Foreword

Building distributed yet integrated systems remains a difficult problem to solve. First, it requires a solid understanding of the individual components to be connected. Next, we have to connect these components in a way that balances loose coupling against system-wide requirements, such as latency and security. Last but not least, the resulting system has to be monitored and managed. Over time, a number of approaches have set out to solve these challenges: distributed components, EAI messaging, and, more recently, service-oriented architectures (SOA). While these approaches and tools have been a tremendous help, there is still no easy step-by-step recipe for balancing potentially opposing requirements into a coherent solution.

This is why design patterns are such a critical resource for building successful SOA solutions. Patterns encode knowledge and experience in a way that can be applied in a variety of contexts and technologies. They are not a one-size-fits-all silver bullet, but they do present forces and counterforces that steer us toward a reusable, well-balanced solution. At the same time, they form an important vocabulary that allows us to communicate our design decisions succinctly and precisely.