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Oracle® Application Server Containers for J2EE Enterprise JavaBeans Developer's Guide
10g Release 2 (10.1.2) Part No. B15505-01 |
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Oracle® Application Server Containers for J2EE Enterprise JavaBeans Developer's Guide
10g Release 2 (10.1.2) Part No. B15505-01 |
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Previous |
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The mapping of the assembly descriptor elements.
Enables the application deployer to control or restrict the usage of the asynchronous methods defined on the AC4J bean. You specify the user identity that is allowed to execute all methods of the bean in this element. The identities that can be execute the AC4J beans are identified in one or more <caller> elements.
Each caller identity allowed to execute methods on the AC4J bean are defined in a single <caller> element.
Attributes:
Deployment information for a container-managed persistence field. If no subtags are used to define different behavior, the field is persisted through serialization or native handling of "recognized" primitive types.
Attributes:
ejb-reference-home - The JNDI-location of the fields remote EJB-home if the field is an entity EJBObject or an EJBHome.
name - The name of the field.
persistence-name - The name of the field in the database table.
persistence-type - The database type (valid values varies from database to database) of the field.
Specifies a relational mapping of a Collection type. A Collection consists of n unordered items (order isnt specified and not relevant). The field containing the mapping must be of type java.util.Collection.
Attributes:
table - The name of the table in the database.
An attribute sent to the context. The only mandatory attribute in JNDI is the 'java.naming.factory.initial' which is the classname of the context factory implementation.
Attributes:
name - The name of the attribute.
value - The value of the attribute.
The name and url of a specific Databus for an AC4J object.
Attributes:
data-bus-name - The user-defined name of the Databus.
url - The URL of the Databus, which is similar to a JDBC URL.
The default method access policy for methods not tied to a method-permission.
A short description.
The ejb-name element specifies an enterprise bean's name. This name is assigned by the ejb-jar file producer to name the enterprise bean in the ejb-jar file's deployment descriptor. The name must be unique among the names of the enterprise beans in the same ejb-jar file. 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. The name must conform to the lexical rules for an NMTOKEN.
The ejb-ref element that is used for the declaration of a reference to another enterprise bean's home. The ejb-ref-mapping element ties this to a JNDI-location when deploying.
Attributes:
location - The JNDI location to look up the EJB home from.
name - The ejb-ref's name. Matches the name of an ejb-ref in ejb-jar.xml.
The beans contained in this EJB JAR file.
Deployment information for an entity bean.
Attributes:
call-timeout - The time (long milliseconds in decimal) to wait for any resource that the EJB uses, except database connections, if it is busy (before throwing a RemoteException, treating it as a deadlock). This is also used as a SQL query timeout. If the timeout occurs before the SQL query finishes, a SQL exception is thrown. If zero, the timeout is disabled. The default is 90 seconds.
copy-by-value - Whether or not to copy all the incoming/outgoing parameters for all incoming and outgoing EJB calls. Set to 'false' if your application does not assume copy-by-value semantics for these parameters. The default is 'true'.
data-source - The name of the data source used if using container-managed persistence.
delay-updates-until-commit - Defers the flushing of transactional data until commit time or not. The default is true. If you want each change to be updated in the database, set this element to false.
do-select-before insert - If false, you avoid executing a select before an insert. The extra select normally checks to see if the entity already exists before doing the insert to avoid duplicates.
If a unique key constraint is defined for the entity, then we recommend setting this to false. If there is no unique key constraint, setting this to false leads to not detecting a duplicate insert. To prevent duplicate inserts in this case, leave it set to true.
For performance, Oracle recommends setting this to false to avoid the extra select before insert. Default Value: true
exclusive-write-access - Whether or not the EJB-server has exclusive write (update) access to the database backend. This can be used only for entity beans that use a "read_only" locking mode. In this case, it increases the performance for common bean operations and enables better caching. The default is false. See "Specifying Exclusive Write Access to the Database" for more information.
findByPrimaryKey-lazy-loading="true|false" - For entity bean finder methods, lazy loading can cause the select method to be invoked more than once. To turn on lazy loading and enforce only a single execution of this finder method, set this property to true. The default is false. See "Configuring Lazy Loading on CMP Entity Bean Finder Methods" for more information.
instance-cache-timeout - The amount of time in seconds that entity wrapper instances are assigned to an identity. If you specify 'never', you retain the wrapper instances until they are garbage collected. The default is 60 seconds.
isolation - Specifies the isolation-level for database actions. The valid values for Oracle databases are 'serializable' and 'committed'. The default is 'committed'. Non-Oracle databases can be the following: 'none', 'committed', 'serializable', 'uncommitted', and 'repeatable_read'. For more information, see "Using Database Isolation Modes to Protect Against Resource Contention" and "Configuring Entity Bean Concurrency Modes For Handling Resource Contention" and Oracle Application Server Performance Guide .
local-wrapper - Name of the OC4J local home wrapper class for this bean. This is an internal server value and should not be edited.
locking-mode - The concurrency modes configure when to block to manage resource contention or when to execute in parallel. For more information, see "Using Database Isolation Modes to Protect Against Resource Contention" and "Configuring Entity Bean Concurrency Modes For Handling Resource Contention" and Oracle Application Server Performance Guide . The concurrency modes are as follows:
PESSIMISTIC: This manages resource contention and does not allow parallel execution. Only one user at a time is allowed to execute the entity bean at a single time.
