content: /**
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You 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.apache.activemq.thread;
  
  import java.util.HashMap;
  import java.util.Timer;
  import java.util.TimerTask;
  
  import org.apache.activemq.util.ServiceStopper;
  import org.apache.activemq.util.ServiceSupport;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   *
   */
  public final class Scheduler extends ServiceSupport {
  
      private static final Logger LOG  = LoggerFactory.getLogger(Scheduler.class);
      private final String name;
      private Timer timer;
      private final HashMap<Runnable, TimerTask> timerTasks = new HashMap<Runnable, TimerTask>();
  
      public Scheduler(String name) {
          this.name = name;
      }
  
      public synchronized void executePeriodically(final Runnable task, long period) {
          TimerTask existing = timerTasks.get(task);
          if (existing != null) {
              LOG.debug("Task {} already scheduled, cancelling and rescheduling", task);
              cancel(task);
          }
          TimerTask timerTask = new SchedulerTimerTask(task);
          timer.schedule(timerTask, period, period);
          timerTasks.put(task, timerTask);
      }
  
      public synchronized void cancel(Runnable task) {
          TimerTask ticket = timerTasks.remove(task);
          if (ticket != null) {
              ticket.cancel();
              timer.purge(); // remove cancelled TimerTasks
          }
      }
  
      public synchronized void executeAfterDelay(final Runnable task, long redeliveryDelay) {
          TimerTask timerTask = new SchedulerTimerTask(task);
          timer.schedule(timerTask, redeliveryDelay);
      }
  
      public void shutdown() {
          timer.cancel();
      }
  
      @Override
      protected synchronized void doStart() throws Exception {
          this.timer = new Timer(name, true);
      }
  
      @Override
      protected synchronized void doStop(ServiceStopper stopper) throws Exception {
          if (this.timer != null) {
              this.timer.cancel();
          }
      }
  
      public String getName() {
          return name;
      }
  }
  