001    /**
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.activemq.thread;
018    
019    import java.util.HashMap;
020    import java.util.Timer;
021    import java.util.TimerTask;
022    
023    import org.apache.activemq.util.ServiceStopper;
024    import org.apache.activemq.util.ServiceSupport;
025    
026    /**
027     *
028     */
029    public final class Scheduler extends ServiceSupport {
030        private final String name;
031        private Timer timer;
032        private final HashMap<Runnable, TimerTask> timerTasks = new HashMap<Runnable, TimerTask>();
033    
034        public Scheduler (String name) {
035            this.name = name;
036        }
037    
038        public void executePeriodically(final Runnable task, long period) {
039            TimerTask timerTask = new SchedulerTimerTask(task);
040            timer.schedule(timerTask, period, period);
041            timerTasks.put(task, timerTask);
042        }
043    
044        /*
045         * execute on rough schedule based on termination of last execution. There is no
046         * compensation (two runs in quick succession) for delays
047         */
048        public synchronized void schedualPeriodically(final Runnable task, long period) {
049            TimerTask timerTask = new SchedulerTimerTask(task);
050            timer.schedule(timerTask, period, period);
051            timerTasks.put(task, timerTask);
052        }
053    
054        public synchronized void cancel(Runnable task) {
055            TimerTask ticket = timerTasks.remove(task);
056            if (ticket != null) {
057                ticket.cancel();
058                timer.purge(); // remove cancelled TimerTasks
059            }
060        }
061    
062        public synchronized void executeAfterDelay(final Runnable task, long redeliveryDelay) {
063            TimerTask timerTask = new SchedulerTimerTask(task);
064            timer.schedule(timerTask, redeliveryDelay);
065        }
066    
067        public void shutdown() {
068            timer.cancel();
069        }
070    
071        @Override
072        protected synchronized void doStart() throws Exception {
073            this.timer = new Timer(name, true);
074        }
075    
076        @Override
077        protected synchronized void doStop(ServiceStopper stopper) throws Exception {
078           if (this.timer != null) {
079               this.timer.cancel();
080           }
081        }
082    
083        public String getName() {
084            return name;
085        }
086    }