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The ActiveMQ Message Broker and Client implementations
/**
* 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;
/**
* Singelton, references maintained by users
* @version $Revision$
*/
public final class Scheduler {
private final Timer CLOCK_DAEMON = new Timer("ActiveMQ Scheduler", true);
private final HashMap TIMER_TASKS = new HashMap();
private static Scheduler instance;
static {
instance = new Scheduler();
}
private Scheduler() {
}
public static Scheduler getInstance() {
return instance;
}
public synchronized void executePeriodically(final Runnable task, long period) {
TimerTask timerTask = new SchedulerTimerTask(task);
CLOCK_DAEMON.scheduleAtFixedRate(timerTask, period, period);
TIMER_TASKS.put(task, timerTask);
}
/*
* execute on rough schedual based on termination of last execution. There is no
* compensation (two runs in quick succession) for delays
*/
public synchronized void schedualPeriodically(final Runnable task, long period) {
TimerTask timerTask = new SchedulerTimerTask(task);
CLOCK_DAEMON.schedule(timerTask, period, period);
TIMER_TASKS.put(task, timerTask);
}
public synchronized void cancel(Runnable task) {
TimerTask ticket = TIMER_TASKS.remove(task);
if (ticket != null) {
ticket.cancel();
CLOCK_DAEMON.purge();//remove cancelled TimerTasks
}
}
public void executeAfterDelay(final Runnable task, long redeliveryDelay) {
TimerTask timerTask = new SchedulerTimerTask(task);
CLOCK_DAEMON.schedule(timerTask, redeliveryDelay);
}
public void shutdown() {
CLOCK_DAEMON.cancel();
}
}