J2EE™ and Beyond: Design, Develop, and Deploy World-Class Java™ Software

Introduction

As we saw in the previous chapter, messaging provides one facility for loosely coupled communication between components. With messaging, components don't communicate directly via method calls (as they do with EJBs); instead they communicate using a message, usually one with a predefined format that allows it to be parsed and processed by listeners.

Another facility often used for simple messaging is email. Though email servers often lack many of the controls of messaging servers (delivery acknowledgment, transactions), they do provide a low cost, easy to implement solution for applications which do not require these controls. Email could be used to send and receive formatted messages or for providing automated communication between ...