A pool of work threads : Thread Pool « Thread « Java Tutorial






/*
 * WorkThreadPool.java - Background thread pool that does stuff
 * :tabSize=8:indentSize=8:noTabs=false:
 * :folding=explicit:collapseFolds=1:
 *
 * Copyright (C) 2000 Slava Pestov
 *
 * 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 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., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

//{{{ Imports
import java.util.EventListener;

import javax.swing.SwingUtilities;
import javax.swing.event.EventListenerList;

//}}}

/**
 * A pool of work threads.
 * 
 * @author Slava Pestov
 * @version $Id: WorkThreadPool.java 12504 2008-04-22 23:12:43Z ezust $
 * @see org.gjt.sp.util.WorkThread
 * @since jEdit 2.6pre1
 */
public class WorkThreadPool {
  // {{{ WorkThreadPool constructor
  /**
   * Creates a new work thread pool with the specified number of work threads.
   * 
   * @param name
   *          The thread name prefix
   * @param count
   *          The number of work threads
   */
  public WorkThreadPool(String name, int count) {
    listenerList = new EventListenerList();

    if (count != 0) {
      threadGroup = new ThreadGroup(name);
      threads = new WorkThread[count];
      for (int i = 0; i < threads.length; i++) {
        threads[i] = new WorkThread(this, threadGroup, name + " #" + (i + 1));
      }
    }

  } // }}}

  // {{{ start() method
  /**
   * Starts all the threads in this thread pool.
   */
  public void start() {
    /* not really needed since threads don't start until after */
    synchronized (lock) {
      started = true;

      if (awtRequestCount != 0 && requestCount == 0)
        queueAWTRunner();
    }

    if (threads != null) {
      for (int i = 0; i < threads.length; i++) {
        threads[i].start();
      }
    }
  } // }}}

  // {{{ addWorkRequest() method
  /**
   * Adds a work request to the queue.
   * 
   * @param run
   *          The runnable
   * @param inAWT
   *          If true, will be executed in AWT thread. Otherwise, will be
   *          executed in work thread
   */
  public void addWorkRequest(Runnable run, boolean inAWT) {
    if (threads == null) {
      run.run();
      return;
    }

    synchronized (lock) {
      // {{{ if there are no requests, execute AWT requests immediately
      if (started && inAWT && requestCount == 0 && awtRequestCount == 0) {
        // Log.log(Log.DEBUG,this,"AWT immediate: " + run);

        if (SwingUtilities.isEventDispatchThread())
          run.run();
        else
          SwingUtilities.invokeLater(run);

        return;
      } // }}}

      Request request = new Request(run);

      // {{{ Add to AWT queue...
      if (inAWT) {
        if (firstAWTRequest == null && lastAWTRequest == null)
          firstAWTRequest = lastAWTRequest = request;
        else {
          lastAWTRequest.next = request;
          lastAWTRequest = request;
        }

        awtRequestCount++;

        // if no requests are running, requestDone()
        // will not be called, so we must queue the
        // AWT runner ourselves.
        if (started && requestCount == 0)
          queueAWTRunner();
      } // }}}
      // {{{ Add to work thread queue...
      else {
        if (firstRequest == null && lastRequest == null)
          firstRequest = lastRequest = request;
        else {
          lastRequest.next = request;
          lastRequest = request;
        }

        requestCount++;
      } // }}}

      lock.notifyAll();
    }
  } // }}}

  // {{{ waitForRequests() method
  /**
   * Waits until all requests are complete.
   */
  public void waitForRequests() {
    if (threads == null)
      return;

    synchronized (waitForAllLock) {
      while (requestCount != 0) {
        try {
          waitForAllLock.wait();
        } catch (InterruptedException ie) {

        }
      }
    }

    if (SwingUtilities.isEventDispatchThread()) {
      // do any queued AWT runnables
      doAWTRequests();
    } else {
      try {
        SwingUtilities.invokeAndWait(new RunRequestsInAWTThread());
      } catch (Exception e) {

