com.fusesource.forge.jmstest.threading.ReleaseManager.java Source code

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Here is the source code for com.fusesource.forge.jmstest.threading.ReleaseManager.java

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/*
 * Copyright (C) 2009, Progress Software Corporation and/or its
 * subsidiaries or affiliates.  All rights reserved.
 *
 * Licensed 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 com.fusesource.forge.jmstest.threading;

import java.util.Vector;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * This class is a utility class where resources with cleanup requirements can be registered.
 * An instance of this class needs to be registered as a shutdown hook within the JVM. Each
 * registered object must implement the <code>Releasable</code> interface. Once the
 * shutdown hook is triggered, the <code>release()</code> method of all releasables
 * will be executed.
 *
 * @author Andreas Gies
 * @see Releaseable
 */
public class ReleaseManager extends Thread {

    private transient Log log;
    private Vector<Releaseable> releaseables;
    private static ReleaseManager instance = null;

    synchronized static public ReleaseManager getInstance() {
        if (instance == null) {
            instance = new ReleaseManager();
            Runtime.getRuntime().addShutdownHook(instance);
        }
        return instance;
    }

    private ReleaseManager() {
        releaseables = new Vector<Releaseable>();
    }

    public void register(Releaseable releaseable) {
        synchronized (releaseables) {
            releaseables.add(releaseable);
        }
    }

    public void deregister(Releaseable releaseable) {
        synchronized (releaseable) {
            releaseables.remove(releaseable);
        }
    }

    @Override
    public void run() {
        log().info("ShutdownHook called, attempting to sweep up resources");

        synchronized (releaseables) {
            while (releaseables != null && releaseables.size() > 0) {
                Releaseable r = releaseables.remove(0);
                r.release();
            }
        }
    }

    protected Log log() {
        if (log == null) {
            log = LogFactory.getLog(getClass());
        }
        return log;
    }

    static {
        ReleaseManager.getInstance();
    }
}