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org/springframework/scheduling/commonj/TimerManagerTaskScheduler.java
/*
 * Copyright 2002-2009 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.scheduling.commonj;

import java.util.Date;
import java.util.concurrent.Delayed;
import java.util.concurrent.FutureTask;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;

import commonj.timers.Timer;
import commonj.timers.TimerListener;

import org.springframework.scheduling.TaskScheduler;
import org.springframework.scheduling.Trigger;
import org.springframework.scheduling.support.SimpleTriggerContext;
import org.springframework.scheduling.support.TaskUtils;
import org.springframework.util.ErrorHandler;

/**
 * Implementation of Spring's {@link TaskScheduler} interface, wrapping
 * a CommonJ {@link commonj.timers.TimerManager}.
 *
 @author Juergen Hoeller
 @author Mark Fisher
 @since 3.0
 */
public class TimerManagerTaskScheduler extends TimerManagerAccessor implements TaskScheduler {

  private volatile ErrorHandler errorHandler;

  public void setErrorHandler(ErrorHandler errorHandler) {
    this.errorHandler = errorHandler;
  }

  public ScheduledFuture schedule(Runnable task, Trigger trigger) {
    return new ReschedulingTimerListener(errorHandlingTask(task, true), trigger).schedule();
  }

  public ScheduledFuture schedule(Runnable task, Date startTime) {
    TimerScheduledFuture futureTask = new TimerScheduledFuture(errorHandlingTask(task, false));
    Timer timer = getTimerManager().schedule(futureTask, startTime);
    futureTask.setTimer(timer);
    return futureTask;
  }

  public ScheduledFuture scheduleAtFixedRate(Runnable task, Date startTime, long period) {
    TimerScheduledFuture futureTask = new TimerScheduledFuture(errorHandlingTask(task, true));
    Timer timer = getTimerManager().scheduleAtFixedRate(futureTask, startTime, period);
    futureTask.setTimer(timer);
    return futureTask;
  }

  public ScheduledFuture scheduleAtFixedRate(Runnable task, long period) {
    TimerScheduledFuture futureTask = new TimerScheduledFuture(errorHandlingTask(task, true));
    Timer timer = getTimerManager().scheduleAtFixedRate(futureTask, 0, period);
    futureTask.setTimer(timer);
    return futureTask;
  }

  public ScheduledFuture scheduleWithFixedDelay(Runnable task, Date startTime, long delay) {
    TimerScheduledFuture futureTask = new TimerScheduledFuture(errorHandlingTask(task, true));
    Timer timer = getTimerManager().schedule(futureTask, startTime, delay);
    futureTask.setTimer(timer);
    return futureTask;
  }

  public ScheduledFuture scheduleWithFixedDelay(Runnable task, long delay) {
    TimerScheduledFuture futureTask = new TimerScheduledFuture(errorHandlingTask(task, true));
    Timer timer = getTimerManager().schedule(futureTask, 0, delay);
    futureTask.setTimer(timer);
    return futureTask;
  }

  private Runnable errorHandlingTask(Runnable delegate, boolean isRepeatingTask) {
    return TaskUtils.decorateTaskWithErrorHandler(delegate, this.errorHandler, isRepeatingTask);
  }


  /**
   * ScheduledFuture adapter that wraps a CommonJ Timer.
   */
  private static class TimerScheduledFuture extends FutureTask<Object> implements TimerListener, ScheduledFuture<Object> {

    protected transient Timer timer;

    protected transient boolean cancelled = false;

    public TimerScheduledFuture(Runnable runnable) {
      super(runnable, null);
    }

    public void setTimer(Timer timer) {
      this.timer = timer;
    }

    public void timerExpired(Timer timer) {
      runAndReset();
    }

    @Override
    public boolean cancel(boolean mayInterruptIfRunning) {
      boolean result = super.cancel(mayInterruptIfRunning);
      this.timer.cancel();
      this.cancelled = true;
      return result;
    }

    public long getDelay(TimeUnit unit) {
      return unit.convert(System.currentTimeMillis() this.timer.getScheduledExecutionTime(), TimeUnit.MILLISECONDS);
    }

    public int compareTo(Delayed other) {
      if (this == other) {
        return 0;
      }
      long diff = getDelay(TimeUnit.MILLISECONDS- other.getDelay(TimeUnit.MILLISECONDS);
      return (diff == ((diff < 0)? -1));
    }
  }


  /**
   * ScheduledFuture adapter for trigger-based rescheduling.
   */
  private class ReschedulingTimerListener extends TimerScheduledFuture {

    private final Trigger trigger;

    private final SimpleTriggerContext triggerContext = new SimpleTriggerContext();

    private volatile Date scheduledExecutionTime;

    public ReschedulingTimerListener(Runnable runnable, Trigger trigger) {
      super(runnable);
      this.trigger = trigger;
    }

    public ScheduledFuture schedule() {
      this.scheduledExecutionTime = this.trigger.nextExecutionTime(this.triggerContext);
      if (this.scheduledExecutionTime == null) {
        return null;
      }
      setTimer(getTimerManager().schedule(this, this.scheduledExecutionTime));
      return this;
    }

    @Override
    public void timerExpired(Timer timer) {
      Date actualExecutionTime = new Date();
      super.timerExpired(timer);
      Date completionTime = new Date();
      this.triggerContext.update(this.scheduledExecutionTime, actualExecutionTime, completionTime);
      if (!this.cancelled) {
        schedule();
      }
    }
  }

}