      }
    }
  } // }}}

  // {{{ getRequestCount() method
  /**
   * Returns the number of pending requests.
   * 
   * @return the pending request count
   */
  public int getRequestCount() {
    return requestCount;
  } // }}}

  // {{{ getThreadCount() method
  /**
   * Returns the number of threads in this pool.
   * 
   * @return the thread count
   */
  public int getThreadCount() {
    if (threads == null)
      return 0;
    else
      return threads.length;
  } // }}}

  // {{{ getThread() method
  /**
   * Returns the specified thread.
   * 
   * @param index
   *          The index of the thread
   * @return a WorkThread
   */
  public WorkThread getThread(int index) {
    return threads[index];
  } // }}}

  // {{{ addProgressListener() method
  /**
   * Adds a progress listener to this thread pool.
   * 
   * @param listener
   *          The listener
   */
  public void addProgressListener(WorkThreadProgressListener listener) {
    listenerList.add(WorkThreadProgressListener.class, listener);
  } // }}}

  // {{{ removeProgressListener() method
  /**
   * Removes a progress listener from this thread pool.
   * 
   * @param listener
   *          The listener
   */
  public void removeProgressListener(WorkThreadProgressListener listener) {
    listenerList.remove(WorkThreadProgressListener.class, listener);
  } // }}}

  // {{{ Package-private members
  final Object lock = new Object();

  final Object waitForAllLock = new Object();

  // {{{ fireStatusChanged() method
  void fireStatusChanged(WorkThread thread) {
    final Object[] listeners = listenerList.getListenerList();
    if (listeners.length != 0) {
      int index = 0;
      for (int i = 0; i < threads.length; i++) {
        if (threads[i] == thread) {
          index = i;
          break;
        }
      }

      for (int i = listeners.length - 2; i >= 0; i--) {
        if (listeners[i] == WorkThreadProgressListener.class) {
          ((WorkThreadProgressListener) listeners[i + 1]).statusUpdate(WorkThreadPool.this, index);
        }
      }
    }
  } // }}}

  // {{{ fireProgressChanged() method
  void fireProgressChanged(WorkThread thread) {
    final Object[] listeners = listenerList.getListenerList();
    if (listeners.length != 0) {
      int index = 0;
      for (int i = 0; i < threads.length; i++) {
        if (threads[i] == thread) {
          index = i;
          break;
        }
      }

      for (int i = listeners.length - 2; i >= 0; i--) {
        if (listeners[i] == WorkThreadProgressListener.class) {
          ((WorkThreadProgressListener) listeners[i + 1])
              .progressUpdate(WorkThreadPool.this, index);
        }
      }
    }
  } // }}}

  // {{{ requestDone() method
  void requestDone() {
    synchronized (lock) {
      requestCount--;

      if (requestCount == 0 && firstAWTRequest != null)
        queueAWTRunner();
    }
  } // }}}

  // {{{ getNextRequest() method
  Request getNextRequest() {
    synchronized (lock) {
      Request request = firstRequest;
      if (request == null)
        return null;

      firstRequest = firstRequest.next;
      if (firstRequest == null)
        lastRequest = null;

      if (request.alreadyRun)
        throw new InternalError("AIEE!!! Request run twice!!! " + request.run);
      request.alreadyRun = true;

      /*
       * StringBuffer buf = new StringBuffer("request queue is now: "); Request
       * _request = request.next; while(_request != null) {
       * buf.append(_request.id); if(_request.next != null) buf.append(",");
       * _request = _request.next; } Log.log(Log.DEBUG,this,buf.toString());
       */

      return request;
    }
  } // }}}

  // }}}

  // {{{ Private members

  // {{{ Instance variables
  private boolean started;

  private ThreadGroup threadGroup;

  private WorkThread[] threads;

  // Request queue
  private Request firstRequest;

  private Request lastRequest;

  private int requestCount;

  // AWT thread magic
  private boolean awtRunnerQueued;

  private Request firstAWTRequest;

  private Request lastAWTRequest;

  private int awtRequestCount;

  private EventListenerList listenerList;

