The core of any Enterprise Service Bus (ESB) revolves around the definition of services and the way in which these services communicate with each other. How you choose to break up your application into services, whether dealing with the integration of legacy components or designing new functionality, and how they communicate can have a large effect on the performance, flexibility and resilience of your application.
It is important to spend time thinking about these issues. Get it right and you will end up with a loosely coupled system that reuses functionality rather than reimplements it. In order to make effective architectural decisions it is first necessary to understand the concepts behind the JBoss ESB Service, including their communication "on the bus", so that these can best be applied to your application.
In this chapter we will cover JBoss ESB Services, explaining the structure of the ESB message, the mechanics behind the Action Pipeline and the choices you have for implementing actions.
You will learn about:
- The structure of ESB messages and how to validate them
- The configuration mechanism within JBoss ESB
- The service pipeline and service actions
- Service chaining and continuations
- Transactional behavior and its effect on the pipeline
- Security context and its propagation
So let's get on with it...
The examples in this chapter are based on a standard ESB application template that can be found under the Chapter3 directory within the sample downloads. We will modify this template application as we proceed through this chapter.
Before we start, please make sure that you have set up JBoss Developer Studio and the JBoss 5.1 Runtime as described in Chapter 2.