OPTIMISTIC: Multiple users can execute the entity bean in parallel. It does not monitor resource contention; thus, the burden of the data consistency is placed on the database isolation modes. This is the default.
READ-ONLY: Multiple users can execute the entity bean in parallel. The container does not allow any updates to the bean's state.
max-instances - The number of maximum bean implementation instances to be kept instantiated or pooled. The default is 0, which means infinite. See "Configuring Pool Sizes For Entity Beans" for more information.
min-instances - The number of minimum bean implementation instances to be kept instantiated or pooled. The default is 0. See "Configuring Pool Sizes For Entity Beans" for more information.
max-tx-retries—The number of times to retry a transaction that was rolled back due to system-level failures. The default is 0. Leave the setting to zero if using the serializable isolation level. Within a transaction, the container uses the max-tx-retries value of the first invoked bean within the transaction. The performance guide recommends that you leave this value at 0 and add retries only where errors are seen that could be resolved through a retry.
tx-retry-wait—This parameter specifies the time to wait in seconds between retrying the transaction. The default is 60 seconds.
name - The name of the bean, this matches the name of a bean in the assembly descriptor (ejb-jar.xml).
pool-cache-timeout - The amount of time in seconds that the bean implementation instances are to be kept in the "pooled" (unassigned) state, specifying 'never' retains the instances until they are garbage collected. The default is 60.
table - The name of the table in the database if using container-managed persistence.
validity-timeout - The maximum amount of time (in milliseconds) that an entity is valid in the cache (before being reloaded). Useful for loosely coupled environments where rare updates from legacy systems occur. This attribute is only valid for entity beans with locking mode of read_only and when exclusive-write-access="true" (the default).
We recommend that if the data is never being modified externally (and therefore you've set exclusive-write-access=true), that you can set this to 0 or -1, to disable this option, since the data in the cache will always be valid for read-only EJBs that are never modified externally.
If the EJB is generally not modified externally, so you're using exclusive-write-access=true, yet occasionally the table is updated so you need to update the cache occasionally, then set this to a value corresponding to the interval you think the data may be changing externally.
update-changed-fields-only - Specifies whether the container updates only modified fields or all fields to persistence storage for CMP entity beans when ejbStore is invoked. The default is true, which specifies to only update modified fields. See "Create Data Consistency in Your Entity Bean by Using Persistence" for more information.
wrapper - Name of the OC4J remote home wrapper class for this bean. (internal server attribute, do not edit)
Specified the configuration for persisting an entity reference via it's primary key. The child-tag of this tag is the specification of how to persist the primary key.
Attributes:
home - JNDI location of the EJBHome to get lookup the beans at.
Overrides the value of an env-entry in the assembly descriptor. It is used to keep the EAR clean from deployment-specific values. The body is the value.
Attribute:
name - The name of the context parameter.
Specifies the configuration of a field-based (java class field) mapping persistence for this field. The fields that are to be persisted have to be public, non-static, non-final and the type of the containing object has to have an empty constructor.
The definition of a container-managed finder method. This defines the selection criteria in a findByXXX() method in the bean's home.
Attributes:
partial - Whether or not the specified query is a partial one. A partial query is the 'where' clause or the 'order' (if it starts with order) clause of the SQL query. Queries are partial by default. If partial="false" is specified then the full query is to be entered as value for the query attribute and you need to make sure that the query produces a result-set containing all of the CMP fields. This is useful when doing advances queries involving table joins and similar.
query - The query part of an SQL statement. This is the section following the WHERE keyword in the statement. Special tokens are $number which denotes an method argument number and $name which denotes a cmp-field name. For instance the query for "findByAge(int age)" would be (assuming the cmp-field is named 'age'): "$1 = $age".
lazy-loading - For entity bean finder methods, lazy loading can cause the select method to be invoked more than once. To turn on lazy loading and enforce only a single execution of this finder method, set this property to true. The default is false. See "Configuring Lazy Loading on CMP Entity Bean Finder Methods" for more information.
prefetch-size - Oracle JDBC drivers include extensions that allow you to set the number of rows to prefetch into the client while a result set is being populated during a query. This reduces round trips to the database by fetching multiple rows of data each time data is fetched—the extra data is stored in client-side buffers for later access by the client. The number of rows to prefetch can be set as desired. The default number of rows to prefetch to the client is 10. The number set here is passed along to the JDBC driver. See the Oracle 9i JDBC Developer's Guide and Reference for more information on using prefetch with a JDBC driver.
