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 */ 018 019package org.apache.commons.exec; 020 021import java.util.Enumeration; 022import java.util.Vector; 023 024/** 025 * Generalization of {@code ExecuteWatchdog} 026 * 027 * @see org.apache.commons.exec.ExecuteWatchdog 028 * 029 * @version $Id: Watchdog.java 1636056 2014-11-01 21:12:52Z ggregory $ 030 */ 031public class Watchdog implements Runnable { 032 033 private final Vector<TimeoutObserver> observers = new Vector<TimeoutObserver>(1); 034 035 private final long timeout; 036 037 private boolean stopped = false; 038 039 public Watchdog(final long timeout) { 040 if (timeout < 1) { 041 throw new IllegalArgumentException("timeout must not be less than 1."); 042 } 043 this.timeout = timeout; 044 } 045 046 public void addTimeoutObserver(final TimeoutObserver to) { 047 observers.addElement(to); 048 } 049 050 public void removeTimeoutObserver(final TimeoutObserver to) { 051 observers.removeElement(to); 052 } 053 054 protected final void fireTimeoutOccured() { 055 final Enumeration<TimeoutObserver> e = observers.elements(); 056 while (e.hasMoreElements()) { 057 e.nextElement().timeoutOccured(this); 058 } 059 } 060 061 public synchronized void start() { 062 stopped = false; 063 final Thread t = new Thread(this, "WATCHDOG"); 064 t.setDaemon(true); 065 t.start(); 066 } 067 068 public synchronized void stop() { 069 stopped = true; 070 notifyAll(); 071 } 072 073 public void run() { 074 final long startTime = System.currentTimeMillis(); 075 boolean isWaiting; 076 synchronized (this) { 077 long timeLeft = timeout - (System.currentTimeMillis() - startTime); 078 isWaiting = timeLeft > 0; 079 while (!stopped && isWaiting) { 080 try { 081 wait(timeLeft); 082 } catch (final InterruptedException e) { 083 } 084 timeLeft = timeout - (System.currentTimeMillis() - startTime); 085 isWaiting = timeLeft > 0; 086 } 087 } 088 089 // notify the listeners outside of the synchronized block (see EXEC-60) 090 if (!isWaiting) { 091 fireTimeoutOccured(); 092 } 093 } 094 095}