deploying Pinned EJBs to a Cluster

There is a known issue with deploying or redeploying EJBs to a single server instance in a cluster—referred to as pinned deployment—if the JAR file contains contain uncompiled classes and interfaces.

During deployment, the uncompiled EJB is copied to each server instance in the cluster, but it is compiled only on the server instance to which it has been deployed. As a result, the server instances in the cluster to which the EJB was not targeted lack the classes generated during compilation that are necessary to invoke the EJB. When a client on another server instance tries to invoke the pinned EJB, it fails, and an Assertion error is thrown in the RMI layer.

If you are deploying or redeploying an EJB to a single server instance in a cluster, compile the EJB with appc before deploying it, to ensure that the generated classes are copied to all server instances available to all nodes in the cluster.

For more information on pinned deployments, see "Deploying to a Single Server Instance (Pinned Deployment)" in Using Clusters for Oracle WebLogic Server.

Redeploying an EJB

When you make changes to a deployed EJB's classes, you must redeploy the EJB. If you use automatic deployment, deployment occurs automatically when you restart WebLogic Server. Otherwise, you must explicitly redeploy the EJB.

Redeploying an EJB deployment enables an EJB provider to make changes to a deployed EJB's classes, recompile, and then "refresh" the classes in a running server.

When you redeploy, the classes currently loaded for the EJB are immediately marked as unavailable in the server, and the EJB's classloader and associated classes are removed. At the same time, a new EJB classloader is created, which loads and maintains the revised EJB classes.

When clients next acquire a reference to the EJB, their EJB method calls use the changed EJB classes.

You can redeploy an EJB that is standalone or part of an application, using the weblogic.Deployer tool or the Administration Console. For instructions, see "Redeploying Applications in a Production Environment" in Deploying Applications to Oracle WebLogic Server.

Production redeployment is not supported for:

  • applications that use JTS drivers.

  • applications that include EJB 1.1 container-managed persistence (CMP) EJBs. To use production redeployment with applications that include CMP EJBs, use EJB 2.x CMP instead of EJB 1.1 CMP.

For more information on production redeployment limitations, see "Requirements and Restrictions for Production Redeployment" in Deploying Applications to Oracle WebLogic Server.

Using FastSwap Deployment to Minimize Deployment

During iterative development of an EJB application, you make many modifications to the EJB implementation class file, typically redeploying an EJB module multiple times during its development.

Java EE 5 introduces the ability to redefine a class at runtime without dropping its ClassLoader or abandoning existing instances. This allows containers to reload altered classes without disturbing running applications, vastly speeding up iterative development cycles and improving the overall development and testing experiences.

With FastSwap, Java classes are redefined in-place without reloading the ClassLoader, thereby having the decided advantage of fast turnaround times. This means that you do not have to wait for an application to redeploy for your changes to take affect. Instead, you can make your changes, auto compile, and then see the effects immediately.

For more information about FastSwap, see "Using FastSwap Deployment to Minimize Redeployment" in Deploying Applications to Oracle WebLogic Server.

Understanding Warning Messages

To get information about a particular warning, use the weblogic.GetMessage tool. For example:

java weblogic.GetMessage -detail -id BEA-010202

Disabling EJB Deployment Warning Messages

You can disable certain WebLogic Server warning messages that occur during deployment. You may find this useful if the messages provide information of which you are already aware.

For example, if the methods in your EJB makes calls by reference rather than by value, WebLogic Server generates this warning during deployment: "Call-by-reference not enabled."

You can use the disable-warning element in weblogic-ejb-jar.xml to disable certain messages. For a list of messages you can disable, and instructions for disabling the messages, see disable-warning.

PKXɗBBPK;wEOEBPS/dd_reference.htm Deployment Descriptor Schema and Document Type Definitions Reference

A Deployment Descriptor Schema and Document Type Definitions Reference

In this release of WebLogic Server, deployment descriptors are XML Schema Definition-based (XSD). In pre-9.0 releases of WebLogic Server, deployment descriptors were Document Type Definition-based (DTD). For backward compatibility, this release of WebLogic Server supports XSD- or DTD-based deployment descriptors; you can deploy applications that use DTD-based descriptors without modifying them.

The following sections describe EJB XSD-based deployment descriptors and namespace declarations for this release of WebLogic Server as well as EJB DTD-based deployment descriptors and DOCTYPE headers for deployment descriptors from pre-9.0 releases of WebLogic Server.

For information on the elements in WebLogic Server EJB deployment descriptors, see the following sections:

For information on the EJB 1.1 deployment descriptor elements, see Appendix F, "Important Information for EJB 1.1 Users."

XML Schema Definitions and Namespace Declarations

The contents and arrangement of elements in your deployment descriptor files must conform to the appropriate XSD.

An XSD deployment descriptor file requires a namespace declaration in the root element of the file. Namespace declarations in the root element of a deployment descriptor file apply to all elements in the descriptor unless a specific element includes another namespace declaration that overrides the root namespace declaration.


Note:

If you use DDConverter to convert your DTD-based deployment descriptors to XSD-based, the correct namespace declaration is automatically written to your descriptor files.

Oracle recommends that you always include the schema location URL along with the namespace declaration in your XML deployment descriptor files; if you do not include the schema location in your XML deployment descriptor files, you may not be able to edit the descriptor files with a third-party tool.

weblogic-ejb-jar.xml Namespace Declaration and Schema Location

The correct text for the namespace declaration and schema location for the WebLogic Server weblogic-ejb-jar.xml file is as follows.

<weblogic-ejb-jar xmlns="http://xmlns.oracle.com/weblogic/weblogic-ejb-jar" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.oracle.com/weblogic/weblogic-ejb-jar" http://xmlns.oracle.com/weblogic/weblogic-ejb-jar/1.2/weblogic-ejb-jar.xsd "> 
... 
</weblogic-ejb-jar>

weblogic-cmp-jar.xml Namespace Declaration and Schema Location

The correct text for the namespace declaration and schema location for the WebLogic Server weblogic-cmp-jar.xml file is as follows.

<weblogic-rdbms-jar xmlns="http://xmlns.oracle.com/weblogic/weblogic-rdbms-jar" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.oracle.com/weblogic/weblogic-rdbms-jar/1.2/weblogic-rdbms-jar.xsd"> 
... 
</weblogic-rdbms-jar>

ejb-jar.xml Namespace Declaration and Schema Location

The correct text for the namespace declaration and schema location for the Enterprise JavaBeans 2.1 ejb-jar.xml file is as follows.

<ejb-jar xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/ejb-jar_2_1.xsd"> 
... 
</ejb-jar>

Document Type Definitions and DOCTYPE Header Information

In prior releases of WebLogic Server, the contents and arrangement of elements in your deployment descriptor files must have conformed to the appropriate DTD.

WebLogic Server ignores the DTD locations embedded within the DOCTYPE header of XML deployment files, and instead uses the DTD locations that were installed along with the server. However, the DOCTYPE header information must include a valid URL syntax in order to avoid parser errors.

When editing or creating XML deployment files, it is critical to include the correct DOCTYPE header for each deployment file. In particular, using an incorrect PUBLIC element within the DOCTYPE header can result in parser errors that may be difficult to diagnose.

The header refers to the location and version of the Document Type Definition (DTD) file for the deployment descriptor. Although this header references an external URL at java.sun.com, WebLogic Server contains its own copy of the DTD file, so your host server need not have access to the Internet. However, you must still include this <!DOCTYPE...> element in your weblogic-ejb-jar.xml and weblogic-cmp-jar.xml files, and have them reference the external URL because the version of the DTD contained in this element is used to identify the version of this deployment descriptor.

XML files with incorrect header information may yield error messages similar to the following, when used with a tool that parses the XML (such as appc):

SAXException: This document may not have the identifier `identifier_name'

where identifier_name generally includes the invalid text from the PUBLIC element.

The correct text for the PUBLIC elements for the WebLogic-Server-specific weblogic-ejb-jar.xml file is listed, by WebLogic Server release, in Table A-1.

Table A-1 PUBLIC Elements of weblogic-ejb-jar.xml

WebLogic Server ReleaseXML FilePUBLIC Element String

8.1.x

weblogic-ejb-jar.xml

'-//BEA Systems, Inc.//DTD WebLogic 8.1.0 EJB//EN' 'http://www.bea.com/servers/wls810/dtd/weblogic-ejb-jar.dtd'

7.0.x

weblogic-ejb-jar.xml

'-//BEA Systems, Inc.//DTD WebLogic 7.0.0 EJB//EN' 'http://www.bea.com/servers/wls700/dtd/weblogic-ejb-jar.dtd'

6.1.x

and

6.0.x

weblogic-ejb-jar.xml

'-//BEA Systems, Inc.//DTD WebLogic 6.0.0 EJB//EN' 'http://www.bea.com/servers/wls600/dtd/weblogic-ejb-jar.dtd'

5.1.0

weblogic-ejb-jar.xml

'-//BEA Systems, Inc.//DTD WebLogic 5.1.0 EJB//EN'

'http://www.bea.com/servers/wls510/dtd/weblogic-ejb-jar.dtd'


The correct text for the PUBLIC elements for the WebLogic-Server-specific weblogic-cmp-jar.xml file is listed, by WebLogic Server release, in Table A-2.

Table A-2 PUBLIC Elements of weblogic-cmp-jar.xml

WebLogic Server ReleaseXML FilePUBLIC Element String

8.1.x

weblogic-cmp-jar.xml

'-// BEA Systems, Inc.//DTD WebLogic 8.1.0 EJB RDBMS Persistence//EN' 'http://www.bea.com/servers/wls810/dtd/weblogic-rdbms20-persistence-810.dtd'

7.0.x

weblogic-cmp-jar.xml

'-// BEA Systems, Inc.//DTD WebLogic 7.0.0 EJB RDBMS Persistence//EN' 'http://www.bea.com/servers/wls700/dtd/weblogic-rdbms20-persistence-700.dtd'

6.1.x

and

6.0.x

weblogic-cmp-jar.xml

'-// BEA Systems, Inc.//DTD WebLogic 6.0.0 EJB RDBMS Persistence//EN' 'http://www.bea.com/servers/wls600/dtd/weblogic-rdbms20-persistence-600.dtd'


See Appendix A, "Deployment Descriptor Schema and Document Type Definitions Reference" for more information on the weblogic-cmp-jar.xml file.

The correct text for the PUBLIC elements for the Sun-Microsystems-specific ejb-jar.xml file is listed, by Enterprise JavaBeans version, in Table A-3.

Table A-3 PUBLIC Elements of ejb-jar.xml

EJB VersionXML FilePUBLIC Element String

2.0

ejb-jar.xml

'-//Sun Microsystems, Inc.//DTD Enterprise JavaBeans 2.0//EN'

'http://java.sun.com/dtd/ejb-jar_2_0.dtd'

1.1

ejb-jar.xml

'-//Sun Microsystems, Inc.//DTD Enterprise JavaBeans 1.1//EN'

'http://www.java.sun.com/j2ee/dtds/ejb-jar_1_1.dtd'


PKqn<<PK;wEOEBPS/overview.htm*I Introduction and Roadmap

1 Introduction and Roadmap

This section describes the contents and organization of this guide—Programming Enterprise JavaBeans for Oracle WebLogic Server.

Document Scope and Audience

This document is a resource for software developers who develop applications that include WebLogic Server Enterprise JavaBeans (EJBs). It also contains information that is useful for business analysts and system architects who are evaluating WebLogic Server or considering the use of WebLogic Server EJBs for a particular application.

The topics in this document are relevant during the design and development phases of a software project. The document also includes topics that are useful in solving application problems that are discovered during test and pre-production phases of a project.

This document does not address production phase administration, monitoring, or performance tuning. For links to WebLogic Server documentation and resources for these topics, see Related Documentation.

It is assumed that the reader is familiar with Java EE and EJB concepts. This document emphasizes the value-added features provided by WebLogic Server EJBs and key information about how to use WebLogic Server features and facilities to get an EJB application up and running.

Guide to this Document

Related Documentation

This document contains EJB-specific design and development information.

For comprehensive guidelines for developing, deploying, and monitoring WebLogic Server applications, see the following documents:

Samples and Tutorials for the EJB Developer

In addition to this document, Oracle provides a variety of code samples and tutorials for EJB developers. The examples and tutorials illustrate WebLogic Server EJBs in action, and provide practical instructions on how to perform key EJB development tasks.

Oracle recommends that you run some or all of the EJB examples before developing your own EJBs.

Avitek Medical Records Application (MedRec) and Tutorials

MedRec is an end-to-end sample Java EE application shipped with WebLogic Server that simulates an independent, centralized medical record management system. The MedRec application provides a framework for patients, doctors, and administrators to manage patient data using a variety of different clients.

MedRec demonstrates WebLogic Server and Java EE features, and highlights Oracle-recommended best practices. MedRec is included in the WebLogic Server distribution, and can be accessed from the Start menu on Windows machines. For Linux and other platforms, you can start MedRec from the WL_HOME\samples\domains\medrec directory, where WL_HOME is the top-level installation directory for WebLogic Platform.

MedRec includes a service tier comprised primarily of EJBs that work together to process requests from Web applications, Web services, and workflow applications, and future client applications. The application includes message-driven, stateless session, stateful session, and entity EJBs.

As companion documentation to the MedRec application, Oracle provides tutorials that provide step-by-step procedures for key development tasks, including EJB-specific tasks, such as:

  • Using EJBGen to Generate EJB deployment descriptors

  • Exposing a stateless Session EJB as a Web service

  • Securing EJB resources using the Administration Console

EJB Examples in the WebLogic Server Distribution

WebLogic Server optionally installs API code examples in WL_HOME\samples\server\examples\src\examples\ejb, where WL_HOME is the top-level directory of your WebLogic Server installation. You can start the examples server, and obtain information about the samples and how to run them from the WebLogic Server Start menu.

New and Changed Features in This Release

For a comprehensive listing of the new WebLogic Server features introduced in this release, see "What's New in WebLogic Server" in What's New in Oracle WebLogic Server.

PK **PK;wEOEBPS/message_beans.htmD Message-Driven EJBs

7 Message-Driven EJBs

Oracle Fusion Middleware Programming Message-Driven Beans for Oracle WebLogic Server describes the message-driven bean (MDB) life cycle, design considerations, and instructions for key implementation tasks. For a description of the overall EJB development process, see Implementing Enterprise JavaBeans.

PKIDPK;wEOEBPS/cmp_jar_ref.htm weblogic-cmp-jar.xml Deployment Descriptor Reference

C weblogic-cmp-jar.xml Deployment Descriptor Reference

The following sections describe the EJB 2.1 elements in the weblogic-cmp-jar.xml file, the WebLogic-specific XML Schema-based (XSD) deployment descriptor file. Use these definitions to create the WebLogic-specific weblogic-cmp-jar.xml file that is part of your EJB deployment. Use this deployment descriptor file to specify container-managed-persistence (CMP) behavior.

In this release of WebLogic Server, weblogic-cmp-jar.xml is XML Schema-based (XSD). In prior releases, weblogic-cmp-jar.xml was Document Type Definition-based (DTD). For backward compatibility, this release of WebLogic Server supports XSD- or DTD-based EJB descriptors. In this release of WebLogic Server, the EJB container still supports all older DTD-based descriptors; you can deploy applications that use DTD-based descriptors in this release of WebLogic Server without modifying the descriptors.

For information on the EJB 1.1 deployment descriptor elements see Appendix F, "Important Information for EJB 1.1 Users."

For information on:

EJB 1.1 deployment descriptor elements, see Appendix F, "Important Information for EJB 1.1 Users."

2.1 weblogic-cmp-jar.xml Deployment Descriptor File Structure

The weblogic-cmp-jar.xml file defines deployment descriptors for entity EJBs that use WebLogic Server RDBMS-based persistence services. The EJB container uses a version of weblogic-cmp-jar.xml that is different from the XML shipped with pre-9.0 releases of WebLogic Server.

You can continue to use the earlier weblogic-cmp-jar.xml DTD beans that you deploy to this release of WebLogic Server; likewise, you can continue to use the weblogic-cmp-jar.xml DTD that was supported in WebLogic Server 8.1. Though deployment descriptors are XSD-based beginning with WebLogic Server 9.0, for backward compatibility, WebLogic Server continues to support DTD-based descriptors. However, if you want to use any of the CMP 2.1 features, you must use the XSD described below.

Oracle recommends that you run DDConverter to convert EJB deployment descriptors from pre-9.0 releases of WebLogic Server to conform to the current release of WebLogic Server. DDConverter converts your DTD-based EJB deployment descriptors from pre-9.0 releases of WebLogic Server to XSD-based descriptors supported in this release.


Note:

Oracle recommends that you always convert descriptors when migrating applications to a new WebLogic Server release.

The top-level element of the WebLogic Server weblogic-cmp-jar.xml consists of a weblogic-rdbms-jar element:

weblogic-rdbms-jar
    weblogic-rdbms-bean
    ejb-name
    data-source-jndi-name
    table-map
    field-group
    relationship-caching
    sql-shape
    weblogic-query
    delay-database-insert-until
    use-select-for-update
    lock-order
    instance-lock-order
    automatic-key-generation
    check-exists-on-method
    cluster-invalidation-disabled

weblogic-rdbms-relation
    relation-name
    table-name
     weblogic-relationship-role
order-database-operations
enable-batch-operations
create-default-dbms-tables
validate-db-schema-with
database-type
default-dbms-tables-ddl

compatibility
    serialize-byte-array-to-oracle-blob
    serialize-char-array-to-bytes
    allow-readonly-create-and-remove
    disable-string-trimming

2.1 weblogic-cmp-jar.xml Deployment Descriptor Elements

This list of the elements in weblogic-cmp-jar.xml includes all elements that are supported in WebLogic Server.

allow-readonly-create-and-remove

Range of values: true | false

Default value: false

Parent elements:

weblogic-rdbms-jar
  compatibility

Function

This element, introduced in WebLogic Server 8.1 SP02, is a backward compatibility flag. It is used to enable create and remove operations for an EJB that uses ReadOnly concurrency.

Prior to WebLogic Server 8.1 SP2, these operations were allowed, although they had no transactional meaning. They have been disallowed so that more efficient code can be generated for ReadOnly beans, and because using them is a bad practice.

Example

<compatibility> 
    <allow-readonly-create-and-remove>
        true
    </allow-readonly-create-and-remove>
</compatibility>

automatic-key-generation

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-rdbms-bean

Function

The automatic-key-generation element specifies how primary keys will be automatically generated. For more information about this feature, see Automatically Generating Primary Keys.

Example

The following code samples show the automatic-key-generation element for different primary key generation methods. For supported generation methods, see generator-type.

Example C-1 automatic-key-generation With generator-type=Oracle

<automatic-key-generation>
    <generator-type>Oracle</generator-type>
    <generator-name>test_sequence</generator-name>
    <key-cache-size>10</key-cache-size>
</automatic-key-generation>

Example C-2 automatic-key-generation With generator-type=SQL-SERVER

<automatic-key-generation>
    <generator-type>SQL-SERVER</generator-type>
</automatic-key-generation>

Example C-3 automatic-key-generation With generator-type=NamedSequenceTable

<automatic-key-generation>
    <generator-type>NamedSequenceTable</generator-type>
    <generator-name>MY_SEQUENCE_TABLE_NAME</generator-name>
    <key-cache-size>100</key-cache-size>
</automatic-key-generation>

caching-element

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-rdbms-jar
  weblogic-rdbms-bean
    relationship-caching

Function

Specifies the cmr-field and the group-name in the related bean. If group-name is not specified, the default group-name (load all fields) is used. For more information, see group-name.

caching-element can contain nested caching elements, as in the example shown in relationship-caching.

For information about relationship caching, see Relationship Caching.

Example

See relationship-caching:

caching-name

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-rdbms-jar
  weblogic-rdbms-bean
    relationship-caching

Function

The caching-name element specifies the name of a relationship cache. For more information about relationship caching, see Relationship Caching.

Example

See relationship-caching.

check-exists-on-method

Range of values: True | False

Default value: True

Parent elements:

weblogic-rdbms-bean

Function

By default, the EJB container checks that a container-managed persistence (CMP) entity bean exists before any business method invoked on the bean completes. This means the container notifies an application as soon as any business method is invoked on a container-managed entity bean that has been removed.

To specify that the EJB container wait for transaction completion to perform the existence check, set check-exists-on-method to False. This results in high performance and still provides a sufficient level of checking for most applications.

