1 /* 2 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 package java.lang; 26 27 import java.util.*; 28 29 /* 30 * Class to track and run user level shutdown hooks registered through 31 * <tt>{@link Runtime#addShutdownHook Runtime.addShutdownHook}</tt>. 32 * 33 * @see java.lang.Runtime#addShutdownHook 34 * @see java.lang.Runtime#removeShutdownHook 35 */ 36 37 class ApplicationShutdownHooks { 38 /* The set of registered hooks */ 39 private static IdentityHashMap<Thread, Thread> hooks; 40 static { 41 try { 42 Shutdown.add(1 /* shutdown hook invocation order */, 43 false /* not registered if shutdown in progress */, 44 new Runnable() { 45 public void run() { 46 runHooks(); 47 } 48 } 49 ); 50 hooks = new IdentityHashMap<>(); 51 } catch (IllegalStateException e) { 52 // application shutdown hooks cannot be added if 53 // shutdown is in progress. 54 hooks = null; 55 } 56 } 57 58 ApplicationShutdownHooks()59 private ApplicationShutdownHooks() {} 60 61 /* Add a new shutdown hook. Checks the shutdown state and the hook itself, 62 * but does not do any security checks. 63 */ add(Thread hook)64 static synchronized void add(Thread hook) { 65 if(hooks == null) 66 throw new IllegalStateException("Shutdown in progress"); 67 68 if (hook.isAlive()) 69 throw new IllegalArgumentException("Hook already running"); 70 71 if (hooks.containsKey(hook)) 72 throw new IllegalArgumentException("Hook previously registered"); 73 74 hooks.put(hook, hook); 75 } 76 77 /* Remove a previously-registered hook. Like the add method, this method 78 * does not do any security checks. 79 */ remove(Thread hook)80 static synchronized boolean remove(Thread hook) { 81 if(hooks == null) 82 throw new IllegalStateException("Shutdown in progress"); 83 84 if (hook == null) 85 throw new NullPointerException(); 86 87 return hooks.remove(hook) != null; 88 } 89 90 /* Iterates over all application hooks creating a new thread for each 91 * to run in. Hooks are run concurrently and this method waits for 92 * them to finish. 93 */ runHooks()94 static void runHooks() { 95 Collection<Thread> threads; 96 synchronized(ApplicationShutdownHooks.class) { 97 threads = hooks.keySet(); 98 hooks = null; 99 } 100 101 for (Thread hook : threads) { 102 hook.start(); 103 } 104 for (Thread hook : threads) { 105 try { 106 hook.join(); 107 } catch (InterruptedException x) { } 108 } 109 } 110 } 111