A group that this <security-role-mapping> implies. That is, all members of the specified group are included in this role.
Attributes:
name - The name of the group.
The <ior-security-config> element configures CSIv2 security policies for interoperability, which is discussed fully in the Interoperability chapter in the Oracle Application Server Containers for J2EE Services Guide.
Specifies an active EJB for deployment into the AC4J container.
Attributes:
Describes the database server where the Databus is installed
Attributes:
The specification of an optional javax.naming.Context implementation used for retrieving the resource. This is useful when using third party modules, such as a third party JMS server. Either use the context implementation supplied by the resource vendor or, if none exists, write an implementation that negotiates with the vendor software.
Attribute:
Specifies a mapping of the map key. Map keys are always immutable.
Attributes:
Deployment information for a MDB.
Attributes:
connection-factory-location: The JNDI location of the connection factory to use. The JMS Destination Connection Factory is specified in the connection-factory-location attribute. The syntax is "java:comp/resource" + resource provider name + "TopicConnectionFactories" or "QueueConnectionFactories" + user defined name. The xxxConnectionFactories details what type of factory is being defined.
destination-location: The JNDI location of the destination (queue/topic) to use. The JMS Destination is specified in the destination-location attribute. The syntax is "java:comp/resource" + resource provider name + "Topics" or "Queues" + Destination name. The Topic or Queue details what type of Destination is being defined. The Destination name is the actual queue or topic name defined in the database.
name - The name of the bean, this matches the name of a bean in the assembly descriptor (ejb-jar.xml).
subscription-name: If this is a topic, the subscription name is defined in the subscription-name attribute.
listener-threads: The listener threads are used to concurrently consume JMS messages. The default is one thread. Topics can only have one thread; queues can have more than one thread.
transaction-timeout: This attribute controls the transaction timeout interval (in seconds) for any container-managed transactional MDB. The default is one day or 86,400 seconds. If the transaction has not completed in this timeframe, the transaction is rolled back.
dequeue-retry-count—Specifies how often the listener thread tries to re-acquire the JMS session once database failover has incurred. This value is only for CMT transactions in an MDB. The default is "0." See "Failover Scenarios When Using a RAC Database" for more information.
dequeue-retry-interval—Specifies the interval between retries. The default is 60 seconds.
Specify the methods (and possibly parameters of that method) of the bean.
The method-intf element allows a method element to differentiate between the methods with the same name and signature that are defined in both the remote and home interfaces. The method-intf element must be one of the following: Home or Remote.
The method-name element contains a name of an enterprise bean method, or the asterisk (*) character. The asterisk is used when the element denotes all the methods of an enterprise bean's remote and home interfaces.
The method-param element contains the fully-qualified Java type name of a method parameter.
The method-params element contains a list of the fully-qualified Java type names of the method parameters.
An orion-ejb-jar.xml file contains the OC4J-specific deployment information for an EJB. It is used to specify initial deployment properties. After each deployment the deployment file is reformatted and altered by the server for additional information.
Attributes:
deployment-time - The time (long milliseconds in decimal) of the last deployment, if not matching the last editing date the jar will be redeployed. (internal server value, do not edit)
deployment-version - The version of OC4J this jar was deployed with, if it's not matching the current version then it will be redeployed. (internal server value, do not edit)
Designates how the primary key is mapped.
Specifies the configuration of a property-based (bean properties) mapping persistence for this field. The properties have to adhere to the usual JavaBeans specification and the type of the containing object has to have an empty constructor This is also designated within the EJB specification.
The resource-ref element is used for the declaration of a reference to an external resource such as a data source, JMS queue, or mail session. The resource-ref-mapping ties this to a JNDI-location when deploying.
Attributes:
The resource-env-ref-mapping element element is used to map an administered object for a resource. For example, to use JMS, the bean must obtain both a JMS factory object and a destination object. These objects are retrieved at the same time from JNDI. The <resource-ref> element declares the JMS factory and the <resource-env-ref> elment is used to declare the destination. Thus, the <resource-env-ref-mapping> element maps the destination object. See "Using a Logical Name When Client Accesses the MDB" for more information.
Attributes:
The security role that the AC4J EJB methods are run under when using the <run-as-specified-identity> element.
You can specify that all methods of an AC4J EJB execute under a specific identity. That is, the container does not check different roles for permission to run specific methods; instead, the container executes all of the AC4J EJB methods under the specified security identity.
Describes if the AC4J Databus should use the caller or run-as identity for the AC4J bean security.