  // }}}

  // {{{ doAWTRequests() method
  /** Must always be called with the lock held. */
  private void doAWTRequests() {
    while (requestCount == 0 && firstAWTRequest != null) {
      doAWTRequest(getNextAWTRequest());
    }
  } // }}}

  // {{{ doAWTRequest() method
  /**
   * Must always be called with the lock held.
   * 
   * @param request
   *          the request to run
   */
  private void doAWTRequest(Request request) {
    // Log.log(Log.DEBUG,this,"Running in AWT thread: " + request);

    try {
      request.run.run();
    } catch (Throwable t) {
    }

    awtRequestCount--;
  } // }}}

  // {{{ queueAWTRunner() method
  /** Must always be called with the lock held. */
  private void queueAWTRunner() {
    if (!awtRunnerQueued) {
      awtRunnerQueued = true;
      SwingUtilities.invokeLater(new RunRequestsInAWTThread());
      // Log.log(Log.DEBUG,this,"AWT runner queued");
    }
  } // }}}

  // {{{ getNextAWTRequest() method
  private Request getNextAWTRequest() {
    Request request = firstAWTRequest;
    firstAWTRequest = firstAWTRequest.next;
    if (firstAWTRequest == null)
      lastAWTRequest = null;

    if (request.alreadyRun)
      throw new InternalError("AIEE!!! Request run twice!!! " + request.run);
    request.alreadyRun = true;

    /*
     * StringBuffer buf = new StringBuffer("AWT request queue is now: ");
     * Request _request = request.next; while(_request != null) {
     * buf.append(_request.id); if(_request.next != null) buf.append(",");
     * _request = _request.next; } Log.log(Log.DEBUG,this,buf.toString());
     */

    return request;
  } // }}}

  // }}}

  static int ID;

  // {{{ Request class
  static class Request {
    int id = ++ID;

    Runnable run;

    boolean alreadyRun;

    Request next;

    Request(Runnable run) {
      this.run = run;
    }

    public String toString() {
      return "[id=" + id + ",run=" + run + "]";
    }
  } // }}}

  // {{{ RunRequestsInAWTThread class
  class RunRequestsInAWTThread implements Runnable {
    public void run() {
      synchronized (lock) {
        awtRunnerQueued = false;
        if (requestCount == 0)
          doAWTRequests();
      }
    }
  } // }}}
}

/*
 * WorkThread.java - Background thread that does stuff Copyright (C) 2000 Slava
 * Pestov
 * 
 * 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 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., 59 Temple
 * Place - Suite 330, Boston, MA 02111-1307, USA.
 */

/**
 * Services work requests in the background.
 * 
 * @author Slava Pestov
 * @version $Id: WorkThread.java 12504 2008-04-22 23:12:43Z ezust $
 */
class WorkThread extends Thread implements ThreadAbortMonitor {
  public WorkThread(WorkThreadPool pool, ThreadGroup group, String name) {
    super(group, name);
    // so that jEdit doesn't exit with no views open automatically
    // setDaemon(true);
    setPriority(Thread.MIN_PRIORITY);

    this.pool = pool;
  }

  /**
   * Sets if the current request can be aborted. If set to true and already
   * aborted, the thread will be stopped
   * 
   * @param abortable
   *          true if the WorkThread is abortable
   * @since jEdit 2.6pre1
   */
  public void setAbortable(boolean abortable) {
    synchronized (abortLock) {
      this.abortable = abortable;
      if (aborted)
        stop(new Abort());
    }
  }

  /**
   * Returns if the work thread is currently running a request.
   * 
   * @return true if a request is currently running
   */
  public boolean isRequestRunning() {
    return requestRunning;
  }

  public boolean isAborted() {
    synchronized (abortLock) {
      return aborted;
    }
  }

  /**
   * Returns the status text.
   * 
   * @return the status label
   */
  public String getStatus() {
    return status;
  }

