RMI is an easy way to communicate between JVMs. It is particularly helpful for the encapsulation of e.g. legacy JNI code or any other unstable part of the system.
NEW 2016: Java EE 7 Workshops: Bootstrap, Effective, Architectures, April, 4th-6th, Munich's Airport
On demand workshops: Java EE 7 Bootstrap, Effective Java EE 7 and NEW: Java EE 7 Testing are available for streaming