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J2EE™ Applications and BEA™ WebLogic Server™ by Sandra L. Emerson, Rob Woollen, Michael Girdley

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Basics of EJBs

In EJB 2.0, there are four types of EJBs:

  • Stateless session beans provide a service without storing a conversation state between method calls.

  • Stateful session beans maintain state; each instance is associated with a particular client.

  • Entity beans represent an object view of persistent data, usually rows in a database. Entity beans have a primary key as a unique identifier. There are two operational styles for entity beans: container-managed persistence (CMP) and bean-managed persistence (BMP).

  • Message-driven beans were added in EJB 2.0. Message-driven EJBs, the integration between JMS (Java Message Service) and EJB, are used to perform asynchronous work within the server.

Session Beans

Session beans (both stateful and stateless) ...

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