After quite some time of trying-out and developing applications based on the CQRS architecture, I noticed that much of the code involved plumbing and no so much project specific code. I decided to make the architectural code available trough an open source project: cqrs4j

cqrs4j is a Spring-oriented framework that provides the most important building blocks of a CQRS architecture. Creating an aggregate becomes really simple. You don’t have to worry about managing the storage and dispatching of (uncommitted) events. Event sourcing becomes as easy as wiring two beans in your application context.

Annotation support

cqrs4j comes with out-of-the-box annotation support. This makes is really easy to wire event handler methods. cqrs4j can automatically subscribe all your event handlers to the event bus and delegate all relevant events to the appropriate event handlers. Enabling annotation support is as easy as wiring a single bean in your application context.

Spring Integration support

Spring Integration is a framework that allows easy developments of a Messaging systems using the pipes-and-filters architecture. This fits nicely with most of the event dispatching process of CQRS. cqrs4j has support for Spring Integration, which allows you to publish all events as messages on a Spring Integration channel. Sending messages through JMS queues, via email, or through file system storage will only take a few lines of (XML) configuration.

Transaction support

If you update your database tables through incoming events, dealing with them one-by-one in a transaction can become time consuming and take up too much resources of your database. With cqrs4j, you can configure transactions just by setting the @Transactional annotation on your event handlers. You can also configure how many events should be handled in a single transaction.

cqrs4j is an open source project, licensed under the Apache 2 license. Visit the project home page for the latest downloads, documentation and source code at code.google.com/p/cqrs4j.

CQRS presentation in March

On our March 9th meetup, Erik Roosendaal will be presenting about the CQRS architecture. Keep an eye on the agenda for more information.