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/* |
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* This is free software; you can redistribute it and/or modify it |
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* under the terms of the GNU Lesser General Public License as |
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* published by the Free Software Foundation; either version 2.1 of |
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* the License, or (at your option) any later version. |
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* |
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* This software is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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* Lesser General Public License for more details. |
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*/ |
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package com.strider.datadefender.utils; |
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import java.io.File; |
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import java.io.FileNotFoundException; |
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import java.io.IOException; |
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import java.io.RandomAccessFile; |
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import java.nio.channels.FileChannel; |
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import java.nio.channels.FileLock; |
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import java.nio.channels.OverlappingFileLockException; |
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import com.strider.datadefender.DataDefenderException; |
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import lombok.extern.log4j.Log4j2; |
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/** |
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* Most of the code is copied from this page: http://www.rgagnon.com/javadetails/java-0288.html |
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* |
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* Modified by Armenak Grigoryan |
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*/ |
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@Log4j2 |
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public class ApplicationLock { |
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private final String appName; |
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private File file; |
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private FileChannel channel; |
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private FileLock lock; |
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/** |
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* Constructor |
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* |
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* @param appName application name |
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*/ |
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public ApplicationLock(final String appName) { |
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this.appName = appName; |
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} |
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private void closeLock() throws DataDefenderException { |
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try { |
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lock.release(); |
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} catch (IOException e) { |
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throw new DataDefenderException("Problem releasing file lock", e); |
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} |
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try { |
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channel.close(); |
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} catch (IOException e) { |
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throw new DataDefenderException("Problem closing channel", e); |
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} |
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} |
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private void deleteFile() { |
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file.delete(); |
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} |
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/** |
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* Returns true if there is another instance of the application is running. |
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* Otherwise returns false. |
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* |
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* @return boolean |
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* @throws com.strider.datadefender.DataDefenderException |
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*/ |
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public boolean isAppActive() throws DataDefenderException { |
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try { |
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file = new File(System.getProperty("user.home"), appName + ".tmp"); |
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channel = new RandomAccessFile(file, "rw").getChannel(); |
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log.debug("Creating lock file " + file.getName()); |
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try { |
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lock = channel.tryLock(); |
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log.debug("Locking file ..."); |
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} catch (OverlappingFileLockException | IOException e) { |
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// already locked |
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log.error("File " + file.getName() + " already locket"); |
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closeLock(); |
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return true; |
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} |
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if (lock == null) { |
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closeLock(); |
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return true; |
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} |
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Runtime.getRuntime().addShutdownHook(new Thread() { |
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// destroy the lock when the JVM is closing |
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@Override |
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public void run() { |
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try { |
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log.debug("Closing lock file"); |
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closeLock(); |
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deleteFile(); |
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} catch (DataDefenderException ae) { |
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log.error("Problem closing file lock"); |
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} |
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} |
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}); |
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return false; |
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} catch (FileNotFoundException fnfe) { |
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closeLock(); |
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return true; |
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} |
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} |
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} |
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//~ Formatted by Jindent --- http://www.jindent.com |
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|
armenak /
DataDefender
