2.5 Implementing a Remote Interface

• The class usually extends java.rmi.server.UnicastRemoteObject, thereby inheriting the remote behavior provided by the classes java.rmi.server.RemoteObject and java.rmi.server.RemoteServer.
• The class can implement any number of remote interfaces.
• The class can extend another remote implementation class.
• The class can define methods that do not appear in the remote interface, but those methods can only be used locally and are not available remotely.

package mypackage;

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

public class BankAccountImpl
        extends UnicastRemoteObject
        implements BankAccount
{
        private float balance = 0.0;

        public BankAccountImpl(float initialBalance) 
                throws RemoteException 
        {
                balance = initialBalance;
        }
        public void deposit(float amount) throws RemoteException {
                ...
        }
        public void withdraw(float amount) throws OverdrawnException,
                RemoteException {
                ...
        }
        public float getBalance() throws RemoteException {
                ...
        }
}

Note:

• If necessary, a class that implements a remote interface can extend some other class besides java.rmi.server.UnicastRemoteObject. However, the implementation class must then assume the responsibility for exporting the object (taken care of by the UnicastRemoteObject constructor) and for implementing (if needed) the correct remote semantics of the hashCode, equals, and toString methods inherited from the java.lang.Object class.
• If you export a remote object without specifying a socket factory, or if you export the object with a version of the method UnicastRemoteObject.exportObject or the constructor UnicastRemoteObject that does not contain parameters of type RMIClientSocketFactory and RMIServerSocketFactory, then the remote object is exported to all local addresses. To export a remote object to a specific address, see the section RMI Socket Factories.