Java Message Service, 2nd Edition

Chapter 5. Publish-and-Subscribe Messaging

This chapter focuses on the publish-and-subscribe (pub/sub) messaging model. This messaging model is used when you need to broadcast an event or message to many message consumers. Unlike the point-to-point messaging model discussed in Chapter 4, all message consumers (called subscribers) listening on the topic will receive the message.

In this chapter, we will describe the publish-and-subscribe model through the use of a typical broadcast messaging scenario where a mortgage lender publishes its latest mortgage rates for a 30-year fixed mortgage to various borrowers in the hope of attracting one of the borrowers to apply for a mortgage loan. The TLender class will publish a new mortgage rate through a topic, and the TBorrower class will subscribe to the topic and make a decision on whether or not it is a good rate.

We have mentioned several new terms already in this chapter: topic, subscriber, and publish. Before moving on to the code example, we will first describe the main characteristics and nomenclature of the publish-and-subscribe model and discuss some of the typical use cases for this model.

Publish-and-Subscribe Overview

The publish-and-subscribe model is more commonly referred to as the pub/sub model. In this model, the message producer is called a publisher and the message consumer a subscriber. Messages are published to a topic as opposed to being sent to a queue, as in the point-to-point model. The most important characteristics ...