ChainBuilder ESB is Java Business Integration (JBI) compliant open source solution for use in Service Oriented Architecture (SOA) environments. ChainBuilder ESB's graphical integration enables new and older applications to easily enter into SOA.
Mule is the leading open source ESB (Enterprise Service Bus) and integration platform. It is a scalable, highly distributable object broker that can seamlessly handle interactions with services and applications using disparate transport and messaging technologies.
This is a simple example of how to use messaging, implemented in JMS [JMS]. It shows how to implement Request-Reply, where a requestor application sends a request, a replier application receives the request and returns a reply, and the requestor receives