About the Session Bean Containers

Like an entity bean, a session bean can access a database through Java^TM Database Connectivity (JDBC^TM) calls. A session bean can also provide transaction settings. These transaction settings and JDBC calls are referenced by the session bean’s container, allowing it to participate in transactions managed by the container.

A container managing stateless session beans has a different charter from a container managing stateful session beans.

Stateless Container

The stateless container manages stateless session beans, which, by definition, do not carry client-specific states. All session beans (of a particular type) are considered equal.

A stateless session bean container uses a bean pool to service requests. The Application Server specific deployment descriptor file, sun-ejb-jar.xml, contains the properties that define the pool:

• steady-pool-size

• resize-quantity

• max-pool-size

• pool-idle-timeout-in-seconds

For more information about sun-ejb-jar.xml, see The sun-ejb-jar.xml File.

The Application Server provides the wscompile and wsdeploy tools to help you implement a web service endpoint as a stateless session bean. For more information about these tools, see the Sun Java System Application Server Enterprise Edition 8.2 Reference Manual.

Stateful Container

The stateful container manages the stateful session beans, which, by definition, carry the client-specific state. There is a one-to-one relationship between the client and the stateful session beans. At creation, each stateful session bean (SFSB) is given a unique session ID that is used to access the session bean so that an instance of a stateful session bean is accessed by a single client only.

Stateful session beans are managed using cache. The size and behavior of stateful session beans cache are controlled by specifying the following sun-ejb-jar.xml parameters:

• max-cache-size

• resize-quantity

• cache-idle-timeout-in-seconds

• removal-timeout-in-seconds

• victim-selection-policy

The max-cache-size element specifies the maximum number of session beans that are held in cache. If the cache overflows (when the number of beans exceeds max-cache-size), the container then passivates some beans or writes out the serialized state of the bean into a file. The directory in which the file is created is obtained from the EJB container using the configuration APIs.

For more information about sun-ejb-jar.xml, see The sun-ejb-jar.xml File.

The passivated beans are stored on the file system. The Session Store Location setting in the EJB container allows the administrator to specify the directory where passivated beans are stored. By default, passivated stateful session beans are stored in application-specific subdirectories created under domain-dir/session-store.

Make sure the delete option is set in the server.policy file, or expired file-based sessions might not be deleted properly. For more information about server.policy, see The server.policy File.

The Session Store Location setting also determines where the session state is persisted if it is not highly available; see Choosing a Persistence Store.