Appendix A. RMI and JNDI
Java Remote Method Invocation (RMI) and the Java Naming and Directory Interface (JNDI) are two central Java technologies that EJB 3 uses extensively under the hood. RMI is the technology that enables transparent Java native remote communication between EJB clients and beans. JNDI, on the other hand, enables a whole host of EJB functionality by acting as the central service registry for a Java EE container. One of the major enhancements in EJB 3, dependency injection (DI), is simply a wrapper over JNDI lookups.
In this appendix we offer a brief primer on both of these technologies, especially as they relate to EJB 3.
Java RMI made its debut very early in Java’s history. (also known Java Remote Method Protocol (JRMP)). It became clear that, as a platform that touts the distributed computing mantra “The network is the computer,” Java must provide a simple and robust mechanism for communication across JVM instances. Ideally, method calls on an object running in one JVM should be executed transparently in another remote JVM. With the help of a small amount of boilerplate setup code combined with a few code-generation tools, RMI delivers on this promise. To invoke an object method remotely using RMI, you must