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