askremote.java

solve readers-writers problem with RMI

/*
################################################################################
# askRemote.java
#
# Copyright (C) 2007 Fernando G. Tinetti
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
################################################################################
 *
 * askRemote.java
 *    Expected to be used as a "client", behaving as a reader
 *    process or a writer process depending upon the "command
 *    line argument". 
 *    Access the resource by 5 secs. (hardcoded), this is the 
 *    elapsed time between the return from access...() and the
 *    call to leave...() 
 *    Used with 
 *               java askRemote <hostname> <Read/Write>
 *       <hostname>: hostname or IP of the host where the remote
 *                   object ("server") is "waiting"
 *       <Read/Write>: Read  ==> reader process
 *                     Write ==> writer process
 */


import java.rmi.Naming;                    /* lookup         */
import java.rmi.registry.Registry;         /* REGISTRY_PORT  */

import java.net.MalformedURLException;     /* Exceptions...  */
import java.rmi.NotBoundException;
import java.rmi.RemoteException;

import java.lang.Thread;                   /* Just to sleep  */

public class askRemote
{
  public static void main(String[] args)
  {
    System.out.println("Arguments received:");
    for (String s: args) {
      System.out.println("   " + s);
    }

    /* Look for hostname and msg length in the command line */
    if (args.length != 2)
    {
      System.out.println("2 arguments needed: (remote) hostname [Read/Write]");
      System.exit(1);
    }

    try {
      String rname = "//" + args[0] + ":" + Registry.REGISTRY_PORT + "/remote";

      // System.out.println("About to lookup for " + rname);

      remoteMethod remote = (remoteMethod) Naming.lookup(rname);

      if (args[1].compareTo("Read") == 0)
      {
        System.out.println("About to call accessReader");
        remote.accessReader();
        System.out.println("Reading...");
        Thread.currentThread().sleep(5000);
        System.out.println("About to call leaveReader");
        remote.leaveReader();
        System.out.println("Back from leaveReader");  
      }
      else if (args[1].compareTo("Write") == 0)
      {
        remote.accessWriter();
        System.out.println("Writing...");
        Thread.currentThread().sleep(5000);
        remote.leaveWriter();
      }
      else
      {
        System.out.println("2 arguments needed: (remote) hostname [Read/Write]");
        System.exit(1);
      }
      System.out.println("Done");

    } catch (MalformedURLException e) {
        e.printStackTrace();
    } catch (RemoteException e) {
        e.printStackTrace();
    } catch (NotBoundException e) {
        e.printStackTrace();
    } catch (Exception e) {
        e.printStackTrace();
    }
  }
}