WebSphere Application Server - Express, Version 6.0.x     Operating Systems: AIX, HP-UX, Linux, Solaris, Windows

EJB containers

An Enterprise JavaBeans (EJB) container provides a run-time environment for enterprise beans within the application server. The container handles all aspects of an enterprise bean's operation within the application server and acts as an intermediary between the user-written business logic within the bean and the rest of the application server environment.

One or more EJB modules, each containing one or more enterprise beans, can be installed in a single container.

The EJB container provides many services to the enterprise bean, including the following:

By dynamically maintaining a set of active bean instances and synchronizing bean state with persistent storage when beans are moved into and out of active state, the container makes it possible for an application to manage many more bean instances than could otherwise simultaneously be held in the application server's memory. In this respect, an EJB container provides services similar to virtual memory within an operating system.

Between transactions, the state of an entity bean can be cached. The EJB container supports option A, B, and C caching.

By default, an EJB container runs in the quick start mode. The EJB container startup logic delays the loading and processing of all EJB types except Message Driven Beans (because they must exist before messages are posted for them), Startup Beans (which must be processed at server startup time), and those EJB types that you specify to initialize at server start. For more information about disabling quick start for EJB types, see Changing enterprise bean types to initialize at application start time using the Application Server Toolkit.

All other EJB initialization is delayed until the first use of the EJB type. When using Local Interfaces, the first use is when you perform an InitialContext.lookup() method for the type. For Remote Interfaces, it is when you call the first method on an EJB or its Home.

For more information about EJB containers, see "Resources for learning."




Related concepts
Enterprise beans

Related tasks
Managing EJB containers

Related reference
Enterprise beans: Resources for learning

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Last updated: Jun 8, 2005 12:45:23 PM EDT
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