Implementation of Remote Interface

Figure 4.1

Listing 4.2 GreaterServerImpl.java (Complete code)

import java.rmi.*;
import java.rmi.server.*;

//server class
public class GreaterServerImpl implements GreaterInterface{
	
  //constructor
  public GreaterServerImpl()
	throws RemoteException{
			
	System.out.println("Creating server object");
  }
	
  //remote method called by clients
  public String getGreater(int one,int two)
	throws RemoteException{
	if(one > two)
		return one +" is greater";
	else if(two > one)
		return two +" is greater" ;
	else 
		return "Equal" ;
  }
	
   //main method
    public static void main(String args[])
	throws Exception{
        
	//server instance
	 GreaterServerImpl obj = new GreaterServerImpl();
	 
	 //explicitly exporting remote object
	 UnicastRemoteObject.exportObject(obj);
	 
	 //bind with the registry service
	 Naming.rebind("Server",obj);
	}
}

Explanation of Code

Import necessary packages.

import java.rmi.*;
import java.rmi.server.*;

The implementation class declares which remote interface(s) it is implementing. Here is the GreaterServerImpl class declaration:

public class GreaterServerImpl 
	implements GreaterInterface{

The GreaterServerImpl class is not extending the UnicastRemoteObject.

The constructor for this class simply prints a small message.

//constructor
public GreaterServerImpl()
	throws RemoteException{
			
	System.out.println("Creating server object");
}

Here is the implementation for the getGreater() method, which compares two given numbers and returns the greater number.

//remote method called by clients
public String getGreater(int one,int two)
	throws RemoteException{
	if(one > two)
		return one +" is greater";
	else if(two > one)
		return two +" is greater" ;
	else 
		return "Equal" ;
}

The main method of the server creates one or more instances of the remote object implementation, which provides the service. For example:

GreaterServerImpl obj = new GreaterServerImpl();

The following line explicitly exports the remote object to make it available to receive incoming calls, using an anonymous port.

//explicitly exporting remote object
UnicastRemoteObject.exportObject(obj);

Rebinding the specified name to a remote object.

//bind with the regsitry service
Naming.rebind("Server",obj);