RMI server startup exception

[adithya narayan]

Hi,

I have written a simple RMI program and compiled it using JDK 1.6_14. I am starting the rmi registry explicitly on a particular port which works properly. When i proceed to start the server where i am binding the remote object the program fails:

Here are the programs i have written:


Remote Interface

package com.pack.rmi;

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

public interface RemoteInterface extends Remote 
{
	Integer mul(Integer number1 ,Integer number2)throws RemoteException;
}

RemoteImpl class

package com.pack.rmi;

import java.rmi.RemoteException;

public class RemoteImpl extends java.rmi.server.UnicastRemoteObject implements RemoteInterface/*, RemoteRealIntfc1, RemoteRealIntfc2*/
{
	public RemoteImpl() throws RemoteException
	{
		super();
	}

	/*public Integer add(Integer number1 ,Integer number2)
	{
		return number1 + number2;
	}
	
	public Integer sub(Integer number1 ,Integer number2)
	{
		return number1 - number2;
	}*/
	
	public Integer mul(Integer number1 ,Integer number2)throws RemoteException
	{
		return number1 * number2;
	}
}

RemoteServer class

package com.pack.rmi;

import java.net.MalformedURLException;
import java.rmi.Naming;
import java.rmi.RemoteException;

public class RemoteServer extends java.rmi.server.RemoteServer 
{
	public RemoteServer() 
	{
		try {
			RemoteInterface remoteIntfc = new RemoteImpl();
			/*RemoteRealIntfc1 remoteRIntfc1 = (RemoteRealIntfc1) remoteIntfc; 
			RemoteRealIntfc2 remoteRIntfc2 = (RemoteRealIntfc2) remoteIntfc;*/
			
			Naming.rebind("rmi://localhost:12345", remoteIntfc);
			
		} catch (RemoteException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (MalformedURLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	
	public static void main(String[] args) {
		new RemoteServer();
	}
}

and the client

package com.pack.client;

import java.net.MalformedURLException;
import java.rmi.Naming;
import java.rmi.NotBoundException;
import java.rmi.RemoteException;

import com.pack.rmi.RemoteInterface;

public class HelloClient {

	/**
	 * @param args
	 */
	public static void main(String[] args) 
	{
		RemoteInterface remoteIntfc;
		try {
			remoteIntfc = (RemoteInterface)Naming.lookup("rmi://localhost:12345");
			/*RemoteRealIntfc1 remoteIntfc1 = (RemoteRealIntfc1)Naming.lookup("rmi://localhost:12345");
			RemoteRealIntfc2 remoteIntfc2 = (RemoteRealIntfc2)Naming.lookup("rmi://localhost:12345");
			System.out.println( remoteIntfc1.add(4, 3) ); 
			System.out.println( remoteIntfc2.sub(4, 5) );*/ 
			System.out.println( remoteIntfc.mul(3, 6) );
		} catch (MalformedURLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (RemoteException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (NotBoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} 
		 
	}

}

And the exception i am getting is as follows:

Exception in thread "main" java.lang.NullPointerException
        at java.util.Hashtable.put(Hashtable.java:399)
        at sun.rmi.registry.RegistryImpl.rebind(RegistryImpl.java:153)
        at sun.rmi.registry.RegistryImpl_Skel.dispatch(Unknown Source)
        at sun.rmi.server.UnicastServerRef.oldDispatch(UnicastServerRef.java:386)
        at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:250)
        at sun.rmi.transport.Transport$1.run(Transport.java:159)
        at java.security.AccessController.doPrivileged(Native Method)
        at sun.rmi.transport.Transport.serviceCall(Transport.java:155)
        at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:535)
        at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:790)
        at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:649)
        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
        at java.lang.Thread.run(Thread.java:619)
        at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(StreamRemoteCall.java:255)
        at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:233)
        at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:359)
        at sun.rmi.registry.RegistryImpl_Stub.rebind(Unknown Source)
        at java.rmi.Naming.rebind(Naming.java:160)
        at com.pack.rmi.RemoteServer.<init>(RemoteServer.java:16)
        at com.pack.rmi.RemoteServer.main(RemoteServer.java:28)

Another question i had was after Java 2 rmic creates only stubs but after reading the following documentation:
http://download.oracle.com/javase/1.5.0/docs/tooldocs/windows/rmic.html

I feel that we need not even create the stubs for client using 'rmic' command. Am i right ? Its all reflection i guess ?

Or if we have to create stubs then i guess we need to supply the created 'stub' to the client ?
Please correct me if i am missing something.


Thanks,
Adithya.