Examples of java.nio.channels.FileChannel.tryLock()

java.nio.channels.FileChannel.tryLock()
Attempts to acquire an exclusive lock on this file without blocking.
This is a convenience method for attempting to acquire a maximum length lock on the file. It is equivalent to:
```
 fileChannel.tryLock(0L, Long.MAX_VALUE, false) 
```
The method returns null if the acquisition would result in an overlapped lock with another OS process.
@return the file lock object, or null if the lock wouldoverlap an existing exclusive lock in another OS process. @throws ClosedChannelException the file channel is closed