diff options
Diffstat (limited to 'framework/src/ant/apache-ant-1.9.6/src/main/org/apache/tools/ant/taskdefs/ProcessDestroyer.java')
| -rw-r--r-- | framework/src/ant/apache-ant-1.9.6/src/main/org/apache/tools/ant/taskdefs/ProcessDestroyer.java | 220 |
1 files changed, 220 insertions, 0 deletions
diff --git a/framework/src/ant/apache-ant-1.9.6/src/main/org/apache/tools/ant/taskdefs/ProcessDestroyer.java b/framework/src/ant/apache-ant-1.9.6/src/main/org/apache/tools/ant/taskdefs/ProcessDestroyer.java new file mode 100644 index 00000000..ba9c9d48 --- /dev/null +++ b/framework/src/ant/apache-ant-1.9.6/src/main/org/apache/tools/ant/taskdefs/ProcessDestroyer.java @@ -0,0 +1,220 @@ +/* + * 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.HashSet; +import java.util.Iterator; + +/** + * 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 HashSet processes = new HashSet(); + // 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(); + } + return processes.add(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.remove(process); + if (processRemoved && processes.size() == 0) { + removeShutdownHook(); + } + return processRemoved; + } + } + + /** + * Invoked by the VM when it is exiting. + */ + public void run() { + synchronized (processes) { + running = true; + Iterator e = processes.iterator(); + while (e.hasNext()) { + ((Process) e.next()).destroy(); + } + } + } +} |