Example

The following example specifies that WebLogic Server notify the application that a business method has been invoked on a CMP entity bean that has been removed.

<check-exists-on-method>True</check-exists-on-method>

cluster-invalidation-disabled

Range of values: true | false

Default value: false

Parent elements:

weblogic-rdbms-bean

Function

This flag, introduced in WebLogic Server 9.0, is used to disable or enable invalidation of an EJB that uses Optimistic or ReadOnly concurrency when the EJB is updated by a member of a cluster to which it is deployed. For more information, see Invalidation Options for Optimistic Concurrency in Clusters.

Example

<cluster-invalidation-disabled>true</cluster-invalidation-disabled>

cmp-field

Range of values: Valid name of field in the bean. Field must have matching cmp-entry in ejb-jar.xml. Field name is case-sensitive.

Default value: n/a

Parent elements:

weblogic-rdbms-bean
  field-map

and

weblogic-rdbms-relation
  field-group

Function

This name specifies the mapped field in the bean instance which should be populated with information from the database.

Example

See field-map.

cmr-field

Range of values: Valid name of field in the bean. Field must have matching cmr-field entry in ejb-jar.xml

Default value: n/a

Parent elements:

weblogic-rdbms-relation
  field-group

and

relationship-caching
  caching-element

Function

Specifies the name of a container-managed relationship field.

Example

<cmr-field>stock options</cmr-field>

column-map

Range of values: n/a

Default value: n/a

Parent elements:

<weblogic-rdbms-relation>
  <weblogic-relationship-role>
    <relationship-role-map>

Function

This element represents the mapping of a foreign key column in one table in the database to a corresponding primary key. The two columns may or may not be in the same table. The tables to which the columns belong are implicit from the context in which the column-map element appears in the deployment descriptor.

Example

The following is an example of the column-map element:


Note:

You do not need to specify the key-column element if the foreign-key-column refers to a remote bean.

<column-map>
    <foreign-key-column>account-id</foreign-key-column>
    <key-column>id</key-column>
</column-map>

compatibility

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-rdbms-jar

Function

The <compatibility> element, introduced in WebLogic Server 8.1 SP02, contains elements that specify compatibility flags for all of the cmp beans described in the descriptor file.

Example

<compatibility> 
    <serialize-byte-array-to-oracle-blob>...</serialize-byte-array-to-oracle-blob>
    <serialize-char-array-to-bytes>...</serialize-char-array-to-bytes>
    <allow-readonly-create-and-remove>...</allow-readonly-create-and-remove>
    <disable-string-trimming>...</disable-string-trimming>
</compatibility>

create-default-dbms-table

Range of values: Disabled | CreateOnly | DropAndCreate | DropAndCreateAlways | AlterOrCreate

Default value: Disabled

Parent elements:

weblogic-rdbms-jar

Function

The create-default-dbms-table element performs two functions:

  • It determines whether or how WebLogic Server automatically creates a default table based on the descriptions in the deployment files and the bean class, when underlying table schema have changed.

  • It determines whether or how WebLogic Server automatically creates an Oracle database SEQUENCE.

Use this element only for convenience during development phases. This is because the table schema in the DBMS CREATE statement used are the EJB container's best approximation of the definition. A production environment typically requires more precise schema definition.

Automatic Table Creation

The following table describes how WebLogic Server handles automatic table creation, based on the value of create-default-dbms-tables.

Table C-1 Automatic Table Creation

Setting <create-default-dbms-tables> to this value...Results in this behavior with respect to automatic table creation...

Disabled

The EJB container takes no action with respect to automatic table creation. This is the default value.

CreateOnly

The EJB container automatically generates the table upon detecting changed schema.

The container attempts to create the table based on information found in the deployment files and in the bean class. If table creation fails, a 'Table Not Found' error is thrown, and the user must create the table manually.

DropAndCreate

The EJB container automatically generates the table upon detecting changed schema.

The container drops and recreates the table during deployment only if columns have changed. The container does not save data.

You must ensure that the column type and cmp-field types are compatible. The EJB container does not attempt to ensure the column type and cmp-field types are compatible.

DropAndCreateAlways

The EJB container automatically generates the table upon detecting changed schema.

The container drops and creates the table during deployment whether or not columns have changed. The container does not save the data.

AlterOrCreate

The EJB container automatically generates the table upon detecting changed schema.

The container creates the table if it does not yet exist. If the table does exist, the container alters the table schema. Table data is saved.

Note: Do not choose this setting if a new column is specified as a primary key or if a column with null values is specified as the new primary key column.


If TABLE CREATION fails, the server throws a Table Not Found error and the table must be created manually.

See Automatic Table Creation (Development Only).

Automatic Oracle Database SEQUENCE Generation


Note:

Automatic Oracle database SEQUENCE generation works only with servers running in development mode.

The following table describes how WebLogic Server handles automatic SEQUENCE generation, based on the value of create-default-dbms-tables.

Table C-2 Automatic Oracle Database SEQUENCE Generation

Setting <create-default-dbms-tables> to this value...Results in this behavior...

Disabled

The EJB container takes no action with respect to SEQUENCE generation. This is the default value.

CreateOnly

The EJB container creates a SEQUENCE, and constructs its name by appending "_WL" to the value of the generator-name element.

DropAndCreate

The EJB container creates a SEQUENCE, and constructs its name by appending "_WL" to the value of the generator-name element.

If the SEQUENCE's increment value does not match the value of the key-cache-size element, the container alters the increment value to match the value of key-cache-size.

DropAndCreateAlways

The EJB container creates a SEQUENCE, and constructs its name by appending "_WL" to the value of the generator-name element.

If the SEQUENCE's increment value does not match the value of the key-cache-size element, the container alters the increment value to match the value of key-cache-size.

AlterOrCreate



The EJB container creates a SEQUENCE, and constructs its name by appending "_WL" to the value of the generator-name element.

If the SEQUENCE's increment value does not match the value of the key-cache-size element, the container alters the increment value to match the value of key-cache-size.


For more information on automatic generation of an Oracle database SEQUENCE, see Support for Oracle Database SEQUENCE.

Example

The following example specifies the create-default-dbms-tables element.

<create-default-dbms-tables>CreateOnly</create-default-dbms-tables>

database-specific-sql

Range of values: n/a

Default value: n/a

Requirements: database-type must be specified.

Parent elements:

weblogic-rdbms-jar
  weblogic-rdbms-bean
    weblogic-query
      sql-query

Function

The database-specific-sql element specifies a database-specific SQL statement.

Example

<database-specific-sql>
    <database-type>SQLServer</database-type>
    <sql>SELECT name, phone, location, testid FROM medrecappPharmacyBeanTable WHERE
         testid = ?1 AND SUBSTRING(testid, 1,5) = 'local' ORDER BY name
    </sql>
</database-specific-sql>

database-type

Range of values: DB2 | Informix | MySQL | Oracle | SQLServer | SQLServer2000 | Sybase

Default value: n/a

Parent elements:

weblogic-rdbms-jar

and

weblogic-rdbms-jar
  weblogic-rdbms-bean
    weblogic-quer
      sql-query
        database-specific-sql

Function

The database-type element specifies the database used as the underlying WebLogic Server dbms or the dbms against which to execute a vendor-specific SQL statement. If you specify database-type in the weblogic-rdbms-jar element, the database you specify applies to the entire weblogic-rdbms-jar deployment descriptor file unless it is overridden in a database-specific-sql element by another database-type element.

Example

<database-type>Oracle</database-type>

data-source-jndi-name

Range of values: Valid WebLogic Server JDBC data source name

Default value: n/a

Parent elements:

weblogic-rdbms-bean

Function

Specifies the JDBC data source name to be used for database connectivity for this bean. For more information on data sources, see Programming JDBC for Oracle WebLogic Server.


Note:

Prior to WebLogic Server 9.0, this element was data-source-name.

Example

See table-name.

db-cascade-delete

Range of values: n/a

Default value: By default, database cascade delete is not used. The EJB container performs cascade deletes by issuing an individual SQL DELETE.

Parent elements:

weblogic-rdbms-bean
  weblogic-relationship-role

Function

Allows an application to take advantage of a database's built-in support for cascade delete, and possibly improve performance. This functionality is supported only for:

  • Oracle databases

  • One-to-one or one-to-many relationships.

If db-cascade-delete is enabled in weblogic-cmp-rdbms-jar.xml, you must

  • Enable cascade-delete in ejb-jar.xml

  • Enable cascade delete in the database table definition.


    Note:

    If db-cascade-delete is not specified, do not enable the database's cascade delete functionality, as this will produce incorrect results.

Setting up Oracle Database for Cascade Delete

The following Oracle database table definition will cause deletion all of the emp rows if the owning dept is deleted in the database.

CREATE TABLE dept
(deptno   NUMBER(2) CONSTRAINT pk_dept PRIMARY KEY,
dname    VARCHAR2(9) );
CREATE TABLE emp
(empno    NUMBER(4) PRIMARY KEY,
ename    VARCHAR2(10),
deptno   NUMBER(2)   CONSTRAINT fk_deptno
REFERENCES dept(deptno)
ON DELETE CASCADE );

Example

<weblogic-relationship-role>
    <db-cascade-delete/>
</weblogic-relationship-role>

dbms-column

Range of values: Valid database column

Default value: n/a

Parent elements:

weblogic-rdbms-bean
  field-map

Function

The name of the database column to which the field should be mapped.


Note:

dbms-column is case maintaining, although not all database are case sensitive.

Example

See field-map.

dbms-column-type

Range of values: Blob | Clob | LongString | SybaseBinary

Default value: n/a

Requirements: To specify Blob or Clob in this element, you must also set dbms-default-value to Oracle or DB2 databases.

Parent elements:

weblogic-rdbms-bean
  field-map

Function

Specifies the type of the cmp-field. Maps the current field to a Blob or Clob in an Oracle or DB2 database or to a LongString or SybaseBinary in a Sybase database.

  • Blob—maps the field to an Oracle or DB2 database Blob.

  • Clob—maps the field to an Oracle or DB2 database Clob.

  • LongString—tells the container to use setCharacterStream to write String data into the database. Some JDBC drivers have problems writing more than 4K of data using setString.

  • SybaseBinary—tells the container to use setBytes to write bytes into the binary column, because setBinaryStream does not work with SybaseXADriver.

Example

<field-map>
    <cmp-field>photo</cmp-field>
    <dbms-column>PICTURE</dbms-column>
    <dbms_column-type>OracleBlob</dbms-column-type>
</field-map>

dbms-default-value

Range of values: DB2 | Informix| MySQL | Oracle | SQLServer | SQLServer2000 | Sybase

Default value:

Parent elements:

weblogic-rdbms-bean
  field-map

Function

Specifies the database used as the default underlying dbms. This value can be overridden by the database-type element.

Example

<dbms-default-value>Oracle</dbms-default-value>

default-dbms-tables-ddl

Range of values: Valid file name

Default value:

Parent elements:

weblogic-rdbms-jar

Function

Specifies the DDL file name to which the EJB container writes the table creation scripts.

delay-database-insert-until

Range of values: ejbCreate | ejbPostCreate

Default value: ejbPostCreate

Requirememts:

Parent elements:

weblogic-rdbms-bean

Function

Specifies when a new CMP bean is inserted into the database. The allowable values cause the following behavior:

  • ejbCreate - perform database insert immediately after ejbCreate. This setting yields better performance than ejbCreate by avoiding an unnecessary store operation.

  • ejbPostCreate - perform insert immediately after ejbPostCreate.

This element has an effect only when order-database-operations is False. By default, order-database-operations is true, which causes new beans to be inserted at the transaction commit time.

Delaying the database insert until after ejbPostCreate is required when a cmr-field is mapped to a foreign-key column that does not allow null values. In this case, the cmr-field must be set to a non-null value in ejbPostCreate before the bean is inserted into the database.

For maximum flexibility, avoid creating related beans in your ejbPostCreate method. If ejbPostCreate creates related beans, and database constraints prevent related beans from referring to a bean that has not yet been created, it is not possible to perform a database insert until after the method completion.


Note:

cmr-fields may not be set during ejbCreate, before the primary key of the bean is known.

Example

<delay-database-insert-until>ejbPostCreate</delay-database-insert-until>

description

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-rdbms-jar
  weblogic-rdbms-bean
    weblogic-query

or

weblogic-rdbms-jar
  weblogic-rdbms-bean
    sql-shape

Function

The description element provides text that describes the parent element.

Example

<description>Contains a description of parent element</description>

disable-string-trimming

Range of values: True | False

Default value: False

Parent elements:

compatibility

Function

This element, introduced in WebLogic Server 9.0, is a compatibility flag. It is used to specify whether a cmp-field of type string[] should be trimmed. Set this flag to True to disable string trimming. For more information on string trimming, see String-Valued CMP Field Trimming and Disabling String Trimming.

Example

<compatibility>
    <disable-string-trimming>True</disable-string-trimming>
</compatibility>

ejb-name

Range of values: Must match the ejb-name of a cmp entity bean defined in the ejb-jar.xml

Default value: n/a

Parent elements:

weblogic-rdbms-bean

Function

The name that specifies an EJB as defined in the ejb-cmp-rdbms.xml. This name must match the ejb-name of a cmp entity bean contained in the ejb-jar.xml.

Example

See table-name.

ejb-ql-query

Range of values:

Default value:

Parent elements:

weblogic-rdbms-jar
  weblogic-rdbms-bean
    weblogic-query

Function

The ejb-ql-query element specifies an EJB-QL query. You should only specify EJB-QL queries that implement EJB finders or contain WebLogic-specific extensions in the weblogic-cmp-jar.xml deployment descriptor; specify queries that use only standard EJB-QL features in the ejb-jar.xml deployment descriptor.

Example

See weblogic-query.

enable-batch-operations

Range of values: True | False

Default value: True

Parent elements:

weblogic-rdbms-jar

Function

This element, introduced in WebLogic Server 8.1, controls whether or not the EJB container allows batch database operations, including batch inserts, batch updates, and batch deletes.

If this element is set to True, the EJB delays database operations in a transaction until commit time.

Example

The following XML sample demonstrates use of the enable-batch-operations element:

<enable-batch-operations>True</enable-batch-operations>

enable-query-caching

Range of values: True | False

Default value: True

Parent elements:

weblogic-rdbms-jar
  weblogic-rdbms-bean
    weblogic-query

or

weblogic-rdbms-jar
  weblogic-rdbms-relation

Function

This element, introduced in WebLogic Server 9.0, controls whether read-only entity EJBs can be cached at the query level. Caching read-only entity EJBs at the query level improves performance because it enables the EJBs to be accessed in cache by any finder, thereby avoiding the need to access the database. If you set this value to True, you can specify the maximum number of queries to cache at the application or bean level. To specify the maximum number of queries to cache, set max-queries-in-cache in the weblogic-ejb-jar.xml deployment descriptor. For information, see max-queries-in-cache.

Example

The following XML sample demonstrates use of the enable-query-caching element:

<enable-query-caching>True</enable-query-caching>

field-group

Range of values: n/a

Default value: A special group named default is used for finders and relationships that have no field-group specified. The default group contains all of a bean's cmp-fields, but none of its cmr-fields.

Parent elements:

weblogic-rdbms-relation

Function

The field-group element represents a subset of the cmp-fields and cmr-fields of a bean. Related fields in a bean can be put into groups that are faulted into memory together as a unit. A group can be associated with a finder or relationship, so that when a bean is loaded as the result of executing a finder or following a relationship, only the fields specified in the group are loaded.

A field may belong to multiple groups. In this case, the getXXX method for the field faults in the first group that contains the field.

Example

The field-group element can contain the elements shown here:

<weblogic-rdbms-bean>
    <ejb-name>XXXBean</ejb-name>
    <field-group>
        <group-name>medical-data</group-name>
        <cmp-field>insurance</cmp-field>
        <cmr-field>doctors</cmr-fields>
    </field-group>
</weblogic-rdbms-bean>

field-map

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-rdbms-bean

Function

The field-map element represents a mapping between a particular column in a database and a cmp-field in the bean instance.

The optional group-name element specifies a field group that is to be loaded when the getXXX method for the cmp-field is called and the EJB container needs to read the value from the DBMS because it is not in memory. If group-name is omitted, the default group, which contains all cmp-fields, is used when the cmp-field is not explicitly listed in any field groups, otherwise a field group that contains the cmp-field is chosen. Thus, developers should specify a group-name if the cmp-field is listed in multiple field groups or the container will pick one of the groups arbitrarily.

The dbms-column-type element is optional.

Example

The field-map element can contain the elements shown here:

<field-map>
    <cmp-field>....</cmp-field>
    <dbms-column>...</dbms-column>
    <dbms-column-type>...</dbms-column-type>
    <group-name>...</group name>
</field-map>

finders-return-nulls

Range of values: True | False

Default value: n/a

Parent elements:

weblogic-rdbms-jar
  compatibility
    weblogic-query

Function

This element, introduced in WebLogic Server 9.0, is a compatibility flag. It is used to specify whether finders can return null results.

Example

<compatibility>
    <finders-return-nulls>True</finders-return-value>
</compatibility>

foreign-key-column

Range of values: Valid foreign key database column name

Default value: n/a

Parent elements:

weblogic-rdbms-bean
  column-map

Function

The foreign-key-column element represents a column of a foreign key in the database.

Example

See column-map.

foreign-key-table

Range of values: Valid database table name

Default value: n/a

Parent elements:

weblogic-rdbms-jar
  weblogic-rdbms-relation
    weblogic-relationship-role
      relationship-role-map

Function

The foreign-key-table element specifies the name of a DBMS table that contains a foreign key.

generator-name

Range of values:

Default value:

Parent elements:

weblogic-rdbms-bean
  automatic-key-generation

Function

The generator-name element is used to specify the name of the primary key generator.

  • If the generator-type element is Oracle, and WebLogic Server is running in development mode, then the EJB container constructs the Oracle database SEQUENCE name by appending "_WL" to the generator-name as part of the container's automatic SEQUENCE generation feature.

    For more information on automatic Oracle database SEQUENCE generation, see Support for Oracle Database SEQUENCE.

  • If the generator-type element is Oracle, and WebLogic Server is running in production mode, then the EJB container sets the name of the Oracle database SEQUENCE to the value of generator-name.

  • If the generator-type element is NamedSequenceTable, then the generator-name element would be the name of the SEQUENCE_TABLE to be used.

generator-type

Range of values: Identity | Sequence | SequenceTable

Default value:

Parent elements:

weblogic-rdbms-bean
  automatic-key-generation

Function

The generator-type element specifies the primary key generation method to use.


Note:

You must set the database-type element when using automatic-key-generation.

In addition, generator-type is used in conjunction with automatic Oracle database SEQUENCE generation. See Support for Oracle Database SEQUENCE.

The following databases are supported for each generator-type:

  • Identity: Oracle databases are not supported.

  • Sequence: Oracle, DB2, and Informix (version 9.2 and greater) databases are supported.

  • SequenceTable: All databases are supported.

group-name

Range of values: n/a

Default value:

field-group

and

caching-element

and

weblogic-query

and

field-map

and

weblogic-relationship-role

Parent elements:

weblogic-rdbms-relation
  field-group

Function

Specifies the name of a field group.

Example

See field-group.

include-result-cache-hint

Range of values: True | False

Default value: False for beans that use optimistic concurrency. True for beans that use other concurrency types.

Parent elements:

weblogic-rdbms-jar
  weblogic-rdbms-bean
    relationship-caching

Function

When configuring a EJB CMP queries, specifies whether RESULT_CACHE hints are added to the generated SQL. If this element is set to True, the following hint is added to the generated SQL for the query:

/*+ RESULT_CACHE */

include-updates

Range of values: True | False

Default value: False for beans that use optimistic concurrency. True for beans that use other concurrency types.

Parent elements:

weblogic-rdbms-bean
  weblogic-query

Function

Specifies whether updates made during the current transaction must be reflected in the result of a query. If this element is set to True, the container will flush all changes made by the current transaction to disk before executing the query. A value of False provides best performance.

Example

<weblogic-query>
    <query-method>
    <method-name>findBigAccounts</method-name>
    <method-params>
        <method-param>double</method-param>
    </method-params>
    </query-method>
    <ejb-ql-query>
        <weblogic-ql>WHERE BALANCE>10000 ORDER BY NAME</weblogic-ql>
    </ejb-ql-query>
    <include-updates>True</include-updates>
</weblogic-query>

instance-lock-order

Range of values: AccessOrder | ValueOrder

Default value: AccessOrder

Parent elements:

weblogic-rdbms-bean

Function

Specifies a locking or processing order for instances of a particular EJB. This element can be used to prevent deadlocks in an application that would otherwise experience deadlocks. instance-lock-order is used whenever database operations (update, for example) that apply to multiple instances of the same EJB are performed by the container. It specifies an order for operations that can cause a database lock to be acquired for a bean instance.

