# WaitingThread.java

    /*
    ** Module   : WaitingThread.java
    ** Abstract : represents a waiting thread
    **
    ** Copyright (c) 2005-2017, Golden Code Development Corporation.
    **
    ** -#- -I- --Date-- --JPRM-- ----------------Description-----------------
    ** 001 SIY 20050113   @19509 Created initial version.
    ** 002 SIY 20050207   @19711 Allow delivering of the exception in case of
    **                           protocol error or queue termination.
    ** 003 SIY 20050315   @20396 Minor cleanups.
    ** 004 NVS 20060208   @24476 Added control flow calls. Changed
    **                           constructor.
    ** 005 GES 20060728   @28211 Reduced footprint and changed signatures to
    **                           pass some state that is easily available in
    **                           the caller and which greatly improves our
    **                           performance.
    ** 006 GES 20060811   @28568 Moved Control push/pop back to the caller
    **                           to eliminate a race condition.
    ** 007 CA  20120227          Do not wait if either the exception (or the
    **                           message) is already received.
    */
    /*
    ** This program is free software: you can redistribute it and/or modify
    ** it under the terms of the GNU Affero General Public License as
    ** published by the Free Software Foundation, either version 3 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 Affero General Public License for more details.
    **
    ** You may find a copy of the GNU Affero GPL version 3 at the following
    ** location: https://www.gnu.org/licenses/agpl-3.0.en.html
    **
    ** Additional terms under GNU Affero GPL version 3 section 7:
    **
    **   Under Section 7 of the GNU Affero GPL version 3, the following additional
    **   terms apply to the works covered under the License.  These additional terms
    **   are non-permissive additional terms allowed under Section 7 of the GNU
    **   Affero GPL version 3 and may not be removed by you.
    **
    **   0. Attribution Requirement.
    **
    **     You must preserve all legal notices or author attributions in the covered
    **     work or Appropriate Legal Notices displayed by works containing the covered
    **     work.  You may not remove from the covered work any author or developer
    **     credit already included within the covered work.
    **
    **   1. No License To Use Trademarks.
    **
    **     This license does not grant any license or rights to use the trademarks
    **     Golden Code, FWD, any Golden Code or FWD logo, or any other trademarks
    **     of Golden Code Development Corporation. You are not authorized to use the
    **     name Golden Code, FWD, or the names of any author or contributor, for
    **     publicity purposes without written authorization.
    **
    **   2. No Misrepresentation of Affiliation.
    **
    **     You may not represent yourself as Golden Code Development Corporation or FWD.
    **
    **     You may not represent yourself for publicity purposes as associated with
    **     Golden Code Development Corporation, FWD, or any author or contributor to
    **     the covered work, without written authorization.
    **
    **   3. No Misrepresentation of Source or Origin.
    **
    **     You may not represent the covered work as solely your work.  All modified
    **     versions of the covered work must be marked in a reasonable way to make it
    **     clear that the modified work is not originating from Golden Code Development
    **     Corporation or FWD.  All modified versions must contain the notices of
    **     attribution required in this license.
    */

    package com.goldencode.p2j.net;

    /**
     * This class represents an container which is placed into Pool of Waiting
     * Threads (PWT). It also used as an object instance on which thread is put
     * into waiting state.
     *
     * @author SIY
     * @version 1.0
     */
    class WaitingThread
    {
       /** A reference to an exception which indicates a failure. */
       private Exception exception = null;

       /** A reference to the reply message. */
       private Message message = null;

       /**
        * Constructs an empty instance.
        */
       WaitingThread()
       {
       }

       /**
        * Notify waiting thread that a failure occurred.
        *
        * @param    exception
        *           An exception to deliver. If it is <code>null</code> then
        *           thread is awakened but an exception will not be thrown.
        */
       synchronized void notifyException(Exception exception)
       {
          this.exception = exception;
          notify();
       }

       /**
        * Notify waiting thread that the reply message that matched the request
        * message's ID has arrived.
        *
        * @param    message
        *           The reply message that was received.
        */
       synchronized void notifyMessage(Message message)
       {
          this.message = message;
          notify();
       }

       /**
        * Suspend calling thread and wait until a matching reply message is
        * received, an exception is thrown, an interruption occurs or there is
        * a timeout. If the timeout parameter is not 0 then the waiting time is
        * limited to at least that specified amount of time. If time is 0 then
        * the thread waits indefinitely (or until the application or the user's
        * session ends).  A reply matches if the request ID is the same as the
        * given request ID.
        *
        * @param    timeout
        *           Time to wait for reply message (milliseconds).
        *
        * @return   The reply message or <code>null</code> if no reply is
        *           received.
        *
        * @throws   InterruptedException
        *           Forwarded from <code>Object.wait()</code>.
        * @throws   Exception
        *           Any other failure.
        */
       synchronized Message waitMessage(int timeout)
       throws InterruptedException,
              Exception
       {
          // check if the reply has already arrived, if we wait in that case then
          // the notify() will never occur because that has already been
          // processed
          if (message == null && exception == null)
             wait(timeout);

          if (exception != null)
             throw exception;

          return message;
       }
    }