Simple RMI example

Here is a very simple RMI example. The writeup about RMI can be found in my previous post here.

Remote Interface

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

public interface Product extends Remote{
 
 public String getDescription() throws RemoteException;

}

Implementation of the Remote Interface:

import java.rmi.server.*;
import java.rmi.*;
import working.testing.myrmi.remoteinterface.*;

public class ProductImpl implements Product {
 
 private String type;
 
 public ProductImpl(String type)throws RemoteException{
  this.type = type; 
 }
 
 public String getDescription() throws RemoteException{
  return ("The Product is " + type);
 }
}

The Server

import java.rmi.*;
import java.rmi.server.*;
import java.rmi.registry.*;
import working.testing.myrmi.remoteinterface.*;

public class MyRMIServer {

 public static void main(String[] args) {
  String toaster = "toaster";
  try {
   /** If an RMI program does not install a 
    *  security manager, RMI will not download 
    *  classes (other than from the local class path) 
    *  for objects received as arguments or 
    *  return values of remote method invocations.
    */
   if (System.getSecurityManager() == null) {
       System.setSecurityManager
        (new RMISecurityManager());
   }
   Product product = new ProductImpl(toaster);
   /** 
    * Since the server dosent extend
    * UnicastRemoteObject,
    * First we need to export the
    * object. Once the remote object has been
    * successfully exported it is ready for
    * invocations. However for clients to 
    * invoke the remote object, it needs to
    * be bound to the registry with a name.
    * If extending UnicastRemoteObject,
    * We should do only the following
    * Naming.rebind(toaster,product); 
    * because it automatically exports 
    * the remote object for us 
    */
   Product stub = (Product)UnicastRemoteObject.
      exportObject(product,0);
   Registry registry = LocateRegistry.createRegistry(5555);
   registry.rebind(toaster,stub);
   System.out.println("Waiting for clients");
  } catch (Exception e) {
   System.out.println("The Exception is " + e);
   e.printStackTrace();
  }

 }

}

The client

import working.testing.myrmi.remoteinterface.*;
import java.rmi.*;
import java.rmi.registry.*;

public class MyRMIClient {

 public static void main(String[] args) {
  try {
   /** If an RMI program does not install a 
    *  security manager, RMI will not download 
    *  classes (other than from the local class path) 
    *  for objects received as arguments or 
    *  return values of remote method invocations.
    */
   if (System.getSecurityManager() == null) {
       System.setSecurityManager
        (new RMISecurityManager());
   }
   
   /** 
    * First we need to get a handle
    * to the registry on the server machine and
    * then we need to lookup for the remote
    * object
    * We can also do
    * Product product = 
    * (Product)Naming.lookup
    * ("rmi://host:1099/toaster");
    * where host is the hostname where 
    * the server is running. 
    * host will be localhost if the server is
    * running locally. Sometimes putting in 
    * localhost can cause
    * some unnecessary exceptions, so just do
    * lookup("rmi://:1099/toaster") if
    * on localhost 
    * Also while getting registry if on localhost
    * better to do just getRegistry() instead of
    * getRegistry("localhost") to avoid similar
    * exceptions as above.
    */
   Registry registry = LocateRegistry.
      getRegistry(5555); 
   Product product = (Product)registry.
       lookup("toaster");
   /*Product product = (Product)Naming.
     lookup("rmi://:1099/toaster");*/
   System.out.println(product.getDescription());
  } catch (Exception e) {
   System.out.println("The exception is " + e);
   e.printStackTrace();
  }
 }
}