Understanding the Messaging Framework

The advantage of networking your applications is that one application can send data to another application. However, many applications don't have the ability to read or process data coming from another application. Mule ESB solves this problem by providing a messaging framework that reads, transforms, and sends data as messages between applications. A message is simply a packet of data that can be handled and sent between applications on a specific channel (also called a queue).

At the simplest level, when you connect applications to Mule, it reads data from one application, transforms it as needed so it can be read by the target application, and sends it to that application. This allows you to integrate all types of applications, even those that were not built to be integrated.

Mule is a messaging framework based on ideas from Enterprise Service Bus (ESB) architectures. The key advantage of an ESB is that it allows different applications to communicate with each other by acting as a transit system for carrying data between applications within your intranet or across the Internet. The heart of the system is the message bus, which routes messages between applications.

One difference between Mule and a traditional ESB is that Mule only converts data as needed. With a typical ESB, you have to create an adapter for every application you connect to the bus and convert the application's data into a single common messaging format. The development of these adapters and the time required to process every message requires a lot of time and effort. Mule eliminates the need for a single message format. The information is sent on any communication channel, such as HTTP or JMS, and is translated only as needed along the way. Therefore, Mule increases performance and reduces development time over a traditional ESB.

The Mule architecture and terminology use the principles described in the book Enterprise Integration Patterns: Designing, Building, and Deploying Messaging Solutions by Gregor Hohpe and Bobby Woolf. This book is highly recommended reading for anyone involved in working with enterprise messaging solutions.

The next section, Understanding the Mule Architecture, describes the Mule architecture in greater detail.