Apache activemq is a message broker built around java message service (jms) api : allow sending messages between two or more clients in a loosely coupled, reliable, and asynchronous way.

"protocol buffers" are language-neutral, platform-neutral, extensible way of serializing structured data for use in communications protocols or data storage.

this package, used by apache activemq, provide a simple protocol buffer java api. it comes with a built in proto file compiler and java source code generator (as a maven plugin).