Timeout Observer
/*
* 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.
*
*/
import java.util.Enumeration;
import java.util.Vector;
/**
* Generalization of <code>ExecuteWatchdog</code>
*
* @see org.apache.commons.exec.ExecuteWatchdog
*/
public class Watchdog implements Runnable {
private Vector observers = new Vector(1);
private final long timeout;
private boolean stopped = false;
public Watchdog(final long timeout) {
if (timeout < 1) {
throw new IllegalArgumentException("timeout must not be less than 1.");
}
this.timeout = timeout;
}
public void addTimeoutObserver(final TimeoutObserver to) {
observers.addElement(to);
}
public void removeTimeoutObserver(final TimeoutObserver to) {
observers.removeElement(to);
}
protected final void fireTimeoutOccured() {
Enumeration e = observers.elements();
while (e.hasMoreElements()) {
((TimeoutObserver) e.nextElement()).timeoutOccured(this);
}
}
public synchronized void start() {
stopped = false;
Thread t = new Thread(this, "WATCHDOG");
t.setDaemon(true);
t.start();
}
public synchronized void stop() {
stopped = true;
notifyAll();
}
public synchronized void run() {
final long until = System.currentTimeMillis() + timeout;
long now;
while (!stopped && until > (now = System.currentTimeMillis())) {
try {
wait(until - now);
} catch (InterruptedException e) {
}
}
if (!stopped) {
fireTimeoutOccured();
}
}
}
/**
* Interface for classes that want to be notified by Watchdog.
*
* @see org.apache.commons.exec.Watchdog
*/
interface TimeoutObserver {
/**
* Called when the watchdow times out.
*
* @param w
* the watchdog that timed out.
*/
void timeoutOccured(Watchdog w);
}
Related examples in the same category
