// a simple remote database

// usage:
//   javac RemoteDatabase.java 
//   rmic RemoteDatabaseServer 
//   rmiregistry 9999 &
//   java RemoteDatabaseServer

// then start a client by executing
//   java Client rounds

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

// interface to the database
public interface RemoteDatabase extends Remote {
  public int read() throws RemoteException;
  public void write(int value) throws RemoteException;
}

// the database server
class RemoteDatabaseServer extends UnicastRemoteObject
          implements RemoteDatabase {
  protected int data = 0;  // the "database"

  public int read() throws RemoteException {
    return data;
  }

  public void write(int value) throws RemoteException {
    data = value;
    System.out.println("new value is: " + data);
  }

  // constructor required because of throws clause	    
  public RemoteDatabaseServer() throws RemoteException {
    super();
  }

  public static void main(String[] args) {
    try {
      // create a remote database server object
      RemoteDatabaseServer server = new RemoteDatabaseServer();
      
      // register name and start serving!
      String name = "rmi://localhost:9999/database";
      Naming.bind(name, server);
      System.out.println(name + " is running");
    }
    catch (Exception e) {
      System.err.println(e);
    }
  }
}

// a client
class Client {
  public static void main(String[] args) {
    try {
      // set the standard RMI security manager
      System.setSecurityManager(new RMISecurityManager());

      // get remote database object
      String name = "rmi://localhost:9999/database";
      RemoteDatabase db = (RemoteDatabase) Naming.lookup(name);

      // read command-line argument and access database
      int value, rounds = Integer.parseInt(args[0]);
      for (int i = 0; i < rounds; i++) {
        value = db.read();
        System.out.println("read: " + value);
        db.write(value+1);
      }
    }
    catch (Exception e) { 
      System.err.println(e);
    }
  }
}