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org/springframework/scheduling/concurrent/ReschedulingRunnable.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.concurrent;

import java.util.Date;
import java.util.concurrent.Delayed;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

import org.springframework.scheduling.Trigger;
import org.springframework.scheduling.support.DelegatingErrorHandlingRunnable;
import org.springframework.scheduling.support.SimpleTriggerContext;
import org.springframework.util.ErrorHandler;

/**
 * Internal adapter that reschedules an underlying {@link Runnable} according
 * to the next execution time suggested by a given {@link Trigger}.
 *
 <p>Necessary because a native {@link ScheduledExecutorService} supports
 * delay-driven execution only. The flexibility of the {@link Trigger} interface
 * will be translated onto a delay for the next execution time (repeatedly).
 *
 @author Juergen Hoeller
 @author Mark Fisher
 @since 3.0
 */
class ReschedulingRunnable extends DelegatingErrorHandlingRunnable implements ScheduledFuture<Object> {

  private final Trigger trigger;

  private final SimpleTriggerContext triggerContext = new SimpleTriggerContext();

  private final ScheduledExecutorService executor;

  private volatile ScheduledFuture currentFuture;

  private volatile Date scheduledExecutionTime;

  private final Object triggerContextMonitor = new Object();


  public ReschedulingRunnable(Runnable delegate, Trigger trigger, ScheduledExecutorService executor, ErrorHandler errorHandler) {
    super(delegate, errorHandler);
    this.trigger = trigger;
    this.executor = executor;
  }


  public ScheduledFuture schedule() {
    synchronized (this.triggerContextMonitor) {
      this.scheduledExecutionTime = this.trigger.nextExecutionTime(this.triggerContext);
      if (this.scheduledExecutionTime == null) {
        return null;
      }
      long initialDelay = this.scheduledExecutionTime.getTime() - System.currentTimeMillis();
      this.currentFuture = this.executor.schedule(this, initialDelay, TimeUnit.MILLISECONDS);
      return this;
    }
  }

  @Override
  public void run() {
    Date actualExecutionTime = new Date();
    super.run();
    Date completionTime = new Date();
    synchronized (this.triggerContextMonitor) {
      this.triggerContext.update(this.scheduledExecutionTime, actualExecutionTime, completionTime);
    }
    if (!this.currentFuture.isCancelled()) {
      schedule();
    }
  }


  public boolean cancel(boolean mayInterruptIfRunning) {
    return this.currentFuture.cancel(mayInterruptIfRunning);
  }

  public boolean isCancelled() {
    return this.currentFuture.isCancelled();
  }

  public boolean isDone() {
    return this.currentFuture.isDone();
  }

  public Object get() throws InterruptedException, ExecutionException {
    return this.currentFuture.get();
  }

  public Object get(long timeout, TimeUnit unitthrows InterruptedException, ExecutionException, TimeoutException {
    return this.currentFuture.get(timeout, unit);
  }

  public long getDelay(TimeUnit unit) {
    return this.currentFuture.getDelay(unit);
  }

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

}