For example, instance-lock-order could be used to specify the order in which the EJB container calls ejbStore for instances of a particular EJB that uses database concurrency; ejbStore may acquire an exclusive lock when a database update is done. instance-lock-order also controls the order in which beans using optimistic concurrency are locked when optimistic checking is performed.

  • AccessOrder—The container will process beans so that locks are acquired (or upgraded) in the order in which the application originally accessed the beans during the transaction. This is the recommended value when all transactions in the system access instances of the bean, and ultimately rows in a database table, in the same order.

  • ValueOrder—Beans are processed in order based on the value of their primary key. ValueOrder should be specified to avoid deadlocks when concurrent transactions access instances of the same EJB in different orders.


    Note:

    The EJB's primary key class is not required to implement the java.lang.Comparable interface when ValueOrder is specified, although this will result in a total ordering. Beans are ordered partially using the hash code value of the primary key when the primary key does not implement java.lang.Comparable.

Example

<instance-lock-order>ValueOrder</instance-lock-order>

key-cache-size

Range of values:

Default value: 1

Parent elements:

weblogic-rdbms-bean
  automatic-key-generation

Function

Specifies the optional size of the primary key cache available in the automatic primary key generation feature. In addition, the EJB container uses this value to calculate the increment value for an Oracle database SEQUENCE when automatic SEQUENCE generation is enabled. See Support for Oracle Database SEQUENCE.

If generator-type is:

  • Oraclekey-cache-size must match the Oracle database SEQUENCE INCREMENT value. If there is a mismatch between this value and the Oracle database SEQUENCE INCREMENT value, then there will likely be duplicate key problems.

  • NamedSequenceTablekey-cache-size specifies how many keys the container will fetch in a single DBMS call.

  • SQLServer—key-cache-size is ignored.

key-column

Range of values: Valid primary key column name

Default value: n/a

Parent elements:

weblogic-rdbms-bean
  column-map

Function

The key-column element represents a column of a primary key in the database.

Example

See column-map.

lock-order

Range of values: All positive integers

Default value: 0

Parent elements:

weblogic-rdbms-bean

Function

Use this flag to specify the database locking order of an entity bean when a transaction involves multiple beans and exclusive concurrency. The bean with the lowest number is locked first.

This flag should only be used to prevent a deadlock situation and, currently, only applies when a transaction performs cascade deletes.

Example

An example of the lock-order element is:

<lock-order>1</lock-order>
    <!ELEMENT lock-order (PCDATA)>

max-elements

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-rdbms-bean
  weblogic-query

Function

max-elements specifies the maximum number of elements that should be returned by a multi-valued query. This element is similar to the maxRows feature in JDBC.

Example

An example of the max-elements element is shown here:

<max-elements>100</max-elements>
    <!ELEMENT max-element (PCDATA)>

method-name

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-rdbms-bean
  query-method

Function

The method-name element specifies the name of a finder or ejbSelect method.


Note:

The '*' character cannot be used as a wildcard.

Example

See weblogic-query.

method-param

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-rdbms-bean
  method-params

Function

The method-param element contains the fully qualified Java type name of a method parameter.

Example

<method-param>java.lang.String</method-param>

method-params

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-rdbms-bean
  query-method

Function

The method-params element contains an ordered list of the fully-qualified Java type names of the method parameters.

Example

See weblogic-query.

optimistic-column

Range of values: Valid database column name

Default value: n/a

Parent elements:

weblogic-rdbms-bean
  table-map

Function

The optimistic-column element denotes a database column that contains a version or timestamp value used to implement optimistic concurrency. For more information on optimistic concurrency, see Choosing a Concurrency Strategy.


Note:

Although not all databases are case sensitive, this element is case maintaining.

Example

The following sample XML shows the use of the optimistic-column element.

<optimistic-column>ROW_VERSION</optimistic-column>

where ROW_VERSION is the name of a database column that contains the value used for concurrency checking.

order-database-operations

Range of values: True | False

Default value: True

Parent elements:

weblogic-rdbms-jar

Function

This element, introduced in WebLogic Server 8.1, determines whether the EJB container delays all database operations in a transaction until commit time, automatically sorts the database dependency between the operations, and sends these operations to the database in such a way to avoid any database constraint errors.

If enable-batch-operations is set to True, the container automatically sets order-database-operations to True. To turn off order-database-operations, set both order-database-operations and enable-batch-operations to False.

See also ejb-ql-query and delay-database-insert-until.

Example

<order-database-operations>True</order-database-operations>

pass-through-columns

Range of values: Any positive integer

Default value:

Parent elements:

weblogic-rdbms-bean
  sql-shape

Function

This element, introduced in WebLogic Server 9.0, specifies the number of aggregate columns that should be passed through to a SQL query result set without being mapped to anything.

Example

See sql-shape.

primary-key-table

Range of values: Valid database table name

Default value: n/a

Parent elements:

weblogic-rdbms-jar
  weblogic-rdbms-relation
    weblogic-relationship-role
      relationship-role-map

Function

The primary-key-table element specifies the name of a DBMS table that contains a primary key. For more information about primary keys, see Using Primary Keys.


Note:

Although not all databases are case sensitive, this element is case maintaining.

query-method

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-rdbms-bean

Function

Specifies the method that is associated with a weblogic-query. It also uses the same format as the ejb-jar.xml descriptor.

Example

See weblogic-query.

relation-name

Range of values: Must match the ejb-relation-name of an ejb-relation in the associated ejb-jar.xml deployment descriptor file. The ejb-relation-name is optional, but is required for each relationship defined in the associated ejb-jar.xml deployment descriptor file.

Default value: n/a

Parent elements:

weblogic-rdbms-relation

Function

The relation-name element specifies the name of a relation.

For more information about container-managed relationships, see Using Container-Managed Relationships (CMRs).

Example

An example of the relationship-name element is shown here:

<weblogic-rdbms-jar>
    <weblogic-rdbms-relation>
        <relation-name>stocks-holders</relation-name>
            <table-name>stocks</table-name>
    </weblogic-rdbms-relation>
</weblogic-rdbms-jar>

relationship-caching

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-rdbms-jar
  weblogic-rdbms-bean

Function

The relationship-caching element specifies relationship caching. For more information about relationship caching, see Relationship Caching.

Example

The relationship-caching element can contain the elements shown here:

<relationship-caching>
    <caching-name>cacheMoreBeans</caching-name>
    <caching-element>
        <cmr-field>accounts<</cmr-field>
        <group-name>acct_group</group-name>
        <caching-element>
            <cmr-field>address</cmr-field>
            <group-name>addr_group</group-name>
        </caching-element>
    </caching-element>
    <caching-element>
        <cmr-field>phone</cmr-field>
        <group-name>phone_group</group-name>
    </caching-element>
</relationship-caching>

relationship-role-map

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-rdbms-relation
  weblogic-relationship-role

Function

The relationship-role-map element specifies foreign key column to key column mapping for beans involved in a relationship.

A CMP bean that is involved in a relationship may be mapped to multiple DBMS tables (see the table-map element for more details). If the bean on the foreign key side of a one-to-one or one-to-many relationship is mapped to multiple tables, then the name of the table containing the foreign-key columns must be specified using the foreign-key-table element.

Conversely, if the bean on the primary key side of a one-to-one or one-to-many relationship or a bean participating in a m-n relationship is mapped to multiple tables, then the name of the table containing the primary key must be specified using the primary-key-table element.

If neither of the beans in a relationship is mapped to multiple tables, then the foreign-key-table and primary-key-table elements can be omitted because the tables being used are implicit.

For more information about container-managed relationships, see Using Container-Managed Relationships (CMRs).

Example

Mapping a Bean on Foreign Key Side of a Relationship to Multiple Tables

The bean on the foreign-key side of a one-to-one relationship, Fk_Bean, is mapped to multiple tables. The table that holds the foreign key columns must be specified in the foreign-key-table element.

Fk_Bean is mapped to two tables: Fk_BeanTable_1 and Fk_BeanTable_2. The foreign key columns for the relationship are located in table Fk_BeanTable_2. The foreign key columns are named Fk_column_1 and Fk_column_2. The bean on the primary key side, Pk_Bean, is mapped to a single table with primary key columns Pk_table_pkColumn_1 and Pk_table_pkColumn_2:

<relationship-role-map
    <foreign-key-table>Fk_BeanTable_2</foreign-key-table>
    <column-map>
        <foreign-key-column>Fk_column_1</foreign-key-column>
        <key-column>Pk_table_pkColumn_1</key-column>
    </column-map>
    <column-map>
        <foreign-key-column>Fk_column_2</foreign-key-column>
        <key-column>Pk_table_pkColumn_2</key-column>
    </column-map>
</relationship-role-map>

The foreign-key-table element must be specified so that the container can know which table contains the foreign key columns.

Mapping a Bean on Primary Key Side of a Relationship to Multiple Tables

The bean on the primary key side of a one-to-one relationship, Pk_bean, is mapped to multiple tables, but the bean on the foreign key side of the relationship, Fk_Bean, is mapped to one table, Fk_BeanTable. The foreign key columns are named Fk_column_1 and Fk_column_2.

Pk_bean is mapped to tables:

  • Pk_BeanTable_1 with primary key columns Pk_table1_pkColumn_1 and Pk_table1_pkColumn_2 and

  • Pk_BeanTable_2 with primary key columns Pk_table2_pkColumn_1 and Pk_table2_pkColumn_2.

<relationship-role-map>
    <primary-key-table>Pk_BeanTable_1</primary-key-table>
    <column-map>
        <foreign-key-column>Fk_column_1</foreign-key-column>
        <key-column>Pk_table1_pkColumn_1</key-column>
    </column-map>
    <column-map>
        <foreign-key-column>Fk_column_2</foreign-key-column>
        <key-column>Pk_table1_pkColumn_2</key-column>
    </column-map>
</relationship-role-map>

relationship-role-name

Range of values: Must match the ejb-relationship-role-name of an ejb-relationship-role in the associated ejb-jar.xml.

Default value: n/a

Parent elements:

weblogic-rdbms-relation
  weblogic-relationship-role

Function

The relationship-role-name element specifies the name of a relationship role.

For more information about container-managed relationships, see Using Container-Managed Relationships (CMRs).

Example

See the examples for weblogic-relationship-role.

serialize-byte-array-to-oracle-blob

Range of values: True | False

Default value: False

Parent elements:

weblogic-rdbms-jar
  compatibility

Function

This element, introduced in WebLogic Server 8.1 SP02, is a compatibility flag. It is used to specify whether a cmp-field of type byte[] mapped to a Blob in an Oracle database should be serialized. By default, the value of the tag is false, which means that the container will persist the byte[] directly and not serialize it.

In versions prior to WebLogic Server 8.1 SP02, the default behavior was to serialize a cmp-field of type byte[] mapped to a Blob in an Oracle database. To revert to the old behavior, set the value of serialize-byte-array-to-oracle-blob to true.

Example

<compatibility>
   <serialize-byte-array-to-oracle-blob>true</serialize-byte-array-to-oracle-blob>
</compatibility>

serialize-char-array-to-bytes

Range of values: True | False

Default value: False

Parent elements:

weblogic-rdbms-jar
  compatibility

Function

This element, introduced in WebLogic Server 9.0, is a compatibility flag. It is used to specify whether a cmp-field of type char[] mapped to a byte should be serialized. By default, the value of the tag is False, which causes the EJB container to persist the char[] directly and not serialize it; If you want the EJB container to serialize the char[], set this value to True.

Example

<compatibility>
    <serialize-char-array-to-bytes>true</serialize-char-array-to-bytes>
</compatibility>

sql

Range of values: Valid SQL

Default value: n/a

Requirements: To use database-specific SQL, you must specify the database against which to execute the SQL in the in database-type element.

Parent elements:

weblogic-rdbms-bean
  weblogic-query
    sql-query

and

weblogic-rdbms-bean
  weblogic-query
    sql-query
      database-specific-query

Function

The sql element contains a standard or database-specific SQL query. You should specify queries that use only standard EJB-QL language features in the ejb-jar.xml deployment descriptor. Specify queries that contain standard SQL, database-specific SQL, or WebLogic extensions to EJB-QL in the weblogic-cmp-jar.xml deployment descriptor.

Example

...
<weblogic-rdbms-bean>
    <weblogic-query>
        <sql-query>
            <sql>SELECT date_prescribed, dosage, drug, id, frequency,
                 instructions, pat_id, issuing_phys_id, record_id, 
                 refills_remaining FROM medrecappPrescription 
                 WHERE testid = ?1</sql>
        </sql-query>
    </weblogic-query>
...
</weblogic-rdbms-bean>

sql-query

Range of values:

Default value: n/a

Requirements: To use database-specific SQL, you must specify the database against which to execute the SQL in database-type.

Parent elements:

weblogic-rdbms-bean
  weblogic-query

Function

The sql-query element allows you to specify standard and database-specific SQL queries. EJB-QL queries that do not take advantage of WebLogic extensions to EJB-QL should be specified in the ejb-jar.xml deployment descriptor.

Prior to WebLogic Server 9.0, only EJB-QL queries (with or without WebLogic extensions) were supported; in this release of WebLogic Server, SQL queries, EJB-QL queries (with or without WebLogic extensions), or a combination of the two are supported.

Example

<sql-query>
    <sql-shape-name>...</sql-shape-name>
    <sql>...</sql>
    <database-specific-sql>...</database-specific-sql>
    <database-type>...</database-type>
    <sql>...</sql>
    <unknown-primary-key-field>...</unknown-primary-key-field>
    <cmp-field>...</cmp-field>
</sql-query>

sql-select-distinct

Range of values: True | False

Default value: False

Parent elements:

weblogic-query

Note:

This element is deprecated. To achieve the same functionality, use the SELECT DISTINCT clause directly in finder queries.

Function

The sql-select-distinct element controls whether the generated SQL SELECT statement will contain a a DISTINCT qualifier. Using the DISTINCT qualifier causes the database to return unique rows.

Oracle database does not allow use of a SELECT DISTINCT with a FOR UPDATE clause. Therefore, you cannot use the sql-select-distinct element if any bean in the calling chain has a method with isolation-level of TransactionReadCommittedForUpdate. You specify the transaction-isolation element in the weblogic-ejb-jar.xml.

Example

The XML example contains the element shown here:

<sql-select-distinct>True</sql-select-distinct>

sql-shape

Range of values:

Default value:

Parent elements:

weblogic-rdbms-jar
  weblogic-rdbms-bean
    sql-query

Function

The sql-shape element describes the data that is returned by a SQL query. Specifying sql-shape is necessary because databases do not always provide this information. Usually the sql-shape element should simply specify the database tables and columns that are being returned. For more complex queries, sql-shape should also specify the relationships that are present in the data that is returned by the database, and whether there are aggregate columns that should be passed through (should not be mapped to anything).

Example

sql-shape
    description
    sql-shape-name
    table
    pass-through-columns
    ejb-relation-name

sql-shape-name

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-rdbms-jar
  weblogic-rdbms-bean
    weblogic-query
      sql-query
        sql-shape

Function

The sql-shape-name element can be used to associate a sql-shape with multiple queries. If you have multiple queries that use the same sql-shape, you can define the shape once and use it multiple times by referencing sql-shape-name.

Example

See sql-shape.

table-map

Range of values: n/a

Default value: n/a

Requirements: Each table-map element must contain a mapping for the bean's primary key fields.

Parent elements:

weblogic-rdbms-bean

Function

A CMP bean can be mapped to one or more DBMS tables. The table-map element specifies a mapping between the cmp-fields of a bean and the columns of a table for all of the cmp-fields mapped to that table. If you map a CMP bean to multiple DBMS tables, then you must specify a table-map element for each of the tables.

When you map a CMP bean to multiple tables, each table contains a row that maps to a particular bean instance. Consequently, all tables will contain the same number of rows at any point in time. In addition, each table contains the same set of homogeneous primary key values. Therefore, each table must have the same number of primary key columns and corresponding primary key columns in different tables must have the same type, although they may have different names.

Each table-map element must specify a mapping from the primary key column(s) for a particular table to the primary key field(s) of the bean. You can only map non-primary key fields to a single table.

For information about using the verify-rows, verify-columns, and optimistic-column elements, see Check Data for Validity with Optimistic Concurrency.

Example

The table-map element can contain the elements shown here:

<table-map>
    <table-name>DeptTable</table-name>
    <field-map>
        <cmp-field>deptId1</cmp-field>
        <dbms-column>t1_deptId1_column</dbms-column>
    </field-map>
    <field-map>
        <cmp-field>deptId2</cmp-field>
        <dbms-column>t1_deptId2_column</dbms-column>
    </field-map>
    <field-map>
        <cmp-field>location</cmp-field>
        <dbms-column>location_column</dbms-column>
    </field-map>
        <cmp-field>budget</cmp-field>
        <dbms-column>budget</dbms-column>
    </field-map>
    <verify-rows>Read</verify-rows>
    <verify-columns>Version</verify-columns>
    <optimistic-column>ROW_VERSION</optimistic-column>        
    <trigger-updates-optimistic-column>False
    </trigger-updates-optimistic-column>
    <version-column-initial-value>0</version-column-initial-value>
</table-map>

table-name

Range of values: Valid, fully qualified SQL name of the source table in the database.

Default value:

Requirements: table-name must be set in all cases.

Parent elements:

weblogic-rdbms-bean
  weblogic-rdbms-relation

Function

The fully-qualified SQL name of the table. The user defined for the data-source for this bean must have read and write privileges for this table, but does not necessarily need schema modification privileges.

Example

<weblogic-rdbms-jar>
    <weblogic-rdbms-bean>
        <ejb-name>containerManaged</ejb-name>
        <data-source-jndi-name>examples-dataSource-demoPool</data-source-jndi-name>
        <table-name>ejbAccounts</table-name>
    </weblogic-rdbms-bean>
</weblogic-rdbms-jar>

trigger-updates-optimistic-column

Range of values: True | False

Default value: False

Parent elements:

weblogic-rdbms-bean
  table-map

Function

The trigger-updates-optimistic-column element, introduced in WebLogic Server 9.0, indicates whether you want the EJB container to automatically update the database column value specified in optimistic-column that is used for concurrency checking. By default, the value of trigger-updates-optimistic-column is False, and the EJB container automatically updates the database column specified in optimistic-column whenever it sends SQL UPDATE statements to JDBC. If you have legacy applications that use database triggers to update the version values whenever the legacy application updates a database row and you do not want the EJB container to automatically update version values, set the value of this element to True.


Note:

If you set trigger-updates-optimistic-column to True, you must also ensure that your database triggers initialize the version column in the database when the bean is created.

Example

See table-map.

unknown-primary-key-field

Range of values: A valid datatype

Default value: n/a

Parent elements:

weblogic-rdbms-bean

Function

The unknown-primary-key-field element allows you to specify which of your cmp fields should be used as the primary key when the primary key is not specified in the ejb-jar.xml descriptor. The specified primary key field must be mapped to a database column using the field-map element. If the specified primary key field was not declared as a cmp field in the ejb-jar.xml descriptor, automatic key generation must be enabled and the primary key type will be java.lang.Long.

Example

See weblogic-rdbms-bean.

use-select-for-update

Range of values: True | False

Default value: False

Parent elements:

weblogic-rdbms-bean

Function

Enforces pessimistic concurrency on a per-bean basis. Specifying True causes SELECT ... FOR UPDATE to be used whenever the bean is loaded from the database. This is different from the transaction isolation level of TransactionReadCommittedForUpdate in that this is set at the bean level rather than the transaction level.


Note:

When using a pessimistic locking strategy (for example, HOLDLOCK) with Sybase JConnect drivers, you must specify SELECT_OPENS_CURSOR=true to generate a cursor when the query contains a FOR UPDATE clause.

Example

<weblogic-rdbms.jar>
    <weblogic-rdbms-bean>
        <ejb-name>containerManaged</ejb-name>
        <use-select-for-update>True</use-select-for-update>
    /weblogic-rdbms-bean>
</weblogic-rdbms-jar>

validate-db-schema-with

Range of values: MetaData | TableQuery

Default value: TableQuery

Parent elements:

weblogic-rdbms-jar

Function

The validate-db-schema-with element specifies that container-managed persistence checks that beans have been mapped to a valid database schema during deployment.

