EJB.6.1 Overview

A session bean instance is an instance of the session bean class. It holds the session object's state.

By definition, a session bean instance is an extension of the client that creates it:

• Its fields contain a conversational state on behalf of the session object's client. This state describes the conversation represented by a specific client/session object pair.

• It typically reads and updates data in a database on behalf of the client. Within a transaction, some of this data may be cached in the instance.

• Its lifetime is controlled by the client.

  A container may also terminate a session bean instance's life after a deployer-specified timeout or as a result of the failure of the server on which the bean instance is running. For this reason, a client should be prepared to recreate a new session object if it loses the one it is using.

Typically, a session object's conversational state is not written to the database. A session bean developer simply stores it in the session bean instance's fields and assumes its value is retained for the lifetime of the instance.

On the other hand, the session bean must explicitly manage cached database data. A session bean instance must write any cached database updates prior to a transaction completion, and it must refresh its copy of any potentially stale database data at the beginning of the next transaction.