I need to run multiple external programs concurrently using RMI objects.

Question

have a web based solutiion which uses a backend machine for some processing. I have a RMI based Java proram running on the backend machine and the web server talks with this backend machine through RMI. Now, on this backend machine, I need to call some external program using Process s = Runtime.getRuntime().exec(....). Since this is a web application, multiple clients will connect at the same time and I need to run this external program for multiple clients at the same time.
Here is what I do. I have a separate RMI object bound to registry for each client that connects to the web server. This RMI object implements runnable interface, since I can't extend this class from Thread (it already extends from UnicastRemoteObject). So each time I call upon a method from this object, only one process gets started and other objects need to wait till this process finishes.
I need to start multiple processes at the sametime so that other clients don't have to wait for this thread to finish.
Please let me know if anybody has any other solution than installing an application server on this backend machine.
Here is my code.
public class iLinkOnlineSession extends UnicastRemoteObject implements Session, Serializable, Runnable
  public iLinkOnlineSession(String sessName, String sessId, String rootLogs, String rootWrks) throws RemoteException
    setSessionId(sessId);
    setName(sessName);
    ROOT_LOGS = rootLogs;
    ROOT_WORKSPACE = rootWrks;
    searchKeys_ = new Vector();
    searchObjects_ = new Hashtable();
    Thread s = new Thread(this);
    s.start();
  public void run()
    System.out.println("running");
  public String checkLogin(String user, String passwd)
    String msg = "";
    String cmd = "iLinkOnlineLogin";
    cmd += " param "+ user + " param " + passwd;
    System.out.println("cmd: " + cmd);
    try
      Runtime run = Runtime.getRuntime();
      Process proc = run.exec(cmd);           // Call to the external program.
      InputStream in = proc.getInputStream();
      Reader inp = new InputStreamReader(in);
      BufferedReader rd = new BufferedReader(inp);
      String line = rd.readLine();
      while(line != null)
        System.out.println(line);
        msg += line;
        line = rd.readLine();       
      int res = proc.waitFor();
    }catch(Exception e)
         e.printStackTrace();
    System.out.println("Msg: " + msg);
    return msg;
  public String searchObject(String user, String passwd, String param1, String paramVal1, String param2, String paramVal2, String param3, String paramVal3, String relLev, String mfgLoc)
    String cmd = "iLinkOnlineSearch";
    cmd += " param " + user + " param " + passwd + " param " + getSessionId() + " param " + logFile_ + " param " + param1 + " param " + paramVal1 +
          " param " + param2 + " param " + paramVal2 + " param " + param3 + " param " + paramVal3 + " param "
          + relLev + " param " + mfgLoc;
    System.out.println("cmd: " + cmd);
    try
      Runtime run = Runtime.getRuntime();
      Process proc = run.exec(cmd);                // External program.
      InputStream in = proc.getInputStream();
      Reader inp = new InputStreamReader(in);
      BufferedReader rd = new BufferedReader(inp);
      FileWriter out = new FileWriter(resultFile_);
      System.out.println("Filename: "+resultFile_);
      BufferedWriter wout = new BufferedWriter(out);
      String line = rd.readLine();
       while(line != null)
        System.out.println(line);
        wout.write(line);
        wout.newLine();
        wout.flush();
        line = rd.readLine();
      int res = proc.waitFor();
      wout.close();
      if(res == 0)
        boolean ret = createResultTable();
        if(ret == true)
          return GlobalConstants.SUCCESS_MSG;
        else
          return GlobalConstants.ERROR_MSG;
    }catch(Exception e)
            e.printStackTrace();
    System.out.println("getting results");
    return GlobalConstants.ERROR_MSG;
  }

Answer 1

I guess I don't get it.
RMI servers are inherently multi-threaded, so why are you running separate servers for every client?