An Introduction to Enterprise Service Bus

The first chapter of Open-Source ESBs in Action has a good introduction to Enterprise Service Bus. The followings are discussed in the chapter.

• EAI vs. ESB
1. EAI products are based on the hub and spoke model. All data exchange is centralized in the hub.
   
2. ESB products are based on the bus model. Data are distributed to the destinations through the bus. In the distribution process, data/messages can be transformed or enhanced.
   
3. The data exchange in ESB products is based on open standards, such as, JCA, XML, JMS, and web services standards.
   
• Reasons to start thinking of an ESB
1. Necessity to integrate applications
2. Heterogonous environment
3. Reduction of total cost of ownership
   
• Core functionalities of an ESB
1. Location transparency
2. Transport protocol conversion
3. Message transformation
4. Message routing
5. Message enhancement
6. Security
7. Monitoring and management
• Current open source ESB projects
1. Mule
   
2. Apache ServiceMix
3. Open ESB
4. Apache Synapse
5. JBoss ESB
6. Apache Tuscany
7. Fuse ESB
8. WSO2 ESB
   
9. PEtALS
10. OpenAdapter

The authors also mentioned that Service Component Architecture (SCA) seems to be the next big thing in the ESB market. SCA is a specification based on the principles of service-oriented architecture. Vendors are investigating the possibility of transforming their ESB products to conform with the specification.