If you specify MetaData WebLogic Server uses the JDBC metadata to validate the schema.

If you specify TableQuery, the default setting, WebLogic Server queries the tables directly to verify that they have the schema expected by CMP runtime.

Example

An example of the validate-db-schema-with element is shown here:

<validate-db-schema-with>TableQuery</validate-db-schema-with>

verify-columns

Range of values: Read | Modified | Version | Timestamp

Default value: none

Requirements: table-name must be set in all cases.

Parent elements:

weblogic-rdbms-bean
  table-map

Function

The verify-columns element specifies the columns in a table that you want WebLogic Server to check for validity when you use the optimistic concurrency strategy. WebLogic Server checks columns at the end of a transaction, before committing it to the database, to make sure that no other transaction has modified the data.

See Choosing a Concurrency Strategy for more information.

Example

<verify-columns>Modified</verify-columns>

verify-rows

Range of values: Read | Modified

Default value: Modified

Requirements: table-name must be set in all cases.

Parent elements:

weblogic-rdbms-bean
  table-map

Function

The verify-rows element specifies the rows in a table that the EJB container should check when optimistic concurrency is used.

  • Modified— only rows that are updated or deleted by a transaction are checked. This value ensures that two transactions do not update the same row concurrently, resulting in a lost update, but allows reads and updates of different transactions to be interleaved. This results in a level of consistency that falls between the ANSI READ_COMMITTED and REPEATABLE_READ levels of consistency.

  • Read—specifies that any row that is read by the transaction should be checked. This includes both rows that are simply read and rows that are read and then updated or deleted by the transaction. Specifying a value of Read results in additional overhead since it generally increases the amount of optimistic checking the EJB container must perform. With the Read option, committed transactions read a set of rows that are guaranteed not to be modified by another transaction until after the transaction commits.This results in a high level of consistency which is very close to the ANSI definition of SERIALIZABLE consistency.


    Note:

    If verify-rows is set to Read then the verify-columns element cannot have a value of Modified, as this combination would result in the EJB container checking only the modified rows.

See Choosing a Concurrency Strategy for more information.

Example

<verify-rows>Modified</verify-rows>

version-column-initial-value

Range of values: 0 or any positive integer

Default value: n/a

Parent elements:

weblogic-rdbms-bean
  table-map

Function

The version-column-initial-value element, introduced in WebLogic Server 9.0, specifies the initial value of the version column used to implement optimistic concurrency. The version column is the database column you specify in the optimistic-column element. For more information, see optimistic-column.

Example

See table-map.

weblogic-ql

Range of values:

Default value:

Parent elements:

weblogic-rdbms-bean
  weblogic-query

Function

The weblogic-ql element specifies a query that contains a WebLogic specific extension to the ejb-ql language. You should specify queries that only use standard EJB-QL language features in the ejb-jar.xml deployment descriptor.

Example

See weblogic-query.

weblogic-query

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-rdbms-bean

Function

The weblogic-query element allows you to specify queries that use standard or database-specific SQL or WebLogic-specific extensions to EJB-QL. Queries that do not take advantage of SQL or WebLogic extensions to EJB-QL should be specified in the ejb-jar.xml deployment descriptor.

The weblogic-query element is also used to associate a field-group with the query if the query retrieves an entity bean that should be pre-loaded into the cache by the query.

Example

The weblogic-query element can contain the elements shown here:

<weblogic-query>
    <description>...</description>
    <query-method>
        <method-name>findBigAccounts</method-name>
        <method-params>
            <method-param>double</method-param>
        </method-params>
    </query-method>
    <ejb-ql-query>
        <weblogic-ql>WHERE BALANCE>10000 ORDER BY NAME
        </weblogic-ql>
        <group-name>...</group-name>
        <caching-name>...</caching-name>
    </ejb-ql-query>
    <sql-query>
        <sql-shape>...</sql-shape>
        <sql>SELECT date_prescribed, dosage, drug, id, frequency, instructions,
             pat_id, issuing_phys_id, record_id, refills_remaining FROM
             medrecappPrescription WHERE testid = ?1</sql>
        <database-specific-sql>
            <database-type>SQLServer</database-type>
            <sql>SELECT name, phone, location, testid FROM medrecappPharmacyBeanTable
                 WHERE testid = ?1 AND
                 SUBSTRING(testid, 1,5) = 'local' ORDER BY name</sql>
        </database-specific-sql>
    </sql-query>
    <max-elements>...</max-elements>
    <include-updates>...</include-updates>
    <sql-select-distinct>...</sql-select-distinct>
</weblogic-query>

weblogic-rdbms-bean

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-rdbms-jar

Function

The weblogic-rdbms-bean specifies an entity bean that is managed by the WebLogic RDBMS CMP persistence type.

Example

weblogic-rdbms-bean
    ejb-name
    data-source-jndi-name
    unkonown-primary-key-field
    table-map
    field-group
    relationship-caching
    weblogic-query
    dalay-database-insert-until
    automatic-key-generation
    check-exists-on-method

weblogic-rdbms-jar

This section describes and provides an example of the weblogic-rdbms-jar element.

Function

The weblogic-rdbms-jar element is the root level element of a WebLogic RDBMS CMP deployment descriptor. This element contains the deployment information for one or more entity beans and an optional set of relations.

Example

The XML structure of weblogic-rdbms-jar is:

weblogic-rdbms-jar
    weblogic-rdbms-bean
    weblogic-rdbms-relation
    create-default-dbms-tables
    validate-db-schema-with
    database-type

weblogic-rdbms-relation

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-rdbms-jar

Function

The weblogic-rdbms-relation element represents a single relationship that is managed by the WebLogic CMP persistence type. deployment descriptor. WebLogic Server supports the following three relationship mappings:

  • For one-to-one relationships, the mapping is from a foreign key in one bean to the primary key of the other bean.

  • For one-to-many relationships, the mapping is also from a foreign key in one bean to the primary key of another bean.

  • For many-to-many relationships, the mapping involves a join table. Each row in the join table contains two foreign keys that map to the primary keys of the entities involved in the relationship.

For more information on container managed relationships, see Using Container-Managed Relationships (CMRs).

Examples

See the following sections for examples of how one-to-one, one-to-many, and many-to-many relationships are configured.

Defining a One-to-One Relationship

Example C-6 shows the weblogic-rdbms-bean element that defines a one-to-one relationship between the entities defined in Example C-4 and Example C-5. The weblogic-rdbms-relation element is in the weblogic-cmp-jar.xml file, after the weblogic-rdbms-bean elements.

Example C-4 Bean 1

<weblogic-rdbms-bean>
    <ejb-name>CountryEJB</ejb-name>
    <data-source-jndi-name>wlsd21-datasource</data-source-jndi-name>
    <table-map>
        <table-name>EXAMPLE07_COUNTRY</table-name>
        <field-map>
            <cmp-field>name</cmp-field>
            <dbms-column>NAME</dbms-column>
        </field-map>
        <field-map>
            <cmp-field>continent</cmp-field>
            <dbms-column>CONTINENT</dbms-column>
        </field-map>
    </table-map>
</weblogic-rdbms-bean>

Example C-5 Bean 2

<weblogic-rdbms-bean>
    <ejb-name>CapitalEJB</ejb-name>
    <data-source-jndi-name>wlsd21-datasource</data-source-jndi-name>
    <table-map>
        <table-name>EXAMPLE07_CAPITAL</table-name>
        <field-map>
            <cmp-field>CAPITAL_NAME</cmp-field>
            <dbms-column>NAME</dbms-column>
        </field-map>
        <field-map>
            <cmp-field>continent</cmp-field>
            <dbms-column>CONTINENT</dbms-column>
        </field-map>
    </table-map>
</weblogic-rdbms-bean>

Example C-6 <weblogic-rdbms-relation> Element for a One-to-One Relationship

<weblogic-rdbms-relation>
    <relation-name>CountryCapitalRel</relation-name>
    <weblogic-relationship-role>
        <relationship-role-name>CountryRole</relationship-role-name>
        <relationship-role-map>
            <column-map>
                <foreign-key-column>CAPITAL_NAME</foreign-key-column>
                <key-column>NAME</key-column>
            </column-map>
        </relationship-role-map>
    </weblogic-relationship-role>
</weblogic-rdbms-relation>

Note:

NAME is the column name for the primary key located in the Capital table.

<relationship-role-name> contains the relation field specified in <cmr-field> in the <ejb-relationship-role> element in ejb-jar.xml.


Defining a One-to-Many Relationship

Example C-7 contains a sample <weblogic-rdbms-relation> element that defines a one-to-many relationship:

Example C-7 <weblogic-rdbms-relation> Element for a One-to-Many Relationship

<weblogic-rdbms-relation>
    <relation-name>OwnerDogRel</relation-name>
    <weblogic-relationship-role>
        <relationship-role-name>DogRole</relationship-role-name>
        <relationship-role-map>
            <column-map>
                <foreign-key-column>OWNER_NAME</foreign-<key-column>
                <key-column>NAME</key-column>
            &)lt;/column-map>
        <relationship-role-map> 
    </weblogic-relationship-role>
</weblogic-rdbms-relation>

Note:

<relationship-role-name> contains the relation field specified in <cmr-field> in the <ejb-relationship-role> element in ejb-jar.xml.

<foreign-key-column> must specify the column in the table on the "many" side of the relationship.


Defining a Many-to-Many Relationship

A WebLogic Server many-to-many relationship involves the physical mapping of a join table. Each row in the join table contains two foreign keys that maps to the primary keys of the entities involved in the relationship.

The following example shows a many-to-many relationship between the FRIENDS bean and the EMPLOYEES bean.

Example C-8 <weblogic-rdbms-relation> Element for a Many-to-Many Relationship

<weblogic-rdbms-relation>
    <relation-name>friends</relation-name>
    <table-name>FRIENDS</table-name>
    <weblogic-relationship-role>
        <relationship-role-name>friend</relationship-role-name>
        <relationship-role-map>
            <column-map>
                <foreign-key-column>first-friend-id</foreign-key-column>
                <key-column>id</key-column>
            </column-map
        </relationship-role-map>
    </weblogic-relationship-role>
    <weblogic-relationship-role>
        <relationship-role-name>second-friend</relationship-role-name>
        <relationship-role-map>
            <column-map>
                <foreign-key-column>second-friend-id</foreign-key-column>
                <key-column>id</key-column>
            </column-map>
        </relationship-role-map>
    </weblogic-relationship-role>
</weblogic-rdbms-relation>

In Figure C-0, the FRIENDS join table has two columns, called first-friend-id and second-friend-id. Each column contains a foreign key that designates a particular employee who is a friend of another employee. The primary key column (key-column) of the EMPLOYEES table is id. For this example, assume that the EMPLOYEES bean is mapped to a single table. If the EMPLOYEES bean is mapped to multiple tables, then the table containing the primary key column (key-column) must be specified in the relationship-role-map. For more information, see relationship-role-map.

weblogic-relationship-role

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-rdbms-jar
  weblogic-rdbms-relation

Function

The weblogic-relationship-role element specifies the following DBMS schema information for an ejb-relationship-role specified in ejb-jar.xml:

  • The relationship-role-map sub-element specifies the mapping between a foreign key and a primary key, for one side of a relationship. For a 1-1 or 1-n relationship, only the role on the foreign-key side of the relationship specifies a mapping. Both roles specify a mapping for a m-m relationship. For details and examples, see relationship-role-map.

  • A group-name can be used to indicate the field-group to be loaded when the bean corresponding to the role is loaded as a result of traversing the relationship, i.e. calling a cmr getXXX method.

  • The db-cascade-delete tag can to used to specify that cascade deletes use the built-in cascade delete facilities of the underlying DBMS. For more information, see db-cascade-delete.

For more information about container-managed relationships, see Using Container-Managed Relationships (CMRs).

Example

<weblogic-relationship-role>
    <relationship-role-name>...</relationship-role-name>
    <group-name> ....</group-name>
    <relationship-role-map>...
        ....
    </relationship-role-map> 
    <db-cascade-delete/>
</weblogic-relationship-role>
PKECB)PK;wEOEBPS/understanding.htm Understanding Enterprise JavaBeans

2 Understanding Enterprise JavaBeans

These sections briefly review the different Enterprise JavaBean (EJB) types and the functions they can serve in an application, and describe how they work with other application objects and WebLogic Server.

It is assumed the reader is familiar with Java programming and EJB 2.x concepts and features.

How Do Applications Use EJBs?

These sections describe the purpose and capabilities of each bean type:

Session EJBs Implement Business Logic

Session beans implement business logic. A session bean instance serves one client at a time. There are two types of session beans: stateful and stateless.

Stateless Session Beans

A stateless session bean does not store session or client state information between invocations—the only state it might contain is not specific to a client, for instance, a cached database connection or a reference to another EJB. At most, a stateless session bean may store state for the duration of a method invocation. When a method completes, state information is not retained. Any instance of a stateless session bean can serve any client—any instance is equivalent. Stateless session beans can provide better performance than stateful session beans, because each stateless session bean instance can support multiple clients, albeit one at a time.

Example: An Internet application that allows visitors to click a "Contact Us" link and send an email could use a stateless session bean to generate the email, based on the to and from information gathered from the user by a JSP.

Stateful Session Beans

Stateful session beans maintain state information that reflects the interaction between the bean and a particular client across methods and transactions. A stateful session bean can manage interactions between a client and other enterprise beans, or manage a workflow.

Example: A company Web site that allows employees to view and update personal profile information could use a stateful session bean to call a variety of other beans to provide the services required by a user, after the user clicks "View my Data" on a page:

  • Accept the login data from a JSP, and call another EJB whose job it is to validate the login data.

  • Send confirmation of authorization to the JSP.

  • Call a bean that accesses profile information for the authorized user.

Entity EJBs Maintain Persistent Data

An entity bean represents a set of persistent data, usually rows in a database, and provides methods for maintaining or reading that data. An entity bean is uniquely identified by a primary key, and can provide services to multiple clients simultaneously. Entity beans can participate in relationships with other entity beans. The relationships between entity beans are a function of the real-world entities that the entity beans model. An entity bean's fields and its relationships to other entity beans are defined in an object schema, which is specified in the bean's ejb-jar.xml deployment descriptor.

An entity bean can have other bean types, such as message-driven or session beans, as clients, or be directly accessed by Web components. The client uses the entity bean to access data in a persistent store. An entity bean encapsulates the mechanics of database access, isolating that complexity from its clients and de-coupling physical database details from business logic.

Example: The stateful session bean in the previous example, which orchestrates services for an employee accessing personal profile information on a company intranet, could use an entity bean for getting and updating the employee's profile.

Message-Driven Beans Implement Loosely Coupled Business Logic

A message-driven bean implements loosely coupled or asynchronous business logic in which the response to a request need not be immediate. A message-driven bean receives messages from a JMS Queue or Topic, and performs business logic based on the message contents. It is an asynchronous interface between EJBs and JMS.

Throughout its life cycle, an MDB instance can process messages from multiple clients, although not simultaneously. It does not retain state for a specific client. All instances of a message-driven bean are equivalent—the EJB container can assign a message to any MDB instance. The container can pool these instances to allow streams of messages to be processed concurrently.

The EJB container interacts directly with a message-driven bean—creating bean instances and passing JMS messages to those instances as necessary. The container creates bean instances at deployment time, adding and removing instances during operation based on message traffic.

For detailed information, see Programming Message-Driven Beans for Oracle WebLogic Server.

Example: In an on-line shopping application, where the process of taking an order from a customer results in a process that issues a purchase order to a supplier, the supplier ordering process could be implemented by a message-driven bean. While taking the customer order always results in placing a supplier order, the steps are loosely coupled because it is not necessary to generate the supplier order before confirming the customer order. It is acceptable or beneficial for customer orders to "stack up" before the associated supplier orders are issued.

EJB Anatomy and Environment

These sections briefly describe classes required for each bean type, the EJB run-time environment, and the deployment descriptor files that govern a bean's run-time behavior.

EJB Components

The composition of a bean varies by bean type. Table 2-1 defines the classes that make up each type of EJB, and defines the purpose of the class type.

Table 2-1 Components of an EJB

EJB ComponentDescriptionStateless SessionStateful SessionEntityMDB

Remote interface

The remote interface exposes business logic to remote clients—clients running in a separate application from the EJB. It defines the business methods a remote client can call.

Yes

Yes

Yes

No

Local interface

The local interface exposes business logic to local clients—those running in the same application as the EJB. It defines the business methods a local client can call.

Note: Not available for 1.1 EJBs.

Yes

Yes

Yes

No

Local home interface

The local home interface, also referred to as an EJB factory or life-cycle interface, provides methods that local clients—those running in the same application as the EJB—can use to create, remove, and in the case of an entity bean, find instances of the bean.

The local home interface also has "home methods"—business logic that is not specific to a particular bean instance.

Yes

Yes

Yes

No

Remote home interface

The remote home interface, also referred to as an EJB factory, or life-cycle interface, provides methods that remote clients—those running in a separate application from the EJB—can use to create, remove, and find instances of the bean.

Yes

Yes

Yes

No

Bean class

The bean class implements business logic.

Yes

Yes

Yes

Yes

Primary key class

Only entity beans have a primary key class. The primary key class maps to one or more fields in a database—identifying the persistent data to which the entity bean corresponds.

No

No

Yes

No


The EJB Container

An EJB container is a run-time container for beans that are deployed to an application server. The container is automatically created when the application server starts up, and serves as an interface between a bean and run-time services such as:

  • Life cycle management

  • Code generation

  • Persistence management

  • Security

  • Transaction management

  • Locking and concurrency control

EJB Deployment Descriptors

The structure of a bean and its run-time behavior are defined in one or more XML deployment descriptor files. Programmers create deployment descriptors during the EJB packaging process, and the descriptors become a part of the EJB deployment when the bean is compiled.

WebLogic Server EJBs have three deployment descriptors:

  • ejb-jar.xml—The standard Java EE deployment descriptor. All beans must be specified in an ejb-jar.xml. An ejb-jar.xml can specify multiple beans that will be deployed together.

  • weblogic-ejb-jar.xml—WebLogic Server-specific deployment descriptor that contains elements related to WebLogic Server features such as clustering, caching, and transactions. This file is required if your beans take advantage of WebLogic Server-specific features. Like ejb-jar.xml, weblogic-ejb-jar.xml can specify multiple beans that will be deployed together. See "weblogic-ejb-jar.xml Deployment Descriptor Reference" in Programming WebLogic Enterprise JavaBeans for Oracle WebLogic Server.

  • weblogic-cmp-jar.xml—WebLogic Server-specific deployment descriptor that contains elements related to container-managed persistence for entity beans. Entity beans that use container-managed persistence must be specified in a weblogic-cmp-jar.xml file. See "weblogic-cmp-jar.xml Deployment Descriptor Reference" in Programming WebLogic Enterprise JavaBeans for Oracle WebLogic Server.

Key Deployment Element Mappings

As described in EJB Deployment Descriptors, a WebLogic Server EJB's runtime behavior can be controlled by elements in three different descriptor files: ejb-jar.xml, weblogic-ejb-jar.xml, and weblogic-cmp-jar.xml.

Table 2-2 lists the elements whose values should match in each descriptor file. The elements listed in the table are defined in Bean and Resource References and Security Roles.

Table 2-2 Element Mapping Among Descriptor Files

Map this element...in this element of ejb-jar.xml...to the same element in this element of weblogic-ejb-jar.xml...and to this element in weblogic-cmp-jar.xml...

role-name

security-role

security-role-assignment

N/A

ejb-name

message-driven, entity, or session

weblogic-enterprise-bean

weblogic-rdbms-bean

ejb-ref-name

assembly-descriptor

ejb-reference-description if the referenced bean runs in a different container than the current bean.

N/A

res-ref-name

resource-ref

resource-description

N/A


Bean and Resource References

Each descriptor file contains elements that identify a bean, and the runtime factory resources it uses:

  • ejb-name—the name used to identify a bean in each deployment descriptor file, independent of the name that application code uses to refer to the bean.

  • ejb-ref-name—the name by which a bean in another JAR is referred to in the referencing bean's code.

  • res-ref-name—the name by which a resource factory is referred to in the referencing bean's code.

