Introduction

Service-oriented architecture

Service-oriented architecture (SOA) is an architectural approach that supports the flexible integration of IT systems. It does this by providing a method to disconnect the service provider (service capability which delivers a defined action) from the service requester (client that sends the request). This enables the substitution of one service provider for another, without the requester being aware of the change and without the need to alter the architecture as shown in Figure 1.

By adopting an SOA approach and implementing it using supporting technologies, companies can build flexible systems that implement changing business processes quickly, and make extensive use of reusable components.

Services are the building blocks of SOA, providing function as a base point for building distributed systems. Services can be invoked independently by either external or internal service consumers to process single functions, or can be linked together to form more complex functionality and so quickly devise new functionality.

The Enterprise Service Bus

An ESB is used to connect a service requester to a service provider so that messages can be routed between the two platforms. The ESB is a collection of software components that manage messaging from one part of the network to another. The ESB handles mismatches between the requesters and providers, including protocol, interface or quality of service mismatches.

The ESB processes messages exchanged between the service endpoints. A service endpoint is a location where the service is available on the network. In contrast with regular business application components, the ESB is concerned with the flow of the messages through the infrastructure and not just with the business content of the messages. Rather than performing business functions, the ESB performs mediation capabilities including routing, transformation, and logging operations on the messages.