Foreword

Enterprise service bus is a loosely defined term, and lots of products are claiming to implement the ESB concept. This concept is covered in depth in the first chapter of this book; in short, the goal is to provide a distributed and reliable mediation framework that the different systems in an IT environment can use to communicate, thus removing the need for a given system to know how to talk to the others in a specific way. Integration, which is what ESBs are about, is complicated: Each time you add a system, it needs to talk to all the other systems, and ad-hoc integration between the systems has long been considered a bad solution.

The concept of EAI emerged as a solution, but it led to another set of problems related to using a hub-and-spoke architecture, where a single system, the EAI broker, becomes the center of the system and a single point of failure. The next step of this evolution led to what is now known as an ESB: Data and exchanges are conveyed from system to system in a single logical bus, decoupling all the systems from each other. This leads to a much more maintainable system and can save a lot of time in the long term.