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.kahadb.util;
018    
019    import java.util.HashMap;
020    import java.util.Timer;
021    import java.util.TimerTask;
022    
023    /**
024     * @version $Revision: 945524 $
025     */
026    public final class Scheduler {
027    
028        
029    
030            public static final Timer CLOCK_DAEMON = new Timer("KahaDB Scheduler", true);
031        private static final HashMap<Runnable, TimerTask> TIMER_TASKS = new HashMap<Runnable, TimerTask>();
032    
033        private Scheduler() {
034        }
035    
036        public static synchronized void executePeriodically(final Runnable task, long period) {
037            TimerTask timerTask = new SchedulerTimerTask(task);
038            CLOCK_DAEMON.scheduleAtFixedRate(timerTask, period, period);
039            TIMER_TASKS.put(task, timerTask);
040        }
041    
042        public static synchronized void cancel(Runnable task) {
043            TimerTask ticket = TIMER_TASKS.remove(task);
044            if (ticket != null) {
045                ticket.cancel();
046                CLOCK_DAEMON.purge();//remove cancelled TimerTasks
047            }
048        }
049    
050        public static void executeAfterDelay(final Runnable task, long redeliveryDelay) {
051            TimerTask timerTask = new SchedulerTimerTask(task);
052            CLOCK_DAEMON.schedule(timerTask, redeliveryDelay);
053        }
054        
055        public static void shutdown() {
056            CLOCK_DAEMON.cancel();
057        }
058    
059    }