To this day, enterprise message queuing is a concept that is not well understood by most software developers. Commercial message-oriented middleware (MOM) did not help to encourage adoption of the process; most of the MOMs on the market were closed source, were costly to buy and support, and required trained system administrators for proper installation. ActiveMQ was developed to provide an open source alternative: its central theme is to put the power in the hands of developers. To date, the ActiveMQ project has been successful in this endeavor by creating a MOM that is easy to install, administer, and utilize, while providing a large number of unique features.

Today, six or seven years after ActiveMQ was originally created, it’s surprising how far and widely it is being used. ActiveMQ is a crucial component in many applications. Used by small businesses and very large enterprises alike, ActiveMQ is deployed throughout a wide variety of industries around the world including manufacturing, government, retail, healthcare, finance, military, telecom, and many more. The versatility of not only ActiveMQ but also event-based systems has appealed to a very large audience of users and that appeal continues to grow.

In writing a book about ActiveMQ, our intent was to provide a comprehensive guide for its features and how to use them. Although ActiveMQ implements the JMS specification, which has not moved in many years, ActiveMQ provides many features beyond this spec and it has not stopped innovating. As is always the case, authoring a book about software is a game of chase; as the software evolves, so must the book that is still being written. We did our best to keep this book up to date with ActiveMQ 5.4.1.

We hope that, by reading this book, you will come to appreciate not only ActiveMQ but the concepts surrounding event-based systems. After all, some of the largest systems in the world are designed using events and message queuing.