| /* |
| * 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.commons.exec; |
| |
| import java.util.Enumeration; |
| import java.util.Vector; |
| |
| /** |
| * Destroys all registered <code>Process</code>es when the VM exits. |
| * |
| * @version $Id$ |
| */ |
| public class ShutdownHookProcessDestroyer implements ProcessDestroyer, Runnable { |
| |
| /** the list of currently running processes */ |
| private final Vector<Process> processes = new Vector<Process>(); |
| |
| /** The thread registered at the JVM to execute the shutdown handler */ |
| private ProcessDestroyerImpl destroyProcessThread = null; |
| |
| /** Whether or not this ProcessDestroyer has been registered as a shutdown hook */ |
| private boolean added = false; |
| |
| /** |
| * Whether or not this ProcessDestroyer is currently running as shutdown hook |
| */ |
| private volatile boolean running = false; |
| |
| private class ProcessDestroyerImpl extends Thread { |
| |
| private boolean shouldDestroy = true; |
| |
| public ProcessDestroyerImpl() { |
| super("ProcessDestroyer Shutdown Hook"); |
| } |
| |
| @Override |
| public void run() { |
| if (shouldDestroy) { |
| ShutdownHookProcessDestroyer.this.run(); |
| } |
| } |
| |
| public void setShouldDestroy(final boolean shouldDestroy) { |
| this.shouldDestroy = shouldDestroy; |
| } |
| } |
| |
| /** |
| * Constructs a <code>ProcessDestroyer</code> and obtains |
| * <code>Runtime.addShutdownHook()</code> and |
| * <code>Runtime.removeShutdownHook()</code> through reflection. The |
| * ProcessDestroyer manages a list of processes to be destroyed when the VM |
| * exits. If a process is added when the list is empty, this |
| * <code>ProcessDestroyer</code> is registered as a shutdown hook. If |
| * removing a process results in an empty list, the |
| * <code>ProcessDestroyer</code> is removed as a shutdown hook. |
| */ |
| public ShutdownHookProcessDestroyer() { |
| } |
| |
| /** |
| * Registers this <code>ProcessDestroyer</code> as a shutdown hook, uses |
| * reflection to ensure pre-JDK 1.3 compatibility. |
| */ |
| private void addShutdownHook() { |
| if (!running) { |
| destroyProcessThread = new ProcessDestroyerImpl(); |
| Runtime.getRuntime().addShutdownHook(destroyProcessThread); |
| added = true; |
| } |
| } |
| |
| /** |
| * Removes this <code>ProcessDestroyer</code> as a shutdown hook, uses |
| * reflection to ensure pre-JDK 1.3 compatibility |
| */ |
| private void removeShutdownHook() { |
| if (added && !running) { |
| final boolean removed = Runtime.getRuntime().removeShutdownHook( |
| destroyProcessThread); |
| if (!removed) { |
| System.err.println("Could not remove shutdown hook"); |
| } |
| /* |
| * start the hook thread, a unstarted thread may not be eligible for |
| * garbage collection Cf.: http://developer.java.sun.com/developer/ |
| * bugParade/bugs/4533087.html |
| */ |
| |
| destroyProcessThread.setShouldDestroy(false); |
| destroyProcessThread.start(); |
| // this should return quickly, since it basically is a NO-OP. |
| try { |
| destroyProcessThread.join(20000); |
| } catch (final InterruptedException ie) { |
| // the thread didn't die in time |
| // it should not kill any processes unexpectedly |
| } |
| destroyProcessThread = null; |
| added = false; |
| } |
| } |
| |
| /** |
| * Returns whether or not the ProcessDestroyer is registered as as shutdown |
| * hook |
| * |
| * @return true if this is currently added as shutdown hook |
| */ |
| public boolean isAddedAsShutdownHook() { |
| return added; |
| } |
| |
| /** |
| * Returns <code>true</code> if the specified <code>Process</code> was |
| * successfully added to the list of processes to destroy upon VM exit. |
| * |
| * @param process |
| * the process to add |
| * @return <code>true</code> if the specified <code>Process</code> was |
| * successfully added |
| */ |
| public boolean add(final Process process) { |
| synchronized (processes) { |
| // if this list is empty, register the shutdown hook |
| if (processes.size() == 0) { |
| addShutdownHook(); |
| } |
| processes.addElement(process); |
| return processes.contains(process); |
| } |
| } |
| |
| /** |
| * Returns <code>true</code> if the specified <code>Process</code> was |
| * successfully removed from the list of processes to destroy upon VM exit. |
| * |
| * @param process |
| * the process to remove |
| * @return <code>true</code> if the specified <code>Process</code> was |
| * successfully removed |
| */ |
| public boolean remove(final Process process) { |
| synchronized (processes) { |
| final boolean processRemoved = processes.removeElement(process); |
| if (processRemoved && processes.size() == 0) { |
| removeShutdownHook(); |
| } |
| return processRemoved; |
| } |
| } |
| |
| /** |
| * Returns the number of registered processes. |
| * |
| * @return the number of register process |
| */ |
| public int size() { |
| return processes.size(); |
| } |
| |
| /** |
| * Invoked by the VM when it is exiting. |
| */ |
| public void run() { |
| synchronized (processes) { |
| running = true; |
| final Enumeration<Process> e = processes.elements(); |
| while (e.hasMoreElements()) { |
| final Process process = e.nextElement(); |
| try { |
| process.destroy(); |
| } |
| catch (final Throwable t) { |
| System.err.println("Unable to terminate process during process shutdown"); |
| } |
| } |
| } |
| } |
| } |