What is an ESB and what is it good for?

Question

At a previous job, there was lots of talk about \"Enterprise Service Bus\" (ESB). I read parts of a conceptual book about it, but never really understood how you would impl

Answer 1

Disclaimer: I work for IBM and consult on WebSphere ESB, an IBM product designed to build ESBs with. The following are my opinions and don't necessarily reflect IBM's position.

An ESB is different things to different people, unfortunately.

To me, an ESB is a any technology that you can insert into an SOA (Service-Oriented Architecture), allowing you to connect disparate systems together. It often performs the functions of protocol transformation, message modification, routing, logging, acting as a security gateway, and so on. For example, you might use an ESB to expose a service previously only available as a Web Service as a JMS-based service as well.

In this respect, ESB implementations (or to be more precise, software sold to build ESBs with - such as that I consult on) are often technologically similar to what used to be known as a messaging or queueing broker, although the purpose is somewhat different, because (as the acronyms imply) it's oriented around services rather than moving messages from one place to another. How important the distinction is technologically is a matter of opinion.