Java Examples in a Nutshell, 3rd Edition

Chapter 21. Remote Method Invocation

This chapter presents examples of the remote method invocation (RMI) capabilities of the java.rmi and java.rmi.server packages. Remote method invocation is a powerful technology for developing networked applications without having to worry about the low-level networking details. RMI transcends the client/server model of computing with a more general remote object model. In this model, the server defines objects that clients can use remotely. Clients invoke methods of a remote object exactly as if it were a local object running in the same virtual machine as the client. RMI hides the underlying mechanism for transporting method arguments and return values across the network. An argument or return value can be a primitive value or any Serializable object.

To develop an RMI-based application, you need to follow these steps:

1. Create an interface that extends the java.rmi.Remote interface. This interface defines the exported methods that the remote object implements (i.e., the methods the server implements and clients can invoke remotely). Each method in this interface must be declared to throw a java.rmi.RemoteException, which is the superclass of many more specific RMI exception classes. Every remote method must declare that it can throw a RemoteException, because there are quite a few things that can go wrong during the remote method invocation process over a network. (Actually, in Java 1.2 and later, this requirement is loosened: remote ...