  /**
   * Sets the status text.
   * 
   * @param status
   *          the new status of the thread
   * @since jEdit 2.6pre1
   */
  public void setStatus(String status) {
    this.status = status;
    pool.fireProgressChanged(this);
  }

  /**
   * Returns the progress value.
   * 
   * @return the progress value
   */
  public int getProgressValue() {
    return progressValue;
  }

  /**
   * Sets the progress value.
   * 
   * @param progressValue
   *          the new progress value
   * @since jEdit 2.6pre1
   */
  public void setProgressValue(int progressValue) {
    this.progressValue = progressValue;
    pool.fireProgressChanged(this);
  }

  /**
   * Returns the progress maximum.
   * 
   * @return the maximum value of the progression
   */
  public int getProgressMaximum() {
    return progressMaximum;
  }

  /**
   * Sets the maximum progress value.
   * 
   * @param progressMaximum
   *          the maximum value of the progression
   * @since jEdit 2.6pre1
   */
  public void setProgressMaximum(int progressMaximum) {
    this.progressMaximum = progressMaximum;
    pool.fireProgressChanged(this);
  }

  /**
   * Aborts the currently running request, if allowed.
   * 
   * @since jEdit 2.6pre1
   */
  public void abortCurrentRequest() {
    synchronized (abortLock) {
      if (abortable && !aborted)
        stop(new Abort());
      aborted = true;
    }
  }

  public void run() {

    for (;;) {
      doRequests();
    }
  }

  // private members
  private WorkThreadPool pool;

  private final Object abortLock = new Object();

  private boolean requestRunning;

  private boolean abortable;

  private boolean aborted;

  private String status;

  private int progressValue;

  private int progressMaximum;

  private void doRequests() {
    WorkThreadPool.Request request;
    for (;;) {
      request = pool.getNextRequest();
      if (request == null)
        break;
      else {
        requestRunning = true;
        pool.fireStatusChanged(this);
        doRequest(request);
        requestRunning = false;
      }
    }

    pool.fireStatusChanged(this);

    synchronized (pool.waitForAllLock) {
      // notify a running waitForRequests() method
      pool.waitForAllLock.notifyAll();
    }

    synchronized (pool.lock) {
      // wait for more requests
      try {
        pool.lock.wait();
      } catch (InterruptedException ie) {

      }
    }
  }

  private void doRequest(WorkThreadPool.Request request) {

    try {
      request.run.run();
    } catch (Throwable t) {

    } finally {
      synchronized (abortLock) {
        aborted = abortable = false;
      }
      status = null;
      progressValue = progressMaximum = 0;
      pool.requestDone();
      pool.fireStatusChanged(this);
    }
  }

  public static class Abort extends Error {
    public Abort() {
      super("Work request aborted");
    }
  }
}

/*
 * ThreadAbortMonitor.java - Thread Abort Monitor
 * :tabSize=8:indentSize=8:noTabs=false: :folding=explicit:collapseFolds=1:
 * 
 * Copyright (C) 2006 Matthieu Casanova
 * 
 * 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 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., 59 Temple
 * Place - Suite 330, Boston, MA 02111-1307, USA.
 */

/**
 * @author Matthieu Casanova
 * @author $Id: VFS.java 7129 2006-09-25 20:05:57Z kpouer $
 */
interface ThreadAbortMonitor {
  boolean isAborted();
}

/*
 * WorkThreadProgressListener.java - Progress listener Copyright (C) 2000 Slava
 * Pestov
 * 
 * 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 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., 59 Temple
 * Place - Suite 330, Boston, MA 02111-1307, USA.
 */

/**
 * A work thread execution progress listener.
 * 
 * @since jEdit 2.6pre1
 */
interface WorkThreadProgressListener extends EventListener {
  // status message changed, operation started, operation ends, ...
  void statusUpdate(WorkThreadPool threadPool, int threadIndex);

  // progress bar value change
  void progressUpdate(WorkThreadPool threadPool, int threadIndex);
}








10.22.Thread Pool
10.22.1.A pool of work threads
10.22.2.Simple thread pool. A task is executed by obtaining a thread from the pool