com.lowagie.rups.model.BackgroundTask Maven / Gradle / Ivy

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/*
 * $Id: BackgroundTask.java 3146 2008-02-20 18:10:07Z blowagie $
 *
 * Copyright 2007 Bruno Lowagie.
 *
 * This library 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 2.1 of the License, or (at your option) any later version.
 *
 * This library 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 this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

package com.lowagie.rups.model;

import javax.swing.SwingUtilities;

/**
 * Allows you to perform long lasting tasks in background. If we ever move to Java 6, we should use the SwingWorker
 * class (included in the JDK) instead of this custom Event Dispatching code.
 */

public abstract class BackgroundTask {

    /**
     * A wrapper for the tread that executes a time-consuming task.
     */
    private ThreadWrapper thread;

    /**
     * Starts a thread. Executes the time-consuming task in the construct method; finally calls the finish().
     */
    public BackgroundTask() {
        final Runnable doFinished = this::finished;

        Runnable doConstruct = () -> {
            try {
                doTask();
            } finally {
                thread.clear();
            }
            SwingUtilities.invokeLater(doFinished);
        };
        Thread t = new Thread(doConstruct);
        thread = new ThreadWrapper(t);
    }

    /**
     * Implement this class; the time-consuming task will go here.
     */
    public abstract void doTask();

    /**
     * Starts the thread.
     */
    public void start() {
        Thread t = thread.get();
        if (t != null) {
            t.start();
        }
    }

    /**
     * Forces the thread to stop what it's doing.
     */
    public void interrupt() {
        Thread t = thread.get();
        if (t != null) {
            t.interrupt();
        }
        thread.clear();
    }

    /**
     * Called on the event dispatching thread once the construct method has finished its task.
     */
    public void finished() {
    }

    /**
     * Inner class that holds the reference to the thread.
     */
    private static class ThreadWrapper {

        private Thread thread;

        ThreadWrapper(Thread t) {
            thread = t;
        }

        synchronized Thread get() {
            return thread;
        }

        synchronized void clear() {
            thread = null;
        }
    }
}