A given bean or resource factory is identified by the same value in each descriptor file that contains it. Table 2-1 lists the bean and resource references elements, and their location in each descriptor file.

For instance, for a container-managed persistence entity bean named LineItem, this line:

<ejb-name>LineItem</ejb-name> 

would appear in the:

  • assembly-descriptor element of ejb-jar.xml

  • enterprise-bean element of weblogic-ejb-jar.xml

  • weblogic-rdbms-bean element of weblogic-cmp-jar.xml

Security Roles

Security roles are defined in the role-name element in ejb-jar.xml and weblogic-ejb-jar.xml.

For information on:

EJBs, Clients, and Application Objects

Figure 2-1 illustrates how EJBs typically relate to other components of a WebLogic Server application and to clients.

Figure 2-1 EJBs and Other Application Components

Description of Figure 2-1 follows

An EJB can be accessed by server-side or client-side objects such as servlets, Java client applications, other EJBs, applets, and non-Java clients.

Any client of an EJB, whether in the same or a different application, accesses it in a similar fashion. WebLogic Server automatically creates implementations of an EJB's home and business interfaces that can function remotely, unless the bean has only a local interface.

All EJBs must specify their environment properties using the Java Naming and Directory Interface (JNDI). You can configure the JNDI namespaces of EJB clients to include the home interfaces for EJBs that reside anywhere on the network—on multiple machines, application servers, or containers.

Most beans do not require a global JNDI name—specified in the jndi-name and local-jndi-name elements of weblogic-ejb-jar.xml. Most beans reference to each other using ejb-links, as described in Using EJB Links.

Because of network overhead, it is more efficient to access beans from a client on the same machine than from a remote client, and even more efficient if the client is in the same application.

See Programming Client Access to EJBs for information on programming client access to an EJB.

EJB Communications

WebLogic Server EJBs use:

  • T3—To communicate with remote objects. T3 is a WebLogic-proprietary remote network protocol that implements the Remote Method Invocation (RMI) protocol.

  • RMI—To communicate with remote objects. RMI enables an application to obtain a reference to an object located elsewhere in the network, and to invoke methods on that object as though it were co-located with the client on the same JVM locally in the client's virtual machine.

    An EJB with a remote interface is an RMI object. An EJB's remote interface extends java.rmi.remote. For more information on WebLogic RMI, see Programming RMI for Oracle WebLogic Server.

  • HTTP—An EJB can obtain an HTTP connection to a Web server external to the WebLogic Server environment by using the java.net.URL resource connection factory. For more information, see Configuring EJBs to Send Requests to a URL.

You can specify the attributes of the network connection an EJB uses by binding the EJB to a WebLogic Server custom network channel. For more information, see Configuring Network Communications for an EJB.

EJBs and Message Destination References

In this release of WebLogic Server, you can use logical message destinations to map a logical message destination, defined in ejb-jar.xml, to an actual message destination, defined in weblogic-ejb-jar.xml, as described in "Configuring EJBs to Use Logical Message Destinations" in Oracle Fusion Middleware Programming Message-Driven Beans for Oracle WebLogic Server.

If a message destination reference cannot be resolved during deployment, a warning is issued but the deployment will succeed. MDBs linked to unavailable message destinations periodically attempt to connect to the message destination. Until the message destination is available, attempts to look up message-destination-references declared in ejb-jar.xml fail with a javax.naming.NamingException. When the message destination becomes available, the MDBs will connect to it and service messages from it.

WebLogic Server Value-Added EJB Features

This section describes key WebLogic Server features that ease the process of EJB development, and enhance the performance, reliability, and availability of EJB applications.

Performance-Enhancing Features for WebLogic Server EJBs

WebLogic Server supports pooling, caching, and other features that improve the response time and performance of EJBs. In a production environment, these features can reduce the time it takes for a client to obtain an EJB instance and access and maintain persistent data.

Pooling Improves EJB Response Time

WebLogic Server maintains a free pool of ready-to-use EJB instances for stateless session beans, message-driven beans, and entity beans. The EJB container creates a configurable number of bean instances at startup, so that a new instance does not have to be created for every request. When a client is done with an EJB instance, the container returns it to the pool for reuse. For more information see:

In this release of WebLogic Server, Administrators can initialize EJB pools on demand via the Administration Console. When an EJB's pool is initialized, it is reset to the state it was immediately after the EJB was deployed. For more information, see "Initialize the idle bean cache and pool of an EJB" in Oracle WebLogic Server Administration Console Help.

Caching Improves EJB Performance

WebLogic Server supports caching for stateful session beans and entity beans.

An inactive cached bean instance can be passivated—removed from the cache and written to disk—and restored to memory later as necessary. Passivating bean instances optimizes use of system resources.

You can configure the size of the cache, and related behaviors such as rules for removing beans from the cache. Caching is supported for entity EJBs, whether they use container-managed or bean-managed persistence.

Additionally, in this release of WebLogic Server, Administrators can initialize EJB caches on demand via the Administration Console. When an EJB's cache is initialized, it is reset to the state it was in immediately after the EJB was deployed. For more information, see "Initialize the idle bean cache and pool of an EJB" in Oracle WebLogic Server Administration Console Help.

For more information, see:

Additional caching features are available for EJBs that use container-managed persistence, as described in the following section.

Additional Caching Capabilities for CMP Entities

WebLogic Server provides these caching capabilities for entity beans that use container managed persistence:

  • Relationship caching—Relationship caching improves the performance of entity beans by loadintAg related beans into the cache and avoiding multiple queries by issuing a join query for the related beans. For more information, see Relationship Caching.

  • Application-level caching—Application-level caching, also known as "combined caching," allows multiple entity beans that are part of the same Java EE application to share a single runtime cache. For more information, see Configuring Application-Level Caching.

  • Caching between transactions—Use caching between transactions or long term caching to enable the EJB container to cache an entity bean's persistent data between transactions. For more information, see Limiting Database Reads with cache-between-transactions.

Field Groups for Efficient Queries (CMP Entities)

A group specifies a set of persistent attributes of an entity bean. A field-group represents a subset of the container-managed persistence (CMP) and container-managed relation (CMR) fields of a bean. You can put related fields in a bean into groups that are faulted into memory together as a unit. You can associate a group with a query or relationship, so that when a bean is loaded as the result of executing a query or following a relationship, only the fields mentioned in the group are loaded. For more information, see Specifying Field Groups.

Configurable Write Behaviors

You can configure the behavior of the ejbLoad() and ejbStore() methods to enhance performance, by avoiding unnecessary calls to ejbStore(). As appropriate, you can ensure that WebLogic Server calls ejbStore() after each method call, rather than at the conclusion of the transaction. For more information, see Understanding ejbLoad() and ejbStore() Behavior.

Operation Ordering and Batching (CMP Entities)

WebLogic Server allows you to batch and order multiple database operations so that they can be completed in a single database "round-trip". This allows you to avoid the bottlenecks that might otherwise occur when multiple entity instances are affected by a single transaction. For more information, see Ordering and Batching Operations.

Optimized Database Updates (CMP Entities)

In this release of WebLogic Server, for CMP 2.0 entity beans, the setXXX() method does not write the values of unchanged primitive and immutable fields to the database. This optimization improves performance, especially in applications with a high volume of database updates.

Read-Only Pattern and Read-Only Invalidation (CMP Entities)

For EJB data that is only occasionally updated, you can create a "read-mostly pattern" by implementing a combination of read-only and read-write EJBs. If you use the read-mostly pattern, you can use multicast invalidation to maintain data consistency—an efficient mechanism for invalidating read-only cached data after updates. Use of the invalidate() method after the transaction update has completed invalidates the local cache and results in a multicast message sent to the other servers in the cluster to invalidate their cached copies. For more information, see Using the Read-Mostly Pattern.

CMP Beans Increase Developer Productivity

WebLogic Server provides a variety of value-added database access features for entity beans that use container-managed persistence:

Automatic Primary Key Generation (CMP Entities)

WebLogic Server supports multiple methods to automatically generate simple primary key for CMP entity EJBs, including use of an Oracle SEQUENCE (which can be automatically generated by WebLogic Server). For more information, see Automatically Generating Primary Keys.

Automatic Table Creation (CMP Entities)

You can configure the EJB container to automatically change the underlying table schema as entity beans change, ensuring that tables always reflect the most recent object-relationship mapping. For more information, see Automatic Table Creation (Development Only).

Dynamic Queries (CMP Entities)

WebLogic Server allows you to construct and execute EJB-QL queries programmatically in your application code. This allows you to create and execute new queries without having to update and deploy an EJB. It also reduces the size and complexity of the EJB deployment descriptors. For more information, see Choosing a Concurrency Strategy.

Reliability and Availability Features

WebLogic Server EJBs can be deployed to a cluster, allowing support for load balancing, and failover for remote clients of an EJB. EJBs must be deployed to all clustered servers.

A WebLogic Server cluster consists of multiple WebLogic Server server instances running simultaneously and working together to provide increased scalability and reliability. A cluster appears to clients as a single WebLogic Server instance. The server instances that constitute a cluster can run on the same machine, or be located on different machines.

Failover and load balancing for EJBs are handled by replica-aware stubs, which can locate instances of the object throughout the cluster. Replica-aware stubs are created for EJBs as a result of the object compilation process. EJBs can have two different replica-aware stubs: one for the EJBHome interface and one for the EJBObject interface. This allows some bean types to take advantage of load balancing and failover features at the home level when a client looks up an EJB object using the EJBHome stub and at the method level when a client makes method calls against the EJB using the EJBObject stub. Table 2-1 summarizes the load balancing and failover support (method level and home level) for each EJB type.

Load Balancing Among Clustered EJBs Increases Scalability

The bean stub contains the load balancing algorithm (or the call routing class) used to load balance method calls to the object. On each call, the stub can employ its load algorithm to choose which replica to call.

WebLogic Server clusters support multiple algorithms for load balancing clustered EJBs; the default is the round-robin method. For more information, see "Load Balancing in a Cluster" in Using Clusters for Oracle WebLogic Server.

All bean types support load balancing at the home level. All bean types, except read-write entity beans, support load balancing at the method level.


Note:

WebLogic Server does not always load-balance an object's method calls. In most cases, it is more efficient to use a replica that is collocated with the stub itself, rather than using a replica that resides on a remote server.

Failover for Clustered EJBs Increases Reliability

Failover for EJBs is accomplished using the EJBHome stub or, when supported, the EJBObject stub. When a client makes a call through a stub to a service that fails, the stub detects the failure and retries the call on another replica.

EJB failover requires that bean methods must be idempotent, and configured as such in weblogic-ejb-jar.xml. For more information see "Replication and Failover for EJBs and RMI Objects" in Using Clusters for Oracle WebLogic Server.

Table 2-3 summarizes failover and load balancing features for clustered EJBs.

Table 2-3 Failover and Load Balancing for Clustered EJBs

EJB TypeHome Level FailoverMethod Level FailoverNotes

Stateless Session

Supported

Supported

Stateless session EJB clustering behaviors are configured in weblogic-ejb-jar.xml. See WebLogic-Specific Configurable Behaviors for Session Beans.

Stateful session

Supported

Supported

The EJBObject stub maintains the location of the EJB's primary and secondary states. Secondary server instances are selected using the same rules defined in "Using Replication Groups" in Using Clusters for Oracle WebLogic Server.

Stateful session EJB clustering behaviors are configured in weblogic-ejb-jar.xml. See WebLogic-Specific Configurable Behaviors for Session Beans.

Read-Write Entity

Supported

Not supported

EJBHome stubs do not fail over in the event of a recoverable call failure.

Failover is not supported during method execution, only after method completion, or if the method fails to connect to a server instance.

A read-write bean's home obtains a local instance of the bean and returns a stub pinned to the local server instance.

Entity clustering behaviors are configured in weblogic-ejb-jar.xml. See Clustering Elements.

Read-Only Entity

Supported

Supported

EJBHome stubs do not failover in the event of a recoverable call failure.

Entity clustering behaviors are configured in weblogic-ejb-jar.xml. See Clustering Elements.

Message- Driven

N/A

N/A

WebLogic Java Messaging Service (JMS) supports clustering of JMS servers. For more information, see "JMS and Clustering" in Using Clusters for Oracle WebLogic Server.


For more information, see "Replication and Failover for EJBs and RMIs" and "Load Balancing for EJBs and RMI Objects" in Using Clusters for Oracle WebLogic Server.

Securing EJBs

Using WebLogic Server security features, you control both access to your EJBs (authorization) and verification of an EJB's identity when it interacts with other application components and other EJBs (authentication).

WebLogic Server enables application developers to build security into their EJB applications using Java EE and WebLogic Server deployment descriptors, or allows system administrators to control security on EJB applications from the WebLogic Server Administration Console. The latter option frees developers from having to code security, and provides administrators with a centralized tool for defining security policies on: entire enterprise applications (EARs); an EJB JAR containing multiple EJBs; a particular EJB within that JAR; or a single method within that EJB.

For more information about security and EJBs:

PKTT~tPK;wEOEBPS/design_best_practices.htm Designing Enterprise JavaBeans

3 Designing Enterprise JavaBeans

These sections discuss design options for WebLogic Server Enterprise JavaBeans (EJBs), bean behaviors to consider during the design process, and recommended design patterns.

It is assumed the reader is familiar with Java programming, EJB 2.x, and the features described in WebLogic Server Value-Added EJB Features.

After finalizing your bean design, refer to programming and other implementation topics in Chapter 4, "Implementing Enterprise JavaBeans."

Choosing the Right Bean Type

When you choose the bean type for a processing task, consider the different natures and capabilities of the various bean types.

Bean types vary in terms of the bean's relationship with its client. Some bean types stick with a client throughout a series of processes, serving as a sort of general contractor—acquiring and orchestrating services for the client. There are other bean types that act like subcontractors, they deliver the same single function to multiple client-oriented general contractor beans. A client-oriented bean keeps track of client interactions and other information associated with the client process, throughout a client session—a capability referred to as maintaining state. Beans that deliver commodity services to multiple client-oriented beans do not maintain state.

The following sections describe the client interaction and state management characteristics of each bean type.


Note:

For a basic overview of each bean type, including an example of a business process to which each bean type is well suited, see How Do Applications Use EJBs?.

Session Bean Features

A session bean represents a single client inside the server. To access an application that is deployed on the server, the client invokes the session bean's methods. The session bean performs work for its client, shielding the client from complexity by executing business tasks inside the server.

A session bean instance has a single client. Session beans are not persistent—when the client terminates, its session bean appears to terminate and is no longer associated with the client.

A session bean can be used as a facade, between Web applications and entity beans to contain complex interactions and reduce RMI calls. When a client application accesses a remote entity bean directly, each getter method is a remote call. A session facade bean can access the entity bean locally, collect the data in a structure, and return it by value. The two types of session beans, those that maintain state and those that do not, are described in the following sections.

Stateful Session Beans

Stateful session beans support conversational services with tightly-coupled clients. A stateful session bean accomplishes a task for a particular client. It maintains state for the duration of a client session. After session completion, state is not retained.

Stateful session beans are instantiated on a per client basis, and can multiply and consume resources rapidly.

Stateless Session Beans

Like a stateful session bean, a stateless session bean performs a task for a particular client. Unlike a stateful session bean, stateless session beans do not maintain client state. A stateless session bean may maintain state only for the duration of a method invocation. When the method is finished, the state is no longer retained.

Except during method invocation, all instances of a stateless bean are equivalent, allowing the EJB container to assign an instance to any client request. When a home interface creates a stateless bean, it returns a replica-aware stub that can route to any server where the bean is deployed. Because a stateless bean holds no state on behalf of the client, the stub is free to route any call to any server that hosts the bean.

Stateless Beans Offer Performance and Scalability Advantages

Because stateless session beans are never written to secondary storage, they typically offer better performance than stateful beans.

For applications that require large numbers of clients, stateless session beans offer better scalability than stateful session beans.

The system overhead of creating an instance is less for a stateless session bean than for a stateful session bean.

  • You can simply obtain a stateless session bean instance from the free pool.

  • A stateful session bean instance is instantiated upon client request, has to set the session context, and must be garbage-collected at the end of the session.

You can typically support more clients with a stateless session bean than a stateful session bean. A stateless session bean instance is only reserved for the duration of a single client request, while a stateful session bean is reserved for the duration of a session.

The number of stateless session bean instances required is usually roughly equivalent to the number of threads in the server execute queue—in the order of hundreds, while the number of stateful session bean instances required corresponds more closely to the number of clients of the application—which for some applications may be hundreds of thousands.

Exposing Stateless Session Beans as Web Services

In this release of WebLogic Server, you can expose stateless session beans as Web Services through the Web service endpoint interface. For more information, see Getting Started With JAX-WS Web Services for Oracle WebLogic Server.

Entity Bean Features

An entity bean represents a business object in a persistent storage mechanism. Some examples of business objects are customers, orders, and products. In the Java SE JDK, the persistent storage mechanism is a relational database. Typically, each entity bean has an underlying table in a relational database, and each instance of the bean corresponds to a row in that table.

Key Features of Entity Beans

These are the key features of entity beans:

  • Persistence—Entity bean persistence can be managed by the EJB container, or the bean itself. If a bean uses container-managed persistence, the EJB container automatically generates the necessary database access calls. The code that you write for the entity bean does not include these calls. With bean-managed persistence, you must write the database access code and include it in the bean.

  • Shared Access—Throughout its life cycle, an entity bean instance can support multiple clients, although not at the same time. Because the clients might want to change the same data, it is important that entity beans work within transactions. Typically, the EJB container provides transaction management. In this case, you specify the transaction attributes in the bean's ejb-jar.xml file that control how transactions are managed. You do not have to code the transaction boundaries in the bean—the container marks the boundaries for you. For information about transaction management, see Transaction Design and Management Options.

  • Primary Key—Each entity bean has a unique object identifier. A customer entity bean, for example, might be identified by a customer number. The unique identifier, or primary key, enables the client to locate a particular entity bean. For more information, see Using Container-Managed Relationships (CMRs).

  • Relationships—Like a table in a relational database, an entity bean may be related to other entity beans. You implement relationships differently for entity beans with bean-managed persistence and for those with container-managed persistence. With bean-managed persistence, the code that you write implements the relationships. But with container-managed persistence, the EJB container takes care of the relationships for you. For this reason, relationships in entity beans with container-managed persistence are often referred to as container-managed relationships. For more information, see Using Cascade Delete for Entities in CMRs.

Read-Write versus Read-Only Entity Beans

WebLogic Server supports two types of entity beans: read-write and read-only.

Read-only beans perform better than read-write beans, because they reduce the number of times that data is read from the database.

Some applications require the use of read-write entity beans—the choice depends on frequency of updates and data consistency requirements. Table 3-1 provide key guidelines.

Table 3-1 Comparing Read-Write and Read-Only Entity Beans

Application RequirementChoose read-write entity beans if...Choose read-only entity beans if...

Frequency of updates

Your application data is updated often.

Example: A real-time stock quote feed.

Your application data is not updated often, or at all.

Example: A swimwear catalogue.

Data consistency

Your application requires transactionally consistent snapshots of data as it is updated.

Example: An application that updates bank account balances.

You can tolerate some level of staleness in the data: it does not have to be completely up-to-date.

Example: A news feed. Users want to see the story as soon as it is in the database, but it is not updated transactionally.


Entity Bean Performance and Data Consistency Characteristics

These sections describe approaches for choosing the entity bean implementation, based on your requirements for performance and data consistency.

Use Read-Only Beans to Improve Performance If Stale Data Is Tolerable

Read-only entity beans are recommended whenever stale data is tolerable—they are suitable for product catalogs and the majority of content within many applications. Primary key-based reads are performed against a local entity cache that is invalided on a timer basis. Other queries are made against the database. Read-only entity beans perform three to four times faster than transactional entities.


Note:

A client can successfully call setter methods on a read-only entity bean; however, the data will never be moved into the persistent store.

Use Read-Write Beans for Higher Data Consistency

Read-write entity beans are recommended for applications that require high data consistency, for example, customer account maintenance. All reads and writes are performed against the database.


Note:

For entity beans that use bean-managed persistence, or EJB 1.1 entity beans that use container-managed persistence, you can reduce the number of database writes by specifying the isModified method in weblogic-ejb-jar.xml.

Combine Read-Only and Read-Write Beans to Optimize Performance

For read-mostly applications, characterized by frequent reads, and occasional updates (for instance, a catalog)—a combination of read-only and read-write beans that extend the read-only beans is suitable. The read-only bean provides fast, weakly consistent reads, while the read-write bean provides strongly consistent writes.

