Java RMI Overview

What is Java RMI

Java Remote Method Invocation is a Java API that performs object-oriented equivalent of remote procedure calls, with support for direct transfer of serialized Java classes and distributed GC. RMI can be seen as the process of activating a method on remote running object.

At a high-level prospective, Java RMI consists of several well-split layers:

Application Layer

Provides remote interface.
Stub/Proxy Layer

This layer automatically handles method invocation marshalling and unmarshalling, network transmission.
Remote Reference Layer
Transport Layer

Provides TCP-based communication for RPC.

Example

Remote Interface

Defines methods callable remotely.

Remote Interface

import java.rmi.Remote;
import java.rmi.RemoteException;

public interface HelloService extends Remote {
    String sayHello(String name) throws RemoteException;
}

Remote Object Implementation

Implement the interface defined and extend the remote object class.

Remote Object

import java.rmi.server.UnicastRemoteObject;
import java.rmi.RemoteException;

public class HelloServiceImpl extends UnicastRemoteObject
                              implements HelloService {

    protected HelloServiceImpl() throws RemoteException {
        super();
    }

    @Override
    public String sayHello(String name) {
        return "Hello, " + name;
    }
}