EJB overview

EJB Overview

Session beans execute a particular business task on behalf of a single client during a single

session. Session beans can be stateful or stateless, but are not persistent; when a client finishes

with a session bean, the bean goes away.

Entity beans represent business objects in a data store, usually a relational database system.

Persistence—loading and saving data—can be bean-managed or container-managed. More than

just an in-memory representation of a data object, entity beans have methods that model the

behaviors of the business objects they represent. Entity beans can be accessed concurrently by

multiple clients and they are persistent by definition.

The container creates an instance of the message-driven bean or it assigns one from a pool to

process the message. When the message is received in the JMS Destination, the message-driven

bean assigns an instance of itself from a pool to process the message. Message-driven beans are

not associated with any client. They simply handle messages as they arrive.