Day 13. Understanding JMS and Message-Driven Beans

Today we'll explore the Java Message Service (JMS) and give a brief account of message-driven beans. JMS is the standard API used by J2EE applications to access Message-Oriented Middleware (MOM) services. Messaging is the ability of applications to interact and communicate with each other asynchronously. This is different from e-mail messaging, which takes place between humans. Message-driven applications are designed to accomplish loose coupling and portability. Each part of these enterprise applications can be developed as self-contained business components, and then can be integrated into a reliable yet flexible system. In general, messaging plays an important role in any large enterprise, and is usually a major part in integrating legacy systems with B2B and B2C applications.

Today's road map is to learn the main concepts and models of JMS, and to give an overview of message-driven beans, in particular:

• Learn about JMS architecture and its main objectives

• Study the API of both messaging models: point-to-point and publish/subscribe, and know when to use them

• Learn how to write a JMS client—either a message consumer or a message producer—in both messaging models

• Scratch the surface of message-driven beans, and learn how to use them as JMS consumers