Enterprise JavaBeans Technology

An Enterprise JavaBeans (EJB) component, or enterprise bean, is a body of code having fields and methods to implement modules of business logic. You can think of an enterprise bean as a building block that can be used alone or with other enterprise beans to execute business logic on the Java EE server.

Enterprise beans are either session beans or message-driven beans.

• A session bean represents a transient conversation with a client. When the client finishes executing, the session bean and its data are gone.

• A message-driven bean combines features of a session bean and a message listener, allowing a business component to receive messages asynchronously. Commonly, these are Java Message Service (JMS) messages.

In the Java EE 6 platform, new enterprise bean features include the following:

• The ability to package local enterprise beans in a WAR file

• Singleton session beans, which provide easy access to shared state

• A lightweight subset of Enterprise JavaBeans functionality (EJB Lite) that can be provided within Java EE Profiles, such as the Java EE Web Profile.

The Interceptors specification, which is part of the EJB 3.1 specification, makes more generally available the interceptor facility originally defined as part of the EJB 3.0 specification.