The bus

At the core of JBoss ESB is the concept of a bus, an abstract representation of the transports through which request messages will be delivered to the target services and their response messages, if appropriate, returned to the service invoker. Each service 'plugs into the bus' by defining the configuration for its associated transports within the jboss-esb.xml file, the details of which will then be used to create and register Endpoint References (EPRs) within the Service Registry.

The ServiceInvoker, used by clients to invoke ESB services, will query the service registry to locate the EPRs associated with the service, choose one based on the current policy in force, and send the message through the transport associated with the chosen EPR.