com.jdom.mediadownloader.FileLockApplicationLock.java Source code

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Here is the source code for com.jdom.mediadownloader.FileLockApplicationLock.java

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/** 
 *  Copyright (C) 2012  Just Do One More
 *  
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program 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 General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package com.jdom.mediadownloader;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.channels.FileLock;

import com.google.common.io.Closeables;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;;

/**
 * @author djohnson
 * 
 */
public class FileLockApplicationLock implements ApplicationLock {

    private static final Logger LOG = LoggerFactory.getLogger(FileLockApplicationLock.class);

    private final File file;

    private FileOutputStream fos;
    private FileLock fl;

    public FileLockApplicationLock(File file) {
        this.file = file;
    }

    /**
     * {@inheritDoc}
     * 
     * @see com.jdom.mediadownloader.ApplicationLock#tryLock()
     */
    @Override
    public boolean tryLock() throws LockException {
        try {
            fos = new FileOutputStream(file);
            fl = fos.getChannel().tryLock();
        } catch (IOException e) {
            throw new LockException(e);
        }

        return fl != null;
    }

    /**
     * {@inheritDoc}
     * 
     * @see com.jdom.mediadownloader.ApplicationLock#unlock()
     */
    @Override
    public void unlock() {
        if (fl != null) {
            try {
                fl.release();
            } catch (IOException ioe) {
                LOG.error("Unable to release file lock!", ioe);
            }
        }
        if (fos != null) {
            try {
                Closeables.close(fos, true);
            } catch (IOException e) {
                LOG.error("Unable to close output stream!", e);
            }
        }
    }

}