Programming WebLogic Enterprise JavaBeans
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weblogic-cmp-jar.xml Deployment Descriptor Reference
The following sections describe the EJB 2.0 deployment descriptor elements found in the weblogic-cmp-jar.xml file, the WebLogic-specific XML document type definitions (DTD) 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.
For information on the EJB 1.1 deployment descriptor elements see Important Information for EJB 1.1 Users.
- 2.0 weblogic-cmp-jar.xml Deployment Descriptor File Structure
- Changes to weblogic-cmp-jar.xml in WebLogic Server 8.1
- 2.0 weblogic-cmp-jar.xml Deployment Descriptor Elements
2.0 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 WebLogic Server Version 6.x.
You can continue to use the earlier weblogic-cmp-jar.xml DTD for EJB 1.1 beans that you will deploy on the WebLogic Server Version 8.1. However, if you want to use any of the new CMP 2.0 features, you must use the new DTD described below.
The top-level element of the WebLogic Server 8.1 weblogic-cmp-jar.xml consists of a weblogic-rdbms-jar stanza:
description
weblogic-version
weblogic-rdbms-jar
weblogic-rdbms-bean
ejb-name
data-source-name
table-map
field-group
relationship-caching
weblogic-query
delay-database-insert-until
automatic-key-generation
check-exists-on-method
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
Changes to weblogic-cmp-jar.xml in WebLogic Server 8.1
These changes were made to weblogic-cmp-jar.xml in WebLogic Server 8.1:
- enable-batch-operations was added in WebLogic Server 8.1.
- instance-lock-order was added in WebLogic Server 8.1 SP01.
- order-database-operations was added in WebLogic Server 8.1.
- serialize-byte-array-to-oracle-blob was added in WebLogic Server SP02.
- verify-rows was added in WebLogic Server 8.1.
2.0 weblogic-cmp-jar.xml Deployment Descriptor Elements
This list of the elements in weblogic-cmp-jar.xml includes all elements that were supported in any service pack of WebLogic Server 8.1. The previous section, Changes to weblogic-cmp-jar.xml in WebLogic Server 8.1 lists elements that were new, changed, or deprecated in Weblogic Server 8.1, or a subsequent service pack.
- allow-readonly-create-and-remove
- automatic-key-generation
- caching-element
- caching-name
- check-exists-on-method
- cmp-field
- cmr-field
- column-map
- create-default-dbms-tables
- database-type
- data-source-name
- db-cascade-delete
- dbms-column
- dbms-column-type
- default-dbms-tables-ddl
- delay-database-insert-until
- description
- ejb-name
- enable-batch-operations
- field-group
- field-map
- foreign-key-column
- foreign-key-table
- generator-name
- generator-type
- group-name
- include-updates
- instance-lock-order
- key-cache-size
- key-column
- lock-order
- max-elements
- method-name
- method-param
- method-params
- optimistic-column
- order-database-operations
- primary-key-table
- query-method
- relation-name
- relationship-caching
- relationship-role-map
- relationship-role-name
- serialize-byte-array-to-oracle-blob
- sql-select-distinct
- table-map
- table-name
- use-select-for-update
- validate-db-schema-with
- verify-columns
- verify-rows
- weblogic-ql
- weblogic-query
- weblogic-rdbms-bean
- weblogic-rdbms-jar
- weblogic-rdbms-relation
- weblogic-relationship-role
allow-readonly-create-and-remove
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 version 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
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 stanza for different primary key generation methods. For supported generation methods, see generator-type
Listing B-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>
Listing B-2 automatic-key-generation With generator-type=SQL-SERVER
<automatic-key-generation>
<generator-type>SQL-SERVER</generator-type>
</automatic-key-generation>
Listing B-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
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.
The caching-element stanza can contain nested caching element stanzas, as in the example shown in relationship-caching.
For information about relationship caching, see Relationship Caching.
Example
See relationship-caching:
caching-name
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
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>
cmp-field
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
Function
Specifies the name of a container-managed relationship field.
Example
<cmr-field>stock options</cmr-field>
column-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.
Note: The key-column element is not specified if the foreign-key-column refers to a remote bean.
Example
The XML stanza can contain the elements shown here:
<column-map
<foreign-key-column>account-id</foreign-key-column>
<key-column>id</key-column>
</column-map>
compatibility
Function
The <compatibility> stanza, 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>
<allow-readonly-create-and-remove>
</compatibility>
create-default-dbms-tables
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 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.
If TABLE CREATION fails, the server throws a Table Not Found error and the table must be created by hand.
See Automatic Table Creation (Development Only).
