Java shutdown hook is not guaranteed to execute. - Java java.lang

Java examples for java.lang:Thread

  1. HOME
  2. Java
  3. java.lang
  4. Thread

Description

Java shutdown hook is not guaranteed to execute.

Demo Code

/*/*from   w  ww. ja va  2 s.com*/
 * Copyright 2013 Simon Thiel
 *
 * This file is part of SitJar.
 *
 * SitJar is free software: you can redistribute it and/or modify
 * it under the terms of the GNU LESSER GENERAL PUBLIC LICENSE as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * SitJar is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with SitJar. If not, see <http://www.gnu.org/licenses/lgpl.txt>.
 */
import java.util.logging.Level;
import java.util.logging.Logger;

public class Main{
    /**
     * http://www.certpal.com/blogs/2009/08/java-shutdown-hooks/
     *
     * shutdown hook is not guaranteed to execute. If a user closes the app abruptly or the
     * VM crashes, or you click on the little red button on the eclipse console view, the shutdown
     * hook will not run. It is not a good idea to use a shutdown hook to release critical resources
     * (I have seen some code snippets that do this). It might end up not running and cause damage.
     * The shutdown hook will execute only on normal termination or orderly shutdown.
     *
     * Use the shutdown hook if you would like to do trivial operations with it. You can write code i
     * nside the hook that can clean up after the program (say delete a temporary file). Or write a bye
     * bye message. The code inside the hook should not do critical things like release DB connections
     * that your program acquired. Doing something like that is asking for trouble, since this code may
     * never run.
     *
     * Also keep in mind that hooks run concurrently. Each hook is registered as a Thread with the VM and each
     * Thread will run in parallel with the other hooks. If the hooks synchronize over resources incorrectly
     * you will end up dead locking the application.
     *
     * The hooks also need to finish up quickly. If they do not, that poses a
     * problem. The application will wait for ever to exit gracefully.
     *
     *
     * @param delgation
     */
    public static void registerShutdownHook(
            final ShutdownHookDelegation delgation) {
        Runtime runtime = Runtime.getRuntime();
        Thread shutdownThread = new Thread(new Runnable() {

            private final ShutdownHookDelegation myDelegation = delgation;

            public void run() {
                myDelegation.executeOnShutdown();
            }
        });
        runtime.addShutdownHook(shutdownThread);
    }
}

Related Tutorials