001/*
002 * Copyright 2010-2015 Institut Pasteur.
003 * 
004 * This file is part of Icy.
005 * 
006 * Icy is free software: you can redistribute it and/or modify
007 * it under the terms of the GNU General Public License as published by
008 * the Free Software Foundation, either version 3 of the License, or
009 * (at your option) any later version.
010 * 
011 * Icy is distributed in the hope that it will be useful,
012 * but WITHOUT ANY WARRANTY; without even the implied warranty of
013 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
014 * GNU General Public License for more details.
015 * 
016 * You should have received a copy of the GNU General Public License
017 * along with Icy. If not, see <http://www.gnu.org/licenses/>.
018 */
019package icy.system;
020
021import icy.file.FileUtil;
022
023import java.io.File;
024import java.io.FileOutputStream;
025import java.io.IOException;
026import java.nio.channels.FileLock;
027
028/**
029 * Class to verify we have a single instance of an object or whatever (use {@link FileLock}).
030 * 
031 * @author Stephane
032 */
033public class SingleInstanceCheck
034{
035    public static FileLock lock(String id)
036    {
037        FileLock result;
038        final File f = new File(FileUtil.getTempDirectory() + FileUtil.separator + id + ".lock");
039
040        try
041        {
042            result = new FileOutputStream(f).getChannel().tryLock();
043        }
044        catch (Exception e)
045        {
046            result = null;
047        }
048
049        return result;
050    }
051
052    public static boolean release(FileLock lock)
053    {
054        if (lock != null)
055        {
056            try
057            {
058                lock.release();
059                return true;
060            }
061            catch (IOException e)
062            {
063                // ignore
064            }
065        }
066
067        return false;
068    }
069}