jdk/src/share/classes/java/lang/ApplicationShutdownHooks.java
author smarks
Mon, 20 Dec 2010 13:47:04 -0800
changeset 7803 56bc97d69d93
parent 5506 202f599c92aa
child 9035 1255eb81cc2f
permissions -rw-r--r--
6880112: Project Coin: Port JDK core library code to use diamond operator Reviewed-by: darcy, lancea, alanb, briangoetz, mduigou, mchung
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/*
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 * Copyright (c) 2005, 2006, Oracle and/or its affiliates. All rights reserved.
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 *
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 * This code is free software; you can redistribute it and/or modify it
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 * under the terms of the GNU General Public License version 2 only, as
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 * published by the Free Software Foundation.  Oracle designates this
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 * particular file as subject to the "Classpath" exception as provided
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 * by Oracle in the LICENSE file that accompanied this code.
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 *
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 * This code is distributed in the hope that it will be useful, but WITHOUT
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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 * version 2 for more details (a copy is included in the LICENSE file that
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 * accompanied this code).
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 *
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 * You should have received a copy of the GNU General Public License version
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 * 2 along with this work; if not, write to the Free Software Foundation,
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 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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 *
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 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 * or visit www.oracle.com if you need additional information or have any
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 * questions.
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 */
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package java.lang;
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import java.util.*;
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/*
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 * Class to track and run user level shutdown hooks registered through
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 * <tt>{@link Runtime#addShutdownHook Runtime.addShutdownHook}</tt>.
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 *
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 * @see java.lang.Runtime#addShutdownHook
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 * @see java.lang.Runtime#removeShutdownHook
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 */
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class ApplicationShutdownHooks {
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    /* The set of registered hooks */
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    private static IdentityHashMap<Thread, Thread> hooks;
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    static {
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        try {
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            Shutdown.add(1 /* shutdown hook invocation order */,
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                false /* not registered if shutdown in progress */,
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                new Runnable() {
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                    public void run() {
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                        runHooks();
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                    }
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                }
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            );
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            hooks = new IdentityHashMap<>();
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        } catch (IllegalStateException e) {
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            // application shutdown hooks cannot be added if
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            // shutdown is in progress.
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            hooks = null;
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        }
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    }
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    private ApplicationShutdownHooks() {}
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    /* Add a new shutdown hook.  Checks the shutdown state and the hook itself,
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     * but does not do any security checks.
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     */
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    static synchronized void add(Thread hook) {
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        if(hooks == null)
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            throw new IllegalStateException("Shutdown in progress");
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        if (hook.isAlive())
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            throw new IllegalArgumentException("Hook already running");
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        if (hooks.containsKey(hook))
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            throw new IllegalArgumentException("Hook previously registered");
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        hooks.put(hook, hook);
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    }
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    /* Remove a previously-registered hook.  Like the add method, this method
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     * does not do any security checks.
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     */
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    static synchronized boolean remove(Thread hook) {
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        if(hooks == null)
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            throw new IllegalStateException("Shutdown in progress");
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        if (hook == null)
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            throw new NullPointerException();
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        return hooks.remove(hook) != null;
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    }
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    /* Iterates over all application hooks creating a new thread for each
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     * to run in. Hooks are run concurrently and this method waits for
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     * them to finish.
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     */
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    static void runHooks() {
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        Collection<Thread> threads;
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        synchronized(ApplicationShutdownHooks.class) {
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            threads = hooks.keySet();
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            hooks = null;
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        }
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        for (Thread hook : threads) {
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            hook.start();
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        }
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        for (Thread hook : threads) {
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            try {
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                hook.join();
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            } catch (InterruptedException x) { }
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        }
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    }
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}