Automatic Oracle SEQUENCE Generation
Note: Automatic Oracle 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.
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The EJB container takes no action with respect to SEQUENCE generation. This is the default value. |
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The EJB container creates a SEQUENCE, and constructs its name by appending "_WL" to the value of the |
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The EJB container creates a SEQUENCE, and constructs its name by appending "_WL" to the value of the 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. |
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The EJB container creates a SEQUENCE, and constructs its name by appending "_WL" to the value of the 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. |
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The EJB container creates a SEQUENCE, and constructs its name by appending "_WL" to the value of the 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 SEQUENCE, see Support for Oracle SEQUENCE.
Example
The following example specifies the create-default-dbms-tables element.
<create-default-dbms-tables>CreateOnly</create-default-dbms-tables>
database-type
Function
The database-type element specifies the database used as the underlying dbms.
Example
<database-type>POINTBASE</database-type>
data-source-name
Function
Specifies the JDBC data source name to be used for database connectivity for this bean. For more information on datasources, see Programming WebLogic JDBC.
Example
See table-name.
db-cascade-delete
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:
If db-cascade-delete is enabled in weblogic-cmp-rdbms-jar.xml, you must
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 for Cascade Delete
The following Oracle 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
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
Function
Specifies the type of the cmp-field. the current field to a Blob or Clob in an Oracle database or a LongString or SybaseBinary in a Sybase database.
OracleBlob—maps the field to an Oracle Blob.OracleClob—maps the field to an Oracle Clob.LongString—tells the container to usesetCharacterStreamto write String data into the database. Some JDBC drivers have problems writing more than 4K of data usingsetString.SybaseBinary—tells the container to usesetBytesto write bytes into the binary column, becausesetBinaryStreamdoes not work withSybaseXADriver.
Example
<field-map>
<cmp-field>photo</cmp-field>
<dbms-column>PICTURE</dbms-column>
<dbms_column-type>OracleBlob</dbms-column-type>
</field-map>
default-dbms-tables-ddl
Function
Specifies the DDL file name to which the EJB container writes the table creation scripts.
delay-database-insert-until
Function
Specifies when a new CMP bean is inserted into the database. The allowable values cause the following behavior:
ejbCreate- perform database insert immediately afterejbCreate.This setting yields better performance thanejbCreateby avoiding an unnecessary store operation.ejbPostCreate- perform insert immediately afterejbPostCreate.
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 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
Function
The description element provides text that describes the parent element.
Example
<dscription>Contains a description of parent element</description>
ejb-name
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.
enable-batch-operations
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.
Note: In WebLogic Server 8.1, this element replaces the functionality of the commit setting, available in WebLogic Server 7.0, for the delay-database-insert-until element.
Example
The following XML sample demonstrates use of the enable-batch-operations element:
<enable-batch-operations>True</enable-batch-operations>
field-group
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 XML stanza 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
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 XML stanza 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>
foreign-key-column
Function
The foreign-key-column element represents a column of a foreign key in the database.
Example
See column-map.
foreign-key-table
Function
The foreign-key-table element specifies the name of a DBMS table that contains a foreign key.
Example
generator-name
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 SEQUENCE name by appending "_WL" to thegenerator-nameas part of the container's automatic SEQUENCE generation feature. For more information on automatic Oracle SEQUENCE generation, see Support for Oracle SEQUENCE.
- If the
generator-typeelement isOracle, and WebLogic Server is running in production mode, then the EJB container sets the name of the Oracle SEQUENCE to the value ofgenerator-name. - If the
generator-typeelement isNamedSequenceTable, then thegenerator-nameelement would be the name of theSEQUENCE_TABLEto be used.
Example
generator-type
Function
The generator-type element specifies the primary key generation method to use.
In addition, generator-type is used in conjunction with automatic Oracle SEQUENCE generation. See Support for Oracle SEQUENCE.
Example
group-name
Function
Specifies the name of a field group.
Example
See field-group.
include-updates
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>
<weblogic-ql>WHERE BALANCE>10000 ORDERBY NAME</weblogic-ql>
<include-updates>True</include-updates>
</weblogic-query>
instance-lock-order
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.instance-lock-order—ValueOrder-Beans are processed in order based on the value of their primary key.ValueOrdershould 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
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 SEQUENCE when automatic SEQUENCE generation is enabled. See Support for Oracle SEQUENCE.
If generator-type is
Oracle—key-cache-sizemust match the Oracle SEQUENCE INCREMENT value. If there is a mismatch between this value and the Oracle SEQUENCE INCREMENT value, then there will likely be duplicate key problems.NamedSequenceTable—key-cache-sizespecifies how many keys the container will fetch in a single DBMS call- SQLServer—
key-cache-sizeis ignored.
