Sams Teach Yourself J2EE™ in 21 Days

Day 10. Message-Driven Beans

So far, you have looked at two types of Enterprise Java Bean (EJB)—the Session bean and the Entity bean. Today you will consider the third and final EJB, the Message-driven bean. Topics that are covered are as follows:

• Similarities and differences with Entity and Session beans

• The life-cycle of a Message-driven bean

• Writing a Message-driven bean

Prior to the EJB 2.0 specification, it was only possible to support asynchronous message passing by writing an external Java program that acted as a listener. A listener is a program whose sole purpose is to wait for data to arrive, for example, a socket server program that “listens” on a socket and perform some action when it detects client connections. The listener was then ...