Jos Dirksen - SOA Governance in Action: REST and WS-* Architectures

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To my wife Brigitte, my daughter Sophie, and my parents

A few years ago, I wrote a book with a colleague about open source ESBs (Enterprise Service Buses), Open Source ESBs in Action (Manning, 2008). In that book we wrote about using open source tools to integrate applications and expose legacy systems as services. In the years that followed, ESBs were seen as one of the cornerstones of developing Service Oriented Architectures (SOAs). In 2008, when people talked about SOA, especially in the enterprise world, they meant the traditional SOAP-over-HTTP-based services. Everyone was doing this, the big vendors promoted it, and it finally looked like we had a way to create services that could be used by other departments and multiple users.

Over the next couple of years I wrote many services myself and was part of many projects that tried to use SOA concepts to create reusable services. What I noticed was that every company and every department had their own standards, tools, technologies, and a set of principles they used to determine how a service should be written. For one project we created a RESTful service using Scala without writing any documentation; for another project, we meticulously documented each element and operation of a SOAP/HTTP-based service. But the goals for both projects were the same: we wanted to create a service that would have a long life, would be used by many consumers, and was easy to maintain and possibly extend.

One thing I know is that developers and architects want to create good services, but what is almost always missing is a solid set of rules and standards to follow when developing a service. In our projects we often create a set of coding standards that are enforced through an IDE plugin, as well as some coding guidelines and dos and donts. While that assures the quality of the code, it isnt enough to create an easy-to-use service. For this you also need a set of rules, a set of principles that determines how your client interacts with your service. In other words, it is good to have a set of policies that help you define the contract of your service.

And what happens after a service is in production? I know from experience that measuring who is using a service and garnering insight into the business processes using your service can give you valuable information. This information can help you determine where to focus your development, where to add resources, and much more.

What I needed was a form of SOA governance. I wanted a set of policies we could use while creating the service (design-time governance) and a way to measure how our services were being used (runtime governance). Most books on SOA governance focus on the process, which is also very important, but they often lack practical examples. This book tries to provide you both with a set of guidelines for and practical examples of how to apply SOA governance.

I hope this book will show you that getting started with SOA governance isnt that hard and that it provides many advantagesand that there are plenty of open source tools that can help you take the first steps.

Writing a book is a long and difficult effort. I couldnt have done this without the support and hard work of many others. There are many people Id like to thank:

• Michael Stephens at Manning who helped me with the initial proposal. Without his help this book wouldnt have seen the light of day.
• My technical proofreader, Niek Palm, who worked tirelessly during the holiday period to meticulously work through the examples and the content. I appreciate that he always spoke his mind, and didnt always agree with me or with what Id written.
• My copyeditor Linda Rechtenwald for her hard work translating my non-native written English to readable text. You wouldnt believe how many times she corrected my errors.
• Katie Tennant and Melody Dolab for proofreading the book and making my work easier by ensuring that everything was consistent.
• All the other people at Manning who helped me get this book published. Thanks for believing in this book and helping me all along the way.
• Id also like to thank my development editors who guided me through the many stages of the book: Scott Meyers, Jeff Bleiel, and Dean DeChambeau.
• Thanks to the following reviewers who read the manuscript at various stages of development. Your valuable and sometimes critical comments made this a better book: Alberto Lagna, Andy Verberne, Barry Polley, David Dossot, Hemant Bedekar, Jason Coates, Javier Carro, Jeroen Benckhuijsen, Padmavathy Ramesh, Roy Prins, Sander Rossel, Senaka L. Fernando, Tijs Rademakers, and Tray Scates.
• Thanks to the guys at WSO2 for creating such great 100% open source products.
• Special thanks to Edwin Damen and Jac Speelman at JPoint (my employer), for giving me the time to finish the last couple of chapters, instead of sending me out to clients.
• A final thank-you to my wife who, once again, had to endure many long days and evenings without me while I sat at my laptop. And I couldnt have done this without my daughter who always succeeds in cheering me up when Im down.

Welcome to SOA Governance in Action. The main goal of this book is to introduce you to SOA governance and provide you with a set of guidelines and policies you can use to get started introducing SOA governance to your organization.

The book is divided into three parts. In the first part youll be introduced to the theory behind SOA governance and youll set up an environment that you can experiment with. In the second and third parts of the book, we look at and discuss various concepts you can use to start governing your SOA.