The runtime mapping (to groups and users) of a role. Maps to a security-role of the same name in the assembly descriptor.
Attributes:
Deployment information for a session bean.
Attributes:
pool-cache-timeout—How long to keep stateless sessions cached in the pool. Only applies to stateless session beans. Legal values are positive integer values or 'never'. For stateless session beans, if you specify a pool-cache-timeout, then at every pool-cache-timeout interval, all beans in the pool, of the corresponding bean type, are removed. If the value specified is zero or negative, then the pool-cache-timeout is disabled and beans are not removed from the pool.
Default Value: 60 (seconds)
call-timeout—The time (long milliseconds in decimal) to wait for any resource that the EJB uses, excluding database connections, if it is busy. After this times out, a RemoteException is thrown and the EJB is treated as involved in a deadlock. If value is set to 0, OC4J waits for the EJB "forever". This is the default.
copy-by-value—Whether or not to copy (clone) all the incoming and outgoing parameters in EJB calls. Set to 'false' if you are certain that your application does not assume copy-by-value semantics for a speed-up. The default is 'true'.
local-wrapper—Name of the OC4J wrapper class for this bean. This is an internal server value and should not be edited.
location—The JNDI-name that this bean will be bound to.
max-instances - This attribute controls the number of bean instances allowed in memory—either instantiated or pooled. When this value is reached, the container attempts to passivate the oldest bean instance from memory. If unsuccessful, the container waits the number of milliseconds set in the call-timeout attribute to see if a bean instance is removed from memory, either through passivation, its remove() method, or bean expiration, before a TimeoutExpiredException is thrown back to the client. To allow an infinite number of bean instances, the max-instances attribute can be set to zero. Default is 0, which is infinite. This applies to both stateless and stateful session beans.
max-instances-threshold - This attribute defines a threshold for how many actives beans exist in relation to the max-instances attribute definition. Specify an integer that is translated as a percentage. If you define that the max-instances is 100 and the max-instances-threshold is 90%, then when the active bean instances reaches past 90, passivation of beans occurs. Default: 90%. To disable, specify "never".
max-tx-retries—The number of times to retry a transaction that was rolled back due to system-level failures. The default is 0. Within a transaction, the container uses the max-tx-retries value of the first invoked bean within the transaction. The performance guide recommends that you leave this value to 0 and add retries only where errors are seen that could be resolved through a retry.
tx-retry-wait—This parameter specifies the time to wait in seconds between retrying the transaction. The default is 60 seconds.
memory-threshold - This attribute defines a threshold for how much used JVM memory is allowed before passivation should occur. Specify an integer that is translated as a percentage. When reached, beans are passivated, even if their idle timeout has not expired. Default: 80%. To disable, specify "never."
min-instances - The number of minimum bean implementation instances to be kept instantiated or pooled. The default is zero. This applies only to stateless session beans.
name—The name of the bean, which matches the name of a bean in the assembly section of the EJB deployment descriptor (ejb-jar.xml).
resource-check-interval - The container checks all resources at this time interval. At this time, if any of the thresholds have been reached, passivation occurs. Default: 180 sec. (3 min.). To disable, specify "never."
passivate-count - This attribute is an integer that defines the number of beans to be passivated if any of the resource thresholds have been reached. Passivation of beans is performed using the least recently used algorithm. Default: one-third of the max-instances attribute. You can disable this attribute by setting the count to zero or a negative number.
persistence-filename—Path to the file where sessions are stored across restarts.
timeout—Inactivity timeout in seconds. If the value is zero or negative, then all timeouts are disabled. The default is 30 minutes. Every 30 seconds, the pool clean up logic is invoked. Within the pool clean up logic, only the sessions that timed out, by passing the timeout value, are deleted.
Adjust the timeout based on your applications use of stateful session beans. For example, if stateful session beans are not removed explicitly by your application, and the application creates many stateful session beans, then you may want to lower the timeout value.
If your application requires that a stateful session bean be available for longer than 30 minutes, then adjust the timeout value accordingly.
wrapper—Name of the OC4J wrapper class for this bean. This is an internal server value and should not be edited.
Specifies a relational mapping of a Set type. A Set consists of n unique unordered items (order is not specified and not relevant). The field containing the mapping must be of type java.util.Set.
Attributes:
table - The name of the table in the database.
You can specify that all methods of an AC4J EJB execute under the caller's identity.
A user that this security-role-mapping implies.
Attributes:
name - The name of the user.
Specified a mapping of the primary key part of a set of fields.
Attributes:
immutable - Whether or not the value can be trusted to be immutable once added to the Collection. Setting this to true will optimize database operations extensively. The default value is "true" for set-mapping and "false" for collection-mapping.
type - The fully qualified class name of the type of the value. Examples are com.acme.OrderEntry, java.lang.String, and so on.