Example
key-column
Function
The key-column element represents a column of a primary key in the database.
Example
See column-map.
lock-order
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 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.This flag is only used for cascade delete currently.
Example
The XML stanza can contain the elements shown here:
<lock-order>1</lock-order>
<!ELEMENT lock-order (PCDATA)>
max-elements
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
The XML stanza can contain the elements shown here:
<max-elements>100</max-elements>
<!ELEMENT max-element (PCDATA)>
method-name
Function
The method-name element specifies the name of a finder or ejbSelect method.
Note: The `*' character may not be used as a wildcard.
Example
See weblogic-query.
method-param
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
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
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
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 enable-batch-operations and delay-database-insert-until.
Example
The following sample XML demonstrates the use of the order-database-operations element.
<order-database-operations>True</order-database-operations>
primary-key-table
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.
Example
For examples, see relationship-role-map and Mapping a Bean on Primary Key Side of a Relationship to Multiple Tables.
query-method
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
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
The XML stanza can contain the elements 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
Function
The relation-caching element specifies relationship caching. For more information about relationship caching, see Relationship Caching.
Example
The XML stanza 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
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_BeanTable_1with primary key columnsPk_table1_pkColumn_1andPk_table1_pkColumn_2andPk_BeanTable_2with primary key columnsPk_table2_pkColumn_1andPk_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
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
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 OracleBlob 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 an OracleBlob. 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>
sql-select-distinct
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 caused 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>
table-map
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 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 XML stanza can contain the elements shown here:
<table-map>
<table-nme>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>
</table-map>
table-name
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-name>examples-dataSource-demoPool</data-source-name>
<table-name>ejbAccounts</table-name>
</weblogic-rdbms-bean>
</weblogic-rdbms-jar>
use-select-for-update
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.
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
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
The XML stanza can contain the elements shown here:
<validate-db-schema-with>TableQuery</validate-db-schema-with>
verify-columns
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
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 ANSIREAD_COMMITTEDandREPEATABLE_READlevels 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 ofReadresults in additional overhead since it generally increases the amount of optimistic checking the EJB container must perform. With theReadoption, 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 ofSERIALIZABLEconsistency.
Note: If verify-rows is set to Read then the verify-columns element may not 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>
weblogic-ql
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
Function
The weblogic-query element allows you to associate WebLogic specific attributes with a query, as necessary. For example, weblogic-query can be used to specify a query that contains a WebLogic specific extension to EJB-QL. Queries that do not take advantage of WebLogic extensions to EJB-QL should be specified in the ejb-jar.xml deployment descriptor.
Also, the weblogic-query element is 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 XML stanza 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>
<weblogic-ql>WHERE BALANCE>10000 ORDERBY NAME
</weblogic-ql>
<group-name>...</group-name>
<caching-name>...</caching-name>
<max-elements>...</max-elements>
<include-updates>...</include-updates>
<sql-select-distinct>...</sql-select-distinct>
</weblogic-query>
weblogic-rdbms-bean
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-name
table-map
field-group
relationship-caching
weblogic-query
dalay-database-insert-until
automatic-key-generation
check-exists-on-method
weblogic-rdbms-jar
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
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 he 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 sections that following for examples of how one-to-one, one-to-many, and many-to-many relationships are configured.
Defining a One-to-One Relationship
Listing 8-3 shows the weblogic-rdbms-bean stanza that defines a one-to-one relationship between the entities defined in Listing 8-1 and Listing 8-2. The weblogic-rdbms-relation stanza is in the weblogic-cmp-jar.xml file, after the weblogic-rdbms-bean stanzas.
<weblogic-rdbms-bean> <ejb-name>CountryEJB</ejb-name> <data-source-name>wlsd21-datasource</data-source-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>
<weblogic-rdbms-bean><ejb-name>CapitalEJB</ejb-name><data-source-name>wlsd21-datasource</data-source-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>
Listing 8-3 <weblogic-rdbms-relation> Stanza 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: CAPITAL_NAME is the column name for the foreign key in the Country table.
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> stanza in ejb-jar.xml.
Defining a One-to-Many Relationship
Listing 8-4 contains a sample <weblogic-rdbms-relation> stanza that defines a one-to-many relationship:
Listing 8-4 <weblogic-rdbms-relation> Stanza 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>
</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> stanza 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.
Listing 8-5 <weblogic-rdbms-relation> Stanza 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 8-4, 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
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-mapsub-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-namecan 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 cmrgetXXXmethod. - The
db-cascade-deletetag 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>
