Chapter 2. Developing a Simple Example
Now that you understand Message-Oriented Middleware and some JMS concepts, you are ready to write your first JMS application. This chapter provides a gentle introduction to JMS using the publish-and-subscribe messaging model. You will get your feet wet with JMS and learn some of the basic classes and interfaces. Chapter 4, covers publish-and-subscribe in detail, and Chapter 5, covers the point-to-point message model.
As with all examples in this book, example code and instructions specific to several vendors is provided in the book download at O'Reilly's web site (see the preface for details). You will need to install and configure your JMS provider according to the instructions provided by your vendor.
The Chat Application
Internet chat provides an interesting application for learning about the JMS pub/sub messaging model. Used mostly for entertainment, web-based chat applications can be found on thousands of web sites. In a chat application, people join virtual chat rooms where they can "chat" with a group of other people.
To illustrate how JMS works, we will use the JMS pub/sub API to build a simple chat application. The requirements of Internet chat map neatly onto the publish-and-subscribe messaging model. In this model, a producer can send a message to many consumers by delivering the message to a single topic. A message producer is also called a publisher and a message consumer is also called a subscriber . In reality, using JMS for a ...