Use Session Facades to Optimize Performance for Remote Entity Beans

To avoid the overhead imposed by remote calls, avoid accessing remote EJB entity beans from client or servlet code. Instead, use a session bean, referred to as a facade, to contain complex interactions and reduce calls from Web applications to RMI objects. When a client application accesses a remote entity bean directly, each getter method is a remote call. A session facade bean can access the entity bean locally, collect the data in a structure, and return it by value.

Alternatively, there are no disadvantages to accessing a local entity bean instance directly from the Web tier—it is preferable to do so than to use a facade.

Avoid the Use of Transfer Objects

Avoid the use of transfer objects, also referred to as value objects or helper classes. (A transfer object is a serializable class within an EJB that groups related attributes, forming a composite value, which is used as the return type of a remote business method.)

To optimize performance, accessing local entity instances is always preferable to the use of transfer objects.

Message-Driven Beans

A message-driven bean (MDB) is an enterprise bean that allows Java EE applications to process messages asynchronously. An MDB acts as a JMS or JCA message listener, which is similar to an event listener except that it receives messages instead of events. The messages may be sent by any Java EE component—an application client, another enterprise bean, or a Web component—or by non-Java EE applications.

See Programming Message-Driven Beans for Oracle WebLogic Server.

Persistence Management Alternatives

Persistence management strategy determines how an entity bean's database access is performed.

Configure the persistence management strategy—either container-managed or bean-managed—for an entity bean in the persistence-type element in ejb-jar.xml.


Note:

You can specify the use of a third-party persistence service for entity beans that use container-managed persistence in the persistence-use element in weblogic-ejb-jar.xml.

Use Container-Managed Persistence (CMP) for Productivity and Portability

A CMP bean relies upon the EJB container for all database interaction. The bean does not contain code that accesses the database. Instead, the EJB container generates the database access methods, based on information about the entity bean's persistent fields and relationships, in weblogic-cmp-jar.xml. For more information, see "weblogic-cmp-jar.xml Deployment Descriptor Reference".

CMP beans use EJB QL for database access. See Appendix G, "EJB Query Language (EJB-QL) and WebLogic Server."

Container-managed persistence offers these advantages:

  • Reduced programming effort—You do not write methods to perform database access for a CMP bean. The EJB container generates the methods automatically.

  • Increased portability—CMP increases bean portability in these ways:

    • De-coupling physical database details from business logic makes a bean logically independent of the associated database. If you implement a modified database design, or change to a different database server, you do not have to modify bean code.

    • You can redeploy the bean on a different Java EE application server without modifying or recompiling bean code.


      Note:

      If you redeploy a bean that uses features that are not supported by the target application server, changes to the bean code might be necessary.

For more information on features supported by CMP entities, see Entity EJBs.

Use Bean-Managed Persistence (BMP) Only When Necessary

A bean that manages its own persistence must contain the methods that perform data access.

BMP is not encouraged—CMP offers many advantages over bean-managed persistence, as described in Use Container-Managed Persistence (CMP) for Productivity and Portability.

However, some application requirements cannot be satisfied by CMP beans. For instance, you must use BMP if:

  • Your application must use an existing library of stored SQL procedures.

  • The target database does not support JDBC.

  • There is complex mapping between the bean and database tables. For instance, the bean maps multiple tables that do not share a primary key.

Transaction Design and Management Options

A transaction is a unit of work that changes application state—whether on disk, in memory or in a database—that, once started, is completed entirely, or not at all.

Understanding Transaction Demarcation Strategies and Performance

Transactions can be demarcated—started, and ended with a commit or rollback—by the EJB container, by bean code, or by client code.

Demarcating Transactions at the Server Level is Most Efficient

Transactions are costly application resources, especially database transactions, because they reserve a network connection for the duration of the transaction. In a multi-tiered architecture—with database, application server, and Web layers—you optimize performance by reducing the network traffic "round trip." The best approach is to start and stop transactions at the application server level, in the EJB container.

Container-Managed Transactions Are Simpler to Develop and Perform Well

Container-managed transactions (CMTs) are supported by all bean types: session, entity, and message-driven. They provide good performance, and simplify development because the enterprise bean code does not include statements that begin and end the transaction.

Each method in a CMT bean can be associated with a single transaction, but does not have to be. In a container-managed transaction, the EJB container manages the transaction, including start, stop, commit, and rollback. Usually, the container starts a transaction just before a bean method starts, and commits it just before the method exits.

For information about the elements related to transaction management in ejb-jar.xml and weblogic-ejb-jar.xml, see Container-Managed Transactions Elements.

Rollback

If an exception is thrown during a transaction, the container will automatically roll back the transaction. You can configure the EJB container to automatically retry container-managed transactions that have rolled back, provided the transactions did not roll back as the result of system exception-based errors. You can also explicitly program rollbacks in your bean. For more information see Chapter 4, "Implementing Enterprise JavaBeans."

Transaction Boundaries

You control how the EJB container manages the transaction boundaries when delegating a method invocation to an enterprise bean's business method for different invocation scenarios, with the trans-attribute element in ejb-jar.xml.

For example, if the client calling a transaction is itself running in a transaction, the trans-attribute element for the called transaction determines whether it will run in a new transaction or within the calling transaction.

Distributing Transactions Across Beans

A single database transaction can span multiple beans, on multiple servers instances. For information about implementing transactions that involve more than one bean, see Programming Transactions That Are Distributed Across EJBs.

Costly Option: Distributing Transactions Across Databases

Transactions that update multiple datastores must commit or roll back as a logical unit. The two-phase commit protocol is a method of coordinating a single transaction across multiple resource managers to ensure that updates are committed in all participating databases, or are fully rolled back out of all the databases.

Two-phase commit is resource-intensive. Avoid distributing transactions across databases.

Bean-Level Transaction Management

In a bean-managed transaction, the EJB code manages the transaction, including start, stop, commit, and rollback. Bean-managed transactions are supported by all session and message-driven beans; you cannot use bean-managed transactions with entity beans.


Note:

Bean-managed transactions cannot use container-provided transaction management features. Do not combine bean-managed and container-managed transactions in the same bean.

When to Use Bean-Managed Transactions

These are examples of requirements that may dictate the use of bean-managed transactions:

  • You need to define multiple transactions with a single method call. With container-managed transactions, a method can only be associated with a single transaction. You can use a bean-managed transaction to define multiple transactions with a single method. However, consider avoiding the need for a bean-managed transaction by breaking the method in to multiple methods, each with its own container-managed transaction.

  • You need to define a single transaction that spans multiple EJB method calls. For example, a stateful session EJB that uses one method to begin a transaction, and another method to commit or roll back a transaction.

    Try to avoid this practice, because it requires detailed information about the workings of the EJB object. However, if this scenario is required, you must use bean-managed transaction coordination, and you must coordinate client calls to the respective methods.

Keep Bean-Managed Transactions Short

To simplify development, and improve reliability, keep bean-managed transactions reasonably short.

For information about implementing bean-managed transactions, see Programming Bean-Managed Transactions.

Client-Level Transaction Management is Costly

Client applications are subject to interruptions or unexpected terminations. If you start and stop a transaction at the client level, you risk:

  • Consumption of network resources during waits for user actions, interruptions, until resumption of client activity or timeout.

  • Consumption of processing resources and network resources to rollback the transaction after timeout or termination of the transaction.

Do not manage transactions in client applications unless there are overriding reasons to do so.

Transaction Isolation: A Performance vs. Data Consistency Choice

A transaction's isolation level is the degree to which it exposes updated but uncommitted data to other transactions. Allowing access to uncommitted data can improve performance, but increases the risk of incorrect data being supplied to other transactions.

Set the isolation level for bean-managed transactions in the bean's Java code. For instructions, see Programming Bean-Managed Transactions.

Set the isolation level for container-managed transactions in the isolation-level sub-element of the transaction-isolation element of weblogic-ejb-jar.xml. WebLogic Server passes this value to the underlying database. The behavior of the transaction depends both on the EJB's isolation level setting and the concurrency control of the underlying persistent store.

For more information on setting container-managed transaction isolation levels, see Programming JTA for Oracle WebLogic Server.

Satisfying Application Requirements with WebLogic Server EJBs

WebLogic Server offers a variety of value-added features for enterprise beans that you can configure to meet the requirements of your application. They are described in WebLogic Server Value-Added EJB Features.

Table 3-2 cross references requirement types with topics that describe design strategies and WebLogic Server features you can use to satisfy your application requirements.

Table 3-2 Features and Design Patterns

When designing for...Consider these design patterns and WebLogic Server features...

Availability and reliability

Scalability


Data Consistency

Developer and Administrator Productivity


Performance

Choosing bean types and design patterns:

Clustering features:

Pooling and caching:

Transaction management:


PKPK;wEOEBPS/ejb_jar_ref.htm weblogic-ejb-jar.xml Deployment Descriptor Reference

B weblogic-ejb-jar.xml Deployment Descriptor Reference

The following sections describe the elements in the WebLogic-specific deployment descriptor, weblogic-ejb-jar.xml. In this release of WebLogic Server, weblogic-ejb-jar.xml is XML Schema-based (XSD). In prior releases, weblogic-ejb-jar.xml was Document Type Definition-based (DTD). For backward compatibility, this release of WebLogic Server supports XSD- or DTD-based EJB descriptors. In this release of WebLogic Server, the EJB container still supports all older DTD-based descriptors; you can deploy applications that use DTD-based descriptors in this release of WebLogic Server without modifying the descriptors.

For information on:

See the complete weblogic-ejb-jar.xsd schema at http://www.oracle.com/technology/weblogic/weblogic-ejb-jar/1.2/weblogic-ejb-jar.xsd.

2.1 weblogic-ejb-jar.xml File Structure

The WebLogic Server weblogic-ejb-jar.xml deployment descriptor file describes the elements that are unique to WebLogic Server.

The top level elements in the WebLogic Server weblogic-ejb-jar.xml are as follows:

  • description

  • weblogic-enterprise-bean

    • ejb-name

    • entity-descriptor | stateless-session-descriptor | stateful-session-descriptor | message-driven-descriptor

    • transaction-descriptor

    • iiop-security-descriptor

    • enable-call-by-reference

    • network-access-point

    • clients-on-same-server

    • run-as-principal-name

    • create-as-principal-name

    • remove-as-principal-name

    • passivate-as-principal-name

    • jndi-name

    • local-jndi-name

    • dispatch-policy

    • remote-client-timeout

    • stick-to-first-server

  • security-role-assignment

  • run-as-role-assignment

  • security-permission

  • transaction-isolation

  • message-destination-descriptor

  • idempotent-methods

  • retry-methods-on-rollback

  • enable-bean-class-redeploy

  • timer-implementation

  • disable-warning

  • work-manager

  • component-factory-class-name

  • weblogic-compatibility

2.1 weblogic-ejb-jar.xml Elements

The following list of the elements in weblogic-ejb-jar.xml includes all elements that are supported in this release of WebLogic Server.

allow-concurrent-calls

Range of values: True | False

Default value: False

Parent elements:

  • weblogic-enterprise-bean

  • stateful-session-descriptor

Function

Specifies whether a stateful session bean instance allows concurrent method calls. By default, allows-concurrent-calls is False, in accordance with the EJB specification, and WebLogic Server will throw a RemoteException when a stateful session bean instance is currently handling a method call and another (concurrent) method call arrives on the server.

When this value is set to True, the EJB container blocks the concurrent method call and allows it to proceed when the previous call has completed.

allow-remove-during-transaction

Range of values: True | False

Default value: False

Parent elements:

weblogic-enterprise-bean
  stateful-session-descriptor

Function

Specifies that the remove method on a stateful session bean can be invoked within a transaction context.


Note:

Stateful session beans implementing the Synchronization interface should not use this tag and then call remove before the transaction ends. If this is done the EJB container will not invoke the synchronization callbacks.

cache-between-transactions

Range of values: True | False

Default value: False

Parent elements:

weblogic-enterprise-bean
  entity-descriptor
    entity-cache or entity cache-ref

Function

Formerly the db-is-shared element, specifies whether the EJB container will cache the persistent data of an entity bean across (between) transactions.

Specify True to enable the EJB container to perform long term caching of the data. Specify False to enable the EJB container to perform short term caching of the data.

A Read-Only bean ignores the value of the cache-between-transactions element because WebLogic Server always performs long term caching of Read-Only data.

See Limiting Database Reads with cache-between-transactions for more information.

Example

See persistence.

cache-type

Range of values: NRU | LRU

Default value: NRU

Parent elements:

weblogic-enterprise-bean
  stateful-session-cache

Function

Specifies the order in which EJBs are removed from the cache. The values are:

  • Least recently used (LRU)

  • Not recently used (NRU)

    The minimum cache size for NRU is 8. If max-beans-in-cache is less than 8, WebLogic Server uses a value of 8 for max-beans-in-cache.

Example

<stateful-session-cache>
    <cache-type>NRU</cache-type>
</stateful-session-cache>

client-authentication

Range of values: none | supported | required

Default value: n/a

Parent elements:

weblogic-enterprise-bean
  iiop-security-descriptor

Function

Specifies whether the EJB supports or requires client authentication.

client-cert-authentication

Range of values: none | supported | required

Default value: n/a

Parent elements:

weblogic-enterprise-bean
  iiop-security-descriptor
    transport-requirements

Function

Specifies whether the EJB supports or requires client certificate authentication at the transport level.

clients-on-same-server

Range of values: True | False

Default value: False

Parent element:

weblogic-enterprise-bean

Function

Determines whether WebLogic Server sends JNDI announcements for this EJB when it is deployed. When this attribute is False (the default), a WebLogic Server cluster automatically updates its JNDI tree to indicate the location of this EJB on a particular server. This ensures that all clients can access the EJB, even if the client is not collocated on the same server.

You can set clients-on-same-server to True when you know that all clients that will access this EJB will do so from the same server on which the bean is deployed. In this case, a WebLogic Server cluster does not send JNDI announcements for this EJB when it is deployed. Because JNDI updates in a cluster utilize multicast traffic, setting clients-on-same-server to True can reduce the startup time for very large clusters.

See "Optimization for Collocated Objects" in Using Clusters for Oracle WebLogic Server for more information on collocated EJBs.

Example

<weblogic-enterprise-bean>
    <ejb-name>AccountBean</ejb-name>
    ...
    <clients-on-same-server>True</clients-on-same-server>
</weblogic-enterprise-bean>

component-factory-class-name

Range of values: N/A

Default value: null

Parent element:

weblogic-ejb-jar

Function

Enable the Spring extension by setting this element to org.springframework.jee.interfaces.SpringComponentFactory. This element exists in EJB, Web, and application descriptors. A module-level descriptor overwrites an application-level descriptor. If the tag is set to null (default), the Spring extension is disabled.

concurrency-strategy

Range of values: Exclusive | Database | ReadOnly | Optimistic

Default value: Database

Parent elements:

weblogic-enterprise-bean
  entity-descriptor
    entity-cache

Or

weblogic-enterprise-bean
  entity-descriptor
    entity-cache-ref

Function

Specifies how the container should manage concurrent access to an entity bean. Set this element to one of four values:

  • Exclusive causes WebLogic Server to place an exclusive lock on cached entity EJB instances when the bean is associated with a transaction. Other requests for the EJB instance are blocked until the transaction completes. This option was the default locking behavior for WebLogic Server 3.1 through 5.1.

  • Database causes WebLogic Server to defer locking requests for an entity EJB to the underlying datastore. With the Database concurrency strategy, WebLogic Server allocates a separate entity bean instance and allows locking and caching to be handled by the database. This is the default option.

  • ReadOnly is used for read-only entity beans. Activates a new instance for each transaction so that requests proceed in parallel. WebLogic Server calls ejbLoad() for ReadOnly beans are based on the read-timeout-seconds parameter.

  • Optimistic holds no locks in the EJB container or database during a transaction. The EJB container verifies that none of the data updated by a transaction has changed before committing the transaction. If any updated data changed, the EJB container rolls back the transaction.


    Note:

    When a cluster member updates a bean with a concurrency-strategy of Optimistic that is deployed to a cluster, the EJB container attempts to invalidate all copies of the bean in all servers in the cluster. You can disable this behavior by setting cluster-invalidation-disabled in weblogic-cmp-jar.xml to True. For more information, see Invalidation Options for Optimistic Concurrency in Clusters.

See Choosing a Concurrency Strategy for more information on the Exclusive and Database locking behaviors. See Read-Write versus Read-Only Entity Beans for more information about read-only entity EJBs.

Example

<weblogic-enterprise-bean>
    <ejb-name>AccountBean</ejb-name>
    <entity-descriptor>
        <entity-cache>
            <concurrency-strategy>ReadOnly</concurrency-strategy>
        </entity-cache>
    </entity-descriptor>
</weblogic-enterprise-bean>

confidentiality

Range of values: none | supported | required

Default value: n/a

Parent elements:

weblogic-enterprise-bean
  iiop-security-descriptor
    transport-requirements

Function

Specifies the transport confidentiality requirements for the EJB. Using the confidentiality element ensures that the data is sent between the client and server in such a way as to prevent other entities from observing the contents.

connection-factory-jndi-name

Range of values: Valid JNDI name

Default value: If not specified, the default is weblogic.jms.MessageDrivenBeanConnectionFactory, which must have been declared in the JMSConnectionFactory element in config.xml.

Parent elements:

weblogic-enterprise-bean
  message-driven-descriptor

Function

Specifies the JNDI name of the JMS Connection Factory that a message-driven EJB looks up to create its queues and topics. See "Configuring MDBs for Destinations" and "How to Set connection-factory-jndi-name" in

Example

<message-driven-descriptor>
    <connection-factory-jndi-name>
    java:comp/env/jms/MyConnectionFactory
    </connection-factory-jndi-name>
</message-driven-descriptor>

connection-factory-resource-link

Range of values: Valid resource within a JMS module

Default value: n/a.

Parent elements:

weblogic-enterprise-bean
  message-destination-descriptor

Function

Maps to a resource within a JMS module defined in ejb-jar.xml to an actual JMS Module Reference in WebLogic Server.

create-as-principal-name

Range of values: Valid principal name

Default value: n/a

Parent element:

weblogic-enterprise-bean

Function

Introduced in WebLogic Server 8.1 SP01, specifies the principal to be used in situations where ejbCreate would otherwise run with an anonymous principal. Under such conditions, the choice of which principal to run as is governed by the following rule:

if create-as-principal-name is set

then use that principal

else

If a run-as role has been specified for the bean in ejb-jar.xml

then use a principal according to the rules for setting the run-as-role-assignment

else

run ejbCreate as an anonymous principal.

The create-as-principal-name element only needs to be specified if operations within ejbCreate require more permissions than the anonymous principal would have.

This element effects the ejbCreate methods of stateless session beans and message-driven beans.

See also remove-as-principal-name, passivate-as-principal-name, and principal-name.

delay-updates-until-end-of-tx

Range of values: True | False

Default value: True

Parent elements:

weblogic-enterprise-bean
  entity-descriptor
    persistence

Function

Set the delay-updates-until-end-of-tx element to True (the default) to update the persistent store of all beans in a transaction at the completion of the transaction. This setting generally improves performance by avoiding unnecessary updates. However, it does not preserve the ordering of database updates within a database transaction.

If your datastore uses an isolation level of TransactionReadUncommitted, you may want to allow other database users to view the intermediate results of in-progress transactions. In this case, set delay-updates-to-end-of-tx to False to update the bean's persistent store at the conclusion of each method invoke. See Understanding ejbLoad() and ejbStore() Behavior for more information.


Note:

Setting delay-updates-until-end-of-tx to False does not cause database updates to be "committed" to the database after each method invoke; they are only sent to the database. Updates are committed or rolled back in the database only at the conclusion of the transaction.

Example

<entity-descriptor>
    <persistence>
    ...
    ...
    <delay-updates-until-end-of-tx>False</delay-updates-until-end-of-tx>
    </persistence>
</entity-descriptor>

description

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-ejb-jar

and

weblogic-ejb-jar
  transaction-isolation
    method

and

weblogic-ejb-jar
  idempotent-methods
    method

and

weblogic-ejb-jar
  retry-methods-on-rollback

Function

Describes the parent element.

