| /* |
| * 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.tools.ant.taskdefs; |
| |
| import java.lang.reflect.InvocationTargetException; |
| import java.lang.reflect.Method; |
| import java.util.Enumeration; |
| import java.util.Vector; |
| |
| /** |
| * Destroys all registered <code>Process</code>es when the VM exits. |
| * |
| * @since Ant 1.5 |
| */ |
| class ProcessDestroyer implements Runnable { |
| private static final int THREAD_DIE_TIMEOUT = 20000; |
| private Vector processes = new Vector(); |
| // methods to register and unregister shutdown hooks |
| private Method addShutdownHookMethod; |
| private Method removeShutdownHookMethod; |
| 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 boolean running = false; |
| |
| private class ProcessDestroyerImpl extends Thread { |
| private boolean shouldDestroy = true; |
| |
| public ProcessDestroyerImpl() { |
| super("ProcessDestroyer Shutdown Hook"); |
| } |
| public void run() { |
| if (shouldDestroy) { |
| ProcessDestroyer.this.run(); |
| } |
| } |
| |
| public void setShouldDestroy(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. |
| */ |
| ProcessDestroyer() { |
| try { |
| // check to see if the shutdown hook methods exists |
| // (support pre-JDK 1.3 and Non-Sun VMs) |
| Class[] paramTypes = {Thread.class}; |
| addShutdownHookMethod = |
| Runtime.class.getMethod("addShutdownHook", paramTypes); |
| |
| removeShutdownHookMethod = |
| Runtime.class.getMethod("removeShutdownHook", paramTypes); |
| // wait to add shutdown hook as needed |
| } catch (NoSuchMethodException e) { |
| // it just won't be added as a shutdown hook... :( |
| } catch (Exception e) { |
| e.printStackTrace(); |
| } |
| } |
| |
| /** |
| * Registers this <code>ProcessDestroyer</code> as a shutdown hook, |
| * uses reflection to ensure pre-JDK 1.3 compatibility. |
| */ |
| private void addShutdownHook() { |
| if (addShutdownHookMethod != null && !running) { |
| destroyProcessThread = new ProcessDestroyerImpl(); |
| Object[] args = {destroyProcessThread}; |
| try { |
| addShutdownHookMethod.invoke(Runtime.getRuntime(), args); |
| added = true; |
| } catch (IllegalAccessException e) { |
| e.printStackTrace(); |
| } catch (InvocationTargetException e) { |
| Throwable t = e.getTargetException(); |
| if (t != null && t.getClass() == IllegalStateException.class) { |
| // shutdown already is in progress |
| running = true; |
| } else { |
| e.printStackTrace(); |
| } |
| } |
| } |
| } |
| |
| /** |
| * Removes this <code>ProcessDestroyer</code> as a shutdown hook, |
| * uses reflection to ensure pre-JDK 1.3 compatibility |
| */ |
| private void removeShutdownHook() { |
| if (removeShutdownHookMethod != null && added && !running) { |
| Object[] args = {destroyProcessThread}; |
| try { |
| Boolean removed = |
| (Boolean) removeShutdownHookMethod.invoke( |
| Runtime.getRuntime(), |
| args); |
| if (!removed.booleanValue()) { |
| System.err.println("Could not remove shutdown hook"); |
| } |
| } catch (IllegalAccessException e) { |
| e.printStackTrace(); |
| } catch (InvocationTargetException e) { |
| Throwable t = e.getTargetException(); |
| if (t != null && t.getClass() == IllegalStateException.class) { |
| // shutdown already is in progress |
| running = true; |
| } else { |
| e.printStackTrace(); |
| } |
| } |
| // 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); |
| if (!destroyProcessThread.getThreadGroup().isDestroyed()) { |
| // start() would throw IllegalThreadStateException from |
| // ThreadGroup.add if it were destroyed |
| destroyProcessThread.start(); |
| } |
| // this should return quickly, since it basically is a NO-OP. |
| try { |
| destroyProcessThread.join(THREAD_DIE_TIMEOUT); |
| } catch (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(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(Process process) { |
| synchronized (processes) { |
| boolean processRemoved = processes.removeElement(process); |
| if (processRemoved && processes.size() == 0) { |
| removeShutdownHook(); |
| } |
| return processRemoved; |
| } |
| } |
| |
| /** |
| * Invoked by the VM when it is exiting. |
| */ |
| public void run() { |
| synchronized (processes) { |
| running = true; |
| Enumeration e = processes.elements(); |
| while (e.hasMoreElements()) { |
| ((Process) e.nextElement()).destroy(); |
| } |
| } |
| } |
| } |