Java Distributed Computing

Java RMI

The Java Remote Method Invocation (RMI) package is a Java-centric scheme for distributed objects that is now a part of the core Java API. RMI offers some of the critical elements of a distributed object system for Java, plus some other features that are made possible by the fact that RMI is a Java-only system. RMI has object communication facilities that are analogous to CORBA’s IIOP, and its object serialization system provides a way for you to transfer or request an object instance by value from one remote process to another.

Remote Object Interfaces

Since RMI is a Java-only distributed object scheme, all object interfaces are written in Java. Client stubs and server skeletons are generated from this interface, but using a slightly different process than in CORBA. First, the interface for the remote object has to be written as extending the java.rmi.Remote interface. The Remote interface doesn’t introduce any methods to the object’s interface; it just serves to mark remote objects for the RMI system. Also, all methods in the interface must be declared as throwing the java.rmi.RemoteException . The RemoteException is the base class for many of the exceptions that RMI defines for remote operations, and the RMI engineers decided to expose the exception model in the interfaces of all RMI remote objects. This is one of the drawbacks of RMI: it requires you to alter an existing interface in order to apply it to a distributed environment.

Server Implementations

Once the ...