Example

<description>Contains a description of parent element</description>

destination-jndi-name

Range of values: Valid JNDI name

Default value: n/a

Parent elements:

weblogic-enterprise-bean
  message-destination-descriptor

and

weblogic-enterprise-bean
  message-driven-descriptor

Function

Specifies the JNDI name used to associate a message-driven bean with an actual JMS Queue or Topic deployed in the WebLogic Server JNDI tree.

destination-resource-link

Range of values: Valid resource within a JMS module

Default value: n/a

Parent elements:

weblogic-enterprise-bean
  message-destination-descriptor

Function

Maps to a resource within a JMS module defined in ejb-jar.xml to an actual JMS Module Reference in WebLogic Server.

disable-warning

Range of values: BEA-010001 | BEA-010054 | BEA-010200 | BEA-010202

Default value: n/a

Parent element:

weblogic-ejb-jar

Function

Specifies that WebLogic Server should disable the warning message whose ID is specified. Set this element to one of four values:

  • BEA-010001—Disables this warning message: "EJB class loaded from system classpath during deployment."

  • BEA-010054—Disables this warning message: "EJB class loaded from system classpath during compilation."

  • BEA-010200—Disables this warning message: "EJB impl class contains a public static field, method or class."

  • BEA-010202—Disables this warning message: "Call-by-reference not enabled."

Example

To disable the warning message: "Call-by-reference not enabled", set <disable-warning>, as shown below.

<disable-warning>BEA-010202</disable-warning>

dispatch-policy

Range of values: Valid execute queue name

Default value: n/a

Parent element:

weblogic-enterprise-bean

Function

Designates which server execute thread pool the EJB should run in. Dispatch polices are supported for all types of beans, including entity, session, and message-driven.

If no dispatch-policy is specified, or the specified dispatch-policy refers to a nonexistent server execute thread pool, then the server's default execute thread pool is used instead.

WebLogic Server ignores dispatch-policy if the host server instance does not have an execute thread queue bearing a corresponding name.

If a message-driven bean (MDB) is driven by a foreign (non-WebLogic) destination source, WebLogic Server might ignore dispatch-policy, as the MDB may instead run in the foreign provider's threading mechanism. For example, for the IBM WebSphere MQSeries messaging software, dispatch-policy is not honored for non-transactional queues; instead the application code runs in an MQSeries thread. For MQSeries transactional queues, and both non-transactional and transactional topics, dispatch-policy is honored.

The maximum number of concurrently running MDB instances is designated by a combination of max-beans-in-free-pool and dispatch-policy values. See "MDB Thread Management" in Performance and Tuning for Oracle WebLogic Server.

Example

<dispatch-policy>queue_name</dispatch-policy>

distributed-destination-connection

Range of values: LocalOnly | EveryMember

Default value: LocalOnly

Parent elements:

weblogic-ejb-jar
  weblogic-enterprise-bean
    message-driven-descriptor

Function


Note:

This element is valid for WebLogic JMS 9.0 or later.

Specifies whether an MDB that accesses a WebLogic JMS distributed queue in the same cluster consumes from all distributed destination members or only those members local to the current Weblogic Server.

Valid values include:

  • LocalOnly—Deployment descriptor and message-driven bean are in the same cluster.

  • EveryMember—Deployment descriptor is on a remote server.

If set to EveryMember, the total number of connections will be equal to: (the number of servers where message-driven bean is deployed) x (the number of destinations). For larger deployments, the number of connections may consume a considerable amount of resources.

The EveryMember setting incurs additional network and CPU overhead transferring messages from remote servers to the local MDB; it is normally only recommended for limited use cases (such as MDBs with JMS selector filters that are unique to the current server).

Example

<distributed-destination-connection>EveryMember</distributed-destination-connection>

durable-subscription-deletion

Range of values: True | False

Default value: False

Parent elements:

weblogic-ejb-jar
  weblogic-enterprise-bean
    message-driven-descriptor

Function

Indicates whether you want durable topic subscriptions to be automatically deleted when an MDB is undeployed or removed.

Example

<durable-subscription-deletion>True</durable-subscription-deletion>

ejb-name

Range of values: Name, which conforms to the lexical rules for an NMTOKEN, of an EJB that is defined in ejb-jar.xml

Default value: n/a

Parent elements:

weblogic-enterprise-bean

and

weblogic-enterprise-bean
  method

Function

Specifies an enterprise bean's name, using the same name for the bean that is specified in ejb-jar.xml. The enterprise bean code does not depend on the name; therefore the name can be changed during the application assembly process without breaking the enterprise bean's function. There is no architected relationship between the ejb-name in the deployment descriptor and the JNDI name that the Deployer will assign to the enterprise bean's home.


Note:

Not recommended in weblogic-enterprise-bean. For more information, see Using EJB Links.

Example

See method.

ejb-reference-description

Range of values: n/a

Default value: n/a

Parent element:

weblogic-enterprise-bean

Function

Maps the JNDI name of an EJB in WebLogic Server to the name by which it is specified in the ejb-ref-name element in ejb-jar.xml.

Example

<ejb-reference-description>
    <ejb-ref-name>AdminBean</ejb-ref-name>
    <jndi-name>payroll.AdminBean</jndi-name>
</ejb-reference-description>

ejb-ref-name

Range of values: Valid ejb-ref-name specified in the associated ejb-jar.xml file

Default value: n/a

Parent elements:

weblogic-enterprise-bean
  ejb-reference-description

Function

Specifies a resource reference name. This element is the reference that the EJB provider places within the ejb-jar.xml deployment file.

Example

<ejb-reference-description>
    <ejb-ref-name>AdminBean</ejb-ref-name>
    <jndi-name>payroll.AdminBean</jndi-name>
</ejb-reference-description>

enable-bean-class-redeploy

Range of values: True | False

Default value: False

Parent element:

weblogic-enterprise-jar

Function

By default, the EJB implementation class is loaded in the same classloader as the rest of the EJB classes. When the enable-bean-class-redeploy element is enabled, the implementation class, along with its super classes, gets loaded in a child classloader of the EJB module classloader. This allows the EJB implementation class to be redeployed without redeploying the entire EJB module.

There are some potential problems with loading the bean class in a child classloader. First, the bean class will no longer be visible to any classes loaded in the parent classloader, so those classes cannot refer to the bean class or errors will occur. Also, the bean class will not be able to invoke any package protected methods on any classes loaded in a different classloader. So, if your bean class invokes a helper class in the same package, the helper class methods must be declared public or IllegalAccessErrors will result.


Note:

This element is deprecated for EJB 3.0. Starting with WebLogic Server 10.3.0, you can replace this feature with FastSwap. See "Using FastSwap Deployment to Minimize Redeployment" in Deploying Applications to Oracle WebLogic Server.

Example

The following XML element enables redeployment of an individual bean class:

<enable-bean-class-redeploy>True</enable-bean-class-redeploy>

enable-call-by-reference

Range of values: True | False

Default value: False

Parent element:

weblogic-enterprise-bean

Function

When enable-call-by-reference is False, parameters to the EJB methods are copied—or passed by value—regardless of whether the EJB is called remotely or from within the same EAR.

When enable-call-by-reference is True, EJB methods called from within the same EAR file or standalone JAR file will pass arguments by reference. This improves the performance of method invocation since parameters are not copied.


Note:

Method parameters are always passed by value when an EJB is called remotely.

Example

<weblogic-enterprise-bean>
    <entity-descriptor>
        <ejb-name>AccountBean</ejb-name>
        ...
        <enable-call-by-reference>False</enable-call-by-reference>
    </entity-descriptor>
</weblogic-enterprise-bean>

enable-dynamic-queries

Range of values: True | False

Default value: True

Parent elements:

weblogic-enterprise-bean
  entity-descriptor

Function

Set to True to enable dynamic queries. Dynamic queries are only available for use with EJB 2.x CMP beans.

Example

<enable-dynamic-queries>True</enable-dynamic-queries>

entity-always-uses-transaction

Range of values: True | False

Default value: False

Parent elements:

weblogic-ejb-jar
  weblogic-compatibility

Function

This element, introduced in WebLogic Server 9.0, allows you to specify whether an entity bean must always use a transaction. Before WebLogic Server 9.0, when an entity bean ran in an unspecified transaction, the EJB container would create a transaction for the entity bean. Now, the EJB container no longer creates a transaction when an entity bean runs in an unspecified transaction. To disable this behavior and cause the EJB container to create a transaction for entity beans that run in unspecified transaction, set the value of this element to True.

entity-cache

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-enterprise-bean
  entity-descriptor

Function

Defines the following options used to cache entity EJB instances within WebLogic Server:

  • max-beans-in-cache

  • idle-timeout-seconds

  • read-timeout-seconds

  • concurrency-strategy

See Understanding Entity Caching for more information.

Example

<entity-descriptor>
    <entity-cache>
        <max-beans-in-cache>...</max-beans-in-cache>
        <idle-timeout-seconds>...</idle-timeout-seconds>
        <read-timeout-seconds>...<read-timeout-seconds>
        <concurrency-strategy>...</concurrency-strategy>
    </entity-cache>
    <persistence>...</persistence>
    <entity-clustering>...</entity-clustering>
</entity-descriptor>

entity-cache-name

Range of values: Name assigned to an application level entity cache in the weblogic-application.xml file

Default value: n/a

Parent elements:

weblogic-enterprise-bean
  entity-descriptor
    entity-cache-ref

Function

Refers to an application level entity cache that the entity bean uses. An application level cache is a cache that may be shared by multiple entity beans in the same application. The value you specify for entity-cache-name must match the name assigned to an application level entity cache in the weblogic-application.xml file.

For more information about the weblogic-application.xml file, see "Enterprise Application Deployment Descriptor Elements" in Deploying Applications to Oracle WebLogic Server.

Example

See entity-cache-ref.

entity-cache-ref

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-enterprise-bean
  entity-descriptor

Function

Refers to an application level entity cache which can cache instances of multiple entity beans that are part of the same application. Application level entity caches are declared in the weblogic-application.xml file.

Use concurrency-strategy to define the type of concurrency you want the bean to use. The concurrency-strategy must be compatible with the application level cache's caching strategy. For example, an Exclusive cache only supports beans with a concurrency-strategy of Exclusive. A MultiVersion cache supports the Database, ReadOnly, and Optimistic concurrency strategies.

Example

<entity-cache-ref>
    <entity-cache-name>AllEntityCache</entity-cache-name>
    <read-timeout-seconds>600</read-timeout-seconds>
    <cache-between-transactions>true</cache-between-transactions>
    <concurrency-strategy>ReadOnly</concurrency-strategy>
    <estimated-bean-size>20</estimated-bean-size>
</entity-cache-ref>

entity-clustering

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-enterprise-bean
  entity-descriptor

Function

Specifies how an entity bean will be replicated in a WebLogic cluster:

  • home-is-clusterable

  • home-load-algorithm

  • home-call-router-class-name

  • use-serverside-stubs

Example

<entity-clustering>
    <home-is-clusterable>True</home-is-clusterable>
    <home-load-algorithm>random</home-load-algorithm>
    <home-call-router-class-name>beanRouter</home-call-router-class-name>
    <use-serverside-stubs>True</use-serverside-stubs>
</entity-clustering>

entity-descriptor

Range of values: n/a

Default value: n/a

Parent element:

weblogic-enterprise-bean

Function

Specifies the following deployment parameters that are applicable to an entity bean:

  • pool

  • timer-descriptor

  • entity-cache or entity-cache-ref

  • persistence

  • entity-clustering

  • invalidation-target

  • enable-dynamic-queries

Example

<entity-descriptor>
    <pool>...</pool>
    <timer-descriptor>...</timer-descriptor>
    <entity-cache>...</entity-cache>
    <persistence>...</persistence>
    <entity-clustering>...</entity-clustering>
    <invalidation-target>...</invalidation-target>
    <enable-dynamic-queries>...</enable-dynamic-queries>
</entity-descriptor>

estimated-bean-size

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-enterprise-bean
  entity-descriptor

Function

Specifies the estimated average size of the instances of an entity bean in bytes. This is the average number of bytes of memory that is consumed by each instance.

Use the estimated-bean-size element when the application level cache you use to cache beans is also specified in terms of bytes and megabytes.

Although you may not know the exact number of bytes consumed by the entity bean instances, specifying a size allows you to give some relative weight to the beans that share a cache at one time.

For example, suppose bean A and bean B share a cache, called AB-cache, that has a size of 1000 bytes and the size of A is 10 bytes and the size of B is 20 bytes, then the cache can hold at most 100 instances of A and 50 instances of B. If 100 instances of A are cached, this implies that 0 instances of B are cached.

Example

See entity-cache-ref.

externally-defined

Range of values: True | False

Default value: none

Parent elements:

weblogic-ejb-jar
  security-role-assignment

Function

Indicates that a particular security role is defined externally in a security realm, outside of the deployment descriptor. Because the security role and its principal-name mapping is defined elsewhere, principal-names are not to be specified in the deployment descriptor. This tag is used as an indicative placeholder instead of a set of principal-name elements. Use this element instead of global-role, which has been deprecated and was removed from WebLogic Server in release 9.0.

finders-load-bean

Range of values: True | False

Default value: True

Parent elements:

weblogic-enterprise-bean
  entity-descriptor
    persistence

Function

Valid only for CMP entity EJBs. The finders-load-bean element determines whether WebLogic Server loads the EJB into the cache after a call to a finder method returns a reference to the bean. If you set this element to True, WebLogic Server immediately loads the bean into the cache if a reference to a bean is returned by the finder. If you set this element to False, WebLogic Server does not automatically load the bean into the cache until the first method invocation; this behavior is consistent with the EJB 1.1 specification.

Example

<entity-descriptor>
    <persistence>
        <finders-load-bean>True</finders-load-bean>
    </persistence>
</entity-descriptor>

generate-unique-jms-client-id

Range of values: True | False

Default value: False

Parent elements:

weblogic-ejb-jar
  weblogic-enterprise-bean
    message-driven-descriptor

Function

Indicates whether or not you want the EJB container to generate a unique client-id for every instance of an MDB. Enabling this flag makes it easier to deploy durable MDBs to multiple server instances in a WebLogic Server cluster.

global-role

The global-role element is deprecated and was removed from WebLogic Server in release 9.0. Use the externally-defined element instead.

home-call-router-class-name

Range of values: Valid name of a custom class

Default value: n/a

Parent elements:

weblogic-enterprise-bean
  entity-descriptor
    entity-clustering

and

weblogic-enterprise-bean
  stateful-session-descriptor
    stateful-session-clustering

and

weblogic-enterprise-bean
  stateless-session-descriptor
    stateless-session-clustering

Function

Specifies the name of a custom class to use for routing bean method calls. This class must implement weblogic.rmi.cluster.CallRouter(). If specified, an instance of this class is called before each method call. The router class has the opportunity to choose a server to route to based on the method parameters. The class returns either a server name or null, which indicates that the current load algorithm should select the server.

home-is-clusterable

Range of values: True | False

Default value: True

Parent elements:

weblogic-enterprise-bean
  entity-descriptor
    entity-clustering

and

weblogic-enterprise-bean
  stateful-session-descriptor
    stateful-session-clustering

and

weblogic-enterprise-bean
  stateful-session-descriptor
    stateless-clustering

Function

When home-is-clusterable is True, the EJB can be deployed from multiple WebLogic Servers in a cluster. Calls to the home stub are load-balanced between the servers on which this bean is deployed, and if a server hosting the bean is unreachable, the call automatically fails over to another server hosting the bean.

Example

See entity-clustering.

home-load-algorithm

Range of values: round-robin | random | weight-based | RoundRobinAffinity | RandomAffinity | WeightBasedAffinity

Default value: Value of weblogic.cluster.defaultLoadAlgorithm

Parent elements:

weblogic-enterprise-bean
  entity-descriptor
    entity-clustering

and

weblogic-enterprise-bean
  stateful-session-descriptor
    stateful-session-clustering

and

weblogic-enterprise-bean
  entity-descriptor
    entity-clustering

Function

Specifies the algorithm to use for load balancing between replicas of the EJB home in a cluster. If this element is not defined, WebLogic Server uses the algorithm specified by the server element, weblogic.cluster.defaultLoadAlgorithm.

You can define home-load-algorithm as one of the following values:

  • round-robin—Load balancing is performed in a sequential fashion among the servers hosting the bean.

  • random—Replicas of the EJB home are deployed randomly among the servers hosting the bean.

  • weight-based—Replicas of the EJB home are deployed on host servers according to the servers' current workload.

  • round-robin-affinity—server affinity governs connections between external Java clients and server instances; round robin load balancing is used for connections between server instances.

  • weight-based-affinity—server affinity governs connections between external Java clients and server instances; weight-based load balancing is used for connections between server instances.

  • random-affinity—server affinity governs connections between external Java clients and server instances; random load balancing is used for connections between server instances.

For more information, see "Load Balancing for EJBs and RMI Objects" in Using Clusters for Oracle WebLogic Server.

idempotent-methods

Range of values: n/a

Default value: n/a

Parent element:

weblogic-ejb-jar

Function

Defines list of methods of a clustered EJB which are written in such a way that repeated calls to the same method with the same arguments has exactly the same effect as a single call. This allows the failover handler to retry a failed call without knowing whether the call actually compiled on the failed server. When you enable idempotent-methods for a method, the EJB stub can automatically recover from any failure as long as it can reach another server hosting the EJB.

Clustering must be enabled for the EJB. To enable clustering, see entity-clustering, stateful-session-clustering, and stateless-clustering.

The methods on stateless session bean homes and read-only entity beans are automatically set to be idempotent. It is not necessary to explicitly specify them as idempotent.

Example

<idempotent-method>
    <method>
        <description>...</description>
        <ejb-name>...</ejb-name>
        <method-intf>...</method-intf>
        <method-name>...</method-name>
        <method-params>...</method-params>
    </method>
</idempotent-method>

identity-assertion

Range of values: none | supported | required

Default value: none

Parent elements:

weblogic-enterprise-bean
  iiop-security-descriptor

Function

Specifies whether the EJB supports or requires identity assertion.

idle-timeout-seconds

Range of values: 1 to maxSeconds, where maxSeconds is the maximum value of an int

Default value: 600

Parent elements:

weblogic-enterprise-bean
  entity-descriptor
    entity-cache

and

weblogic-enterprise-bean
  entity-descriptor
    entity-cache-ref

and

weblogic-enterprise-bean
  stateful-session-descriptor
    stateful-session-cache

and

weblogic-enterprise-bean
  stateless-session-descriptor or message-driven-descriptor or entity-descriptor
    pool

Function

Defines the maximum length of time an EJB should remain in the cache. After this time has elapsed, WebLogic Server removes the bean instance if the number of beans in cache approaches the limit of max-beans-in-cache. The removed bean instances are passivated. See Caching and Passivating Stateful Session EJBs and Managing Entity Bean Pooling and Caching for more information.

Also defines the maximum length of time an EJB should remain idle in the free pool before it is removed. After this time has elapsed, WebLogic Server removes the bean instance from the free pool so long as doing so will not cause the number of beans in the pool to fall below the number specified in initial-beans-in-free-pool.


Note:

Although idle-timeout-seconds appears in the entity-cache element, WebLogic Server 8.1 SP1 and SP2 do not use its value in managing the life cycle of entity EJBs—in those service packs, idle-timeout-seconds has no effect on when entity beans are removed from cache.

Example

The following entry indicates that the stateful session EJB, AccountBean, should become eligible for removal if max-beans-in-cache is reached and the bean has been in cache for 20 minutes:

<weblogic-enterprise-bean>
    <ejb-name>AccountBean</ejb-name>
    <stateful-session-descriptor>
        <stateful-session-cache>
            <max-beans-in-cache>200</max-beans-in-cache>
            <idle-timeout-seconds>1200</idle-timeout-seconds>
        </stateful-session-cache>
    </stateful-session-descriptor>
</weblogic-enterprise-bean>

iiop-security-descriptor

Range of values: n/a

Default value: n/a

Parent element:

weblogic-enterprise-bean

Function

Specifies security configuration parameters at the bean level. These parameters determine the IIOP security information contained in the IOR.

