The latest version of CQRS framework Axon supports annotations and ordering of event handlers together with performance improvements. The recently released version 2.1 also adds compatibility with OSGi. Improvements in this new version includes:
- Publisher Acknowledgements as an alternative to transactions for increased speed when using the AMQP connector, implemented e.g. by RabbitMQ.
- A more efficient conflict resolution for an aggregate by only loading events describing the conflict and needed for the resolution instead of loading a new instance of the aggregate.
- New annotations for event handlers to make a clear separation from event listeners.
- With several handlers for a specific event, the order of invocation of each handler can be specified.
- Meta data may be attached to an event also during a unit of work, e.g. just before an event is stored and published.
- When events are replayed a filter can now be applied to remove events not of interest, thus increasing speed by only replaying part of the history.
- Post-processing on asynchronous event handlers for performing actions after an event is processed.
- All components delivered by Axon are now compatible with OSGi. Currently no optimizations are provided, but the intention is to include concrete optimizations for OSGi environments in future versions.
The revised documentation includes a QuickStart Guide with the steps needed to build a simple system based on Axon.
Axon Framework provides the building blocks for systems based on the CQRS and Event Sourcing architectural patterns. The framework was founded by Allard Buijze as an open source product, licensed under the Apache License, Version 2.0, with commercial support as an option.
A forum for Axon users is available with about 250 members and so far around 450 topics. An ongoing discussion about real life experiences reveals both positive and negative feedback.