Example

<iiop-security-descriptor>
    <transport-requirements>...</transport-requirements>
    <client-authentication>supported<client-authentication>
    <identity-assertion>supported</identity-assertion>
</iiop-security-descriptor>

init-suspend-seconds

Range of values: any integer

Default value: 5

Parent elements:

weblogic-enterprise-bean
  message-driven-descriptor

Function

Specifies the initial number of seconds to suspend an MDB's JMS connection when the EJB container detects a JMS resource outage. For more information, see "Configuring Suspension of Message Delivery During JMS Resource Outages" in Oracle Fusion Middleware Programming Message-Driven Beans for Oracle WebLogic Server.

initial-beans-in-free-pool

Range of values: 0 to maxBeans

Default value: 0

Parent elements:

weblogic-enterprise-bean
  stateless-session-descriptor or message-driven-descriptor or entity-descriptor
    pool

Function

If you specify a value for initial-beans-in-free-pool, you set the initial size of the pool. WebLogic Server populates the free pool with the specified number of bean instances for every bean class at startup. Populating the free pool in this way improves initial response time for the EJB, because initial requests for the bean can be satisfied without generating a new instance.

Example

See pool.

initial-context-factory

Range of values: Valid name of an initial context factory

Default value: weblogic.jndi.WLInitialContextFactory

Parent elements:

weblogic-enterprise-bean
  message-destination-descriptor

and

weblogic-enterprise-bean
  message-driven-descriptor

Function

Specifies the initial context factory used by the JMS provider to create initial context. See "Configuring MDBs for Destinations" and "How to Set initial-context-factory" in Oracle Fusion Middleware Programming Message-Driven Beans for Oracle WebLogic Server.

Example

<message-driven-descriptor>
    <initial-context-factory>fiorano.jms.rtl.FioranoInitialContextFactory
    </initial-context-factory>
</message-driven-descriptor>

See also message-destination-descriptor.

integrity

Range of values: none | supported | required

Default value: n/a

Parent elements:

weblogic-enterprise-bean
  iiop-security-descriptor
    transport-requirements

Function

Specifies the transport integrity requirements for the EJB. Using the integrity element ensures that the data is sent between the client and server in such a way that it cannot be changed in transit.

invalidation-target

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-enterprise-bean
  entity-descriptor

Function

Specifies a Read-Only entity EJB that should be invalidated when this container-managed persistence entity EJB has been modified.

The target ejb-name must be a Read-Only entity EJB and this element can only be specified for an EJB 2.x container-managed persistence entity EJB.

Example

<invalidation-target>
    <ejb-name>StockReaderEJB</ejb-name>
</invalidation-target>

is-modified-method-name

Range of values: Valid entity EJB method name

Default value: n/a

Parent elements:

weblogic-enterprise-bean
  entity-descriptor
    persistence

Function

Specifies a method that WebLogic Server calls when the EJB is stored. The specified method must return a boolean value. If no method is specified, WebLogic Server always assumes that the EJB has been modified and always saves it.

Providing a method and setting it as appropriate can improve performance for EJB 1.1-compliant beans, and for beans that use bean-managed persistence. However, any errors in the method's return value can cause data inconsistency problems.


Note:

isModified() is no longer required for 2.x CMP entity EJBs based on the EJB 2.x specification. However, it still applies to BMP and 1.1 CMP EJBs. When you deploy EJB 2.x entity beans with container-managed persistence, WebLogic Server automatically detects which EJB fields have been modified, and writes only those fields to the underlying datastore.

Example

<entity-descriptor>
    <persistence>
        <is-modified-method-name>semidivine</is-modified-method-name>
    </persistence>
</entity-descriptor>

isolation-level

Range of values: TransactionSerializable | TransactionReadCommitted | TransactionReadUncommitted | TransactionRepeatableRead | TransactionReadCommittedForUpdate | TransactionReadCommittedForUpdateNoWait

Default value: Default value of the underlying database

Parent elements:

weblogic-ejb-jar
  transaction-isolation

Function

Defines method-level transaction isolation settings for an EJB. Allowable values include:

  • TransactionSerializable—Simultaneously executing this transaction multiple times has the same effect as executing the transaction multiple times in a serial fashion.


    Note:

    For Oracle databases, Oracle recommends that you use the TransactionReadCommittedForUpdate isolation level instead of the TransactionSerializable isolation level. This is because Oracle databases do not lock read data at the TransactionSerializable isolation level. Additionally, at the TransactionSerializable isolation level, it is possible for concurrent transactions on Oracle databases to proceed without throwing the Oracle exception ORA-08177 "can't serialize access for this transaction"). For more information on the TransactionReadCommittedForUpdate isolation level, see Oracle Database-Only Isolation Levels.

  • TransactionReadCommitted—The transaction can view only committed updates from other transactions.

  • TransactionReadUncommitted—The transaction can view uncommitted updates from other transactions.

  • TransactionRepeatableRead—Once the transaction reads a subset of data, repeated reads of the same data return the same values, even if other transactions have subsequently modified the data.

Oracle Database-Only Isolation Levels

These addition values are supported only for Oracle databases, and only for container-managed persistence (CMP) EJBs:

  • TransactionReadCommittedForUpdate— Supported only for Oracle databases, for container-managed persistence (CMP) EJBs only. This value sets the isolation level to TransactionReadCommitted, and for the duration of the transaction, all SQL SELECT statements executed in any method are executed with FOR UPDATE appended to them. This causes the secluded rows to be locked for update. If the Oracle database cannot lock the rows affected by the query immediately, then it waits until the rows are free. This condition remains in effect until the transaction does a COMMIT or ROLLBACK.

    This isolation level can be used to avoid the error:

    java.sql.SQLException: ORA-08177: can't serialize access for this transaction

    which can (but does not always) occur when using the TransactionSerializable isolation level with Oracle databases.


    Note:

    For Oracle databases, Oracle recommends that you use this isolation level (TransactionReadCommittedForUpdate) instead of the TransactionSerializable isolation level. This is because Oracle databases do not lock read data at the TransactionSerializable isolation level.

  • TransactionReadCommittedForUpdateNoWait—Supported only for Oracle databases, for container-managed persistence (CMP) EJBs only.

    This value sets the isolation level to TransactionReadCommitted, and for the duration of the transaction, all SQL SELECT statements executed in any method are executed with FOR UPDATE NO WAIT appended to them. This causes the selected rows to be locked for update.

    In contrast to the TransactionReadCommittedForUpdate setting, TransactionReadCommittedForUpdateNoWait causes the Oracle DBMS to NOT WAIT if the required locks cannot be acquired immediately—the affected SELECT query will fail and an exception will be thrown by the container.

Refer to your database documentation for more information on support for different isolation levels.

jms-client-id

Range of values: n/a

Default value: ejb-name for the EJB

Parent element:

message-driven-descriptor

Function

Specifies a client ID for the MDB when it connects to a JMS destination. Required for durable subscriptions to JMS topics.

If you specify the connection factory that the MDB uses in connection-factory-jndi-name, the client ID can be defined in the ClientID element of the associated JMSConnectionFactory element in config.xml.

If JMSConnectionFactory in config.xml does not specify a ClientID, or if you use the default connection factory, (you do not specify connection-factory-jndi-name) the message-driven bean uses the jms-client-id value as its client id.

Example

<jms-client-id>MyClientID</jms-client-id>

jms-polling-interval-seconds

Range of values: n/a

Default value: 10 seconds

Parent element:

message-driven-descriptor

Function

Specifies the number of seconds between each attempt to reconnect to the JMS destination. Each message-driven bean listens on an associated JMS destination. If the JMS destination is located on another WebLogic Server instance or a foreign JMS provider, then the JMS destination may become unreachable. In this case, the EJB container automatically attempts to reconnect to the JMS Server. Once the JMS Server is up again, the message-driven bean can again receive messages.

Example

<jms-polling-interval-seconds>5</jms-polling-interval-seconds>

jndi-name

Range of values: Valid JNDI name

Default value: n/a

Parent elements:

weblogic-enterprise-bean

and

weblogic-enterprise-bean
  resource-description

and

weblogic-enterprise-bean
  ejb-reference-description

Function

Specifies the JNDI name of an actual EJB, resource, or reference available in WebLogic Server.


Note:

Assigning a JNDI name to a bean is not recommended. Global JNDI names generate heavy multicast traffic during clustered server startup. See Using EJB Links for the better practice. If you have an EAR library that contains EJBs, you cannot deploy multiple applications that reference the library because attempting to do so will result in a JNDI name conflict. This is because global JNDI name cannot be set for individual EJBs in EAR libraries; it can only be set for an entire library.

local-jndi-name

Range of values: Valid JNDI name

Default value: n/a

Parent elements:

weblogic-enterprise-bean

Function

JNDI name for a bean's local home. If a bean has both a remote and a local home, then it can be assigned two JNDI names; one for each home.


Note:

Assigning a JNDI name to a bean is not recommended. See Using EJB Links for the better practice.

Example

<local-jndi-name>weblogic.jndi.WLInitialContext
</local-jndi-name>

max-beans-in-cache

Range of values: 1 to maxBeans

Default value: 1000

Parent elements:

weblogic-enterprise-bean
  entity-descriptor
    entity-cache

and

weblogic-enterprise-bean
  stateful-session-descriptor
    stateful-session-cache

Function

Specifies the maximum number of objects of this class that are allowed in memory. When max-bean-in-cache is reached, WebLogic Server passivates some EJBs that have not recently been used by a client. max-beans-in-cache also affects when EJBs are removed from the WebLogic Server cache, as described in Caching and Passivating Stateful Session EJBs.

Example

<weblogic-enterprise-bean>
    <ejb-name>AccountBean</ejb-name>
    <entity-descriptor>
        <entity-cache>
            <max-beans-in-cache>200</max-beans-in-cache>
        </entity-cache>
    </entity-descriptor>
</weblogic-enterprise-bean>

max-beans-in-free-pool

Range of values: 0 to maxBeans

Default value: 1000

Parent elements:

weblogic-enterprise-bean
  stateless-session-descriptor
    pool

and

weblogic-enterprise-bean
  message-driven-descriptor
    pool

and

weblogic-enterprise-bean
  entity-descriptor
    pool

Function

WebLogic Server maintains a free pool of EJBs for every entity bean, stateless session bean, and message-driven bean class. The max-beans-in-free-pool element defines the size of this pool.

Example

See pool.

max-messages-in-transaction

Range of values: All positive integers

Default value: n/a

Parent elements:

weblogic-enterprise-bean
  message-driven-descriptor

Function

Specifies the maximum number of messages that can be in a transaction for this MDB.

max-queries-in-cache

Range of values: All positive integers

Default value: n/a

Parent elements:

weblogic-enterprise-bean
  entity-descriptor

Function

This element, introduced in WebLogic Server 9.0, specifies the maximum number of read-only entity queries to cache at the bean level. For information on caching read-only entity queries at the application level, see Using Query Caching (Read-Only Entity Beans).

max-suspend-seconds

Range of values: Any integer

Default value: 60

Parent elements:

weblogic-enterprise-bean
  message-driven-descriptor

Function

Specifies the maximum number of seconds to suspend an MDB's JMS connection when the EJB container detects a JMS resource outage. To disable JMS connection suspension when the EJB container detects a JMS resource outage, set the value of this element to 0. For more information, see "Configuring Suspension of Message Delivery During JMS Resource Outages" in Oracle Fusion Middleware Programming Message-Driven Beans for Oracle WebLogic Server.

message-destination-descriptor

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-enterprise-bean

Function

Maps a message destination reference in the ejb-jar.xml file to an actual message destination, such as a JMS Queue or Topic, in WebLogic Server.

Example

<message-destination-descriptor>
    <message-destination-name>...</message-destination-name>
    <destination-jndi-name>...</destination-jndi-name>
    <resource-link>...</resource-link>
    <initial-context-factory>...</initial-context-factory>
    <provider-url>...</provider-url>
</message-destination-descriptor>

message-destination-name

Range of values: A valid message destination reference name from the ejb-jar.xml file

Default value: n/a

Requirements: This element is required if the EJB specifies messages destination references in ejb-jar.xml.

Parent elements:

weblogic-enterprise-bean
  message-destination-descriptor

Function

Specifies the name of a message destination reference. This is the reference that the EJB provider places within the ejb-jar.xml deployment file.

message-driven-descriptor

Range of values: n/a

Default value: n/a

Parent element:

weblogic-enterprise-bean

Function

Associates a message-driven bean with a JMS destination in WebLogic Server.

Example

<message-driven-descriptor>
    <pool>...</pool>
    <timer-descriptor>...</timer-descriptor>
    <destination-jndi-name>...</destination-jndi-name>
    <initial-context-factory>...</initial-context-factory>
    <provider-url>...</provider-url>
    <connection-factory-jndi-name>...</connection-factory-jndi-name>
    <jms-polling-interval-seconds>...</jms-polling-interval-seconds>
    <jms-client-id>...</jms-client-id>
    <generate-unique-jms-client-id>...</generate-unique-jms-client-id>
    <durable-subscription-deletion>...</durable-subscription-deletion>
    <max-messages-in-transaction>...</max-messages-in-transaction>
    <distributed-destination-connection>...</distributed-destination-connection>
    <use81-style-polling>...</use81-style-polling>
    <init-suspend-seconds>...</init-suspend-seconds>
    <max-suspend-seconds>...</max-suspend-seconds>
</message-driven-descriptor>

method

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-ejb-jar
  transaction-isolation

and

weblogic-ejb-jar
  idempotent-methods

and

weblogic-ejb-jar
  retry-methods-on-rollback

Function

Defines a method or set of methods for an enterprise bean's home or remote interface.

Example

<method>
    <description>...</description>
    <ejb-name>...</ejb-name>
    <method-intf>...</method-intf>
    <method-name>...</method-name>
    <method-params>...</method-params>
</method>

method-intf

Range of values: Home | Remote | Local | Localhome

Default value: n/a

Parent elements:

weblogic-ejb-jar
  transaction-isolation
    method

and

weblogic-ejb-jar
  idempotent-methods
    method

Function

Specifies the EJB interface to which WebLogic Server applies isolation level properties, if the method has the same signature in multiple interfaces.

Example

See method.

method-name

Range of values: Name of an EJB defined in ejb-jar.xml | *

Default value: n/a

Parent elements:

weblogic-ejb-jar
  transaction-isolation
    method

and

weblogic-ejb-jar
  idempotent-methods
    method

Function

Specifies the name of an individual EJB method to which WebLogic Server applies isolation level properties. Use the asterisk (*) to specify all methods in the EJB's home and remote interfaces.

If you specify a method-name, the method must be available in the specified ejb-name.

Example

See method.

method-param

Range of values: Fully-qualified Java type name of a method parameter

Default value: n/a

Parent elements:

weblogic-ejb-jar
  transaction-isolation
    method
      method-params

and

weblogic-ejb-jar
  idempotent-methods
    method
      method-params

Function

Specifies the fully-qualified Java type name of a method parameter.

Example

See method-params.

method-params

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-ejb-jar
  transaction-isolation
    method

and

weblogic-ejb-jar
  idempotent-methods
    method

Function

Contains one or more elements that define the Java type name of each of the method's parameters.

Example

The method-params element contains one or more method-param elements, as shown here:

<method-params>
    <method-param>java.lang.String</method-param>
    ...
</method-params>

network-access-point

Range of values: Name of a custom network access point

Default value: n/a

Parent elements:

weblogic-enterprise-bean

Function

Assigns a custom network channel that the EJB will use for network communications. A network channel defines a set of connection attributes. For more information, see "Configuring Network Resources" in Configuring Server Environments for Oracle WebLogic Server.

Example

<weblogic-enterprise-bean>
    <network-access-point>SSLChannel</network-access-point>
</weblogic-enterprise-bean>

passivate-as-principal-name

Range of values: Valid WebLogic Server principal

Default value: n/a

Parent elements:

weblogic-enterprise-bean

Function

The passivate-as-principal-name element, introduced in WebLogic Server 8.1 SP01, specifies the principal to be used in situations where ejbPassivate would otherwise run with an anonymous principal. Under such conditions, the choice of which principal to run as is governed by the following rule:

If passivate-as-principal-name is set

then use that principal

else

if a run-as role has been specified for the bean in ejb-jar.xml

then use a principal according to the rules for setting the run-as-role-assignment

else

run ejbPassivate as an anonymous principal.

The passivate-as-principal-name element only needs to be specified if operations within ejbPassivate require more permissions than the anonymous principal would have.

This element affects the ejbPassivate methods of stateless session beans when passivation occurs due to a cache timeout.

See also remove-as-principal-name, create-as-principal-name, and principal-name.

persistence

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-enterprise-bean
  entity-descriptor

Function

Required only for entity EJBs that use container-managed persistence services. The persistence element defines the following options that determine the persistence type, transaction commit behavior, and ejbLoad() and ejbStore() behavior for entity EJBs in WebLogic Server:

  • is-modified-method-name

  • delay-updates-until-end-of-tx

  • finders-load-bean

  • persistence-use

Example

<entity-descriptor>
    <persistence>
        <is-modified-method-name>...</is-modified-method-name>
        <delay-updates-until-end-of-tx>...</delay-updates-until-end-of-tx>
        <finders-load-beand>...</finders-load-bean>
        <persistence-use>...</persistence-use>
    </persistence>
</entity-descriptor>

persistence-use

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-enterprise-bean
  entity-descriptor
    persistence

Function

Required only for entity EJBs that use container-managed persistence services. The persistence-use element stores an identifier of the persistence type to be used for this particular bean.

Example

<persistence-use>
    <type-identifier>WebLogic_CMP_RDBMS</type-identifier>
    <type-version>5.1.0</type-version>
    <type-storage>META-INF/weblogic-cmp-jar.xml</type-storage>
</persistence-use>

persistent-store-dir

Range of values: Valid file system directory

Default value: pstore

Parent elements:

weblogic-enterprise-bean
  stateful-session-descriptor

Function

Specifies a file system directory where WebLogic Server stores the state of passivated stateful session bean instances. For more information, see Specifying the Persistent Store Directory for Passivated Beans.

Example

<stateful-session-descriptor>
    <stateful-session-cache>...</stateful-session-cache>
    <allow-concurrent-calls>...</allow-concurrent-calls>
    <persistent-store-dir>MyPersistenceDir</persistent-store-dir>
    <stateful-session-clustering>...</stateful-session-clustering>
    <allow-remove-during-transaction>
</stateful-session-descriptor>

persistent-store-logical-name

Range of values: Valid name of a persistent store on the file system

Default value: n/a

Parent elements:

weblogic-enterprise-bean
  entity-descriptor
    timer-descriptor

and

weblogic-enterprise-bean
  message-driven-descriptor
    timer-descriptor

Function

Specifies the name of a persistent store on the server's file system where WebLogic Server stores timer objects. If you do not specify a persistent store name in this element, WebLogic Server stores timer objects in the default store.

pool

Range of values: n/a

Default value: n/a

Parent elements:

weblogic-enterprise-bean
  stateless-session-descriptor or message-driven-descriptor

and

  entity-descriptor

Function

Configures the behavior of the WebLogic Server free pool for entity EJBs, stateless session EJBs, and message-driven EJBs. The options are:

  • max-beans-in-free-pool

  • initial-beans-in-free-pool

  • idle-timeout-seconds

Example

<stateless-session-descriptor>
    <pool>
        <max-beans-in-free-pool>500</max-beans-in-free-pool>
        <initial-beans-in-free-pool>250</initial-beans-in-free-pool>
    </pool>
</stateless-session-descriptor>

principal-name

Range of values: Valid WebLogic Server principal name

Default value: n/a

Parent elements:

weblogic-ejb-jar
  security-role-assignment

Function

Specifies the name of an actual WebLogic Server principal to apply to the specified role-name. At least one principal-name is required in the security-role-assignment element. You may define more than one principal-name for each role-name.

provider-url

Range of values: Valid URL

Default value: t3://localhost:7001

Parent elements:

weblogic-enterprise-bean
  message-destination-descriptor

and

weblogic-enterprise-bean
  message-driven-descriptor

Function

Specifies the URL to be used by the InitialContext. See "Configuring MDBs for Destinations" and "How to Set provider-url" in Oracle Fusion Middleware Programming Message-Driven Beans for Oracle WebLogic Server.

Example

<message-driven-descriptor>
    <provider-url>WeblogicURL:Port</provider-url>
</message-driven-descriptor>

See also message-destination-descriptor.

read-timeout-seconds

Range of values: 0 to maxSeconds, where maxSeconds is the maximum value of an int

Default value: 600

Parent elements:

weblogic-enterprise-bean
  entity-descriptor
    entity-cache

or

weblogic-enterprise-bean
  entity-descriptor
    entity-cache-ref

Function

Specifies the number of seconds between ejbLoad() calls on a Read-Only entity bean. A value of 0 causes WebLogic Server to call ejbLoad() only when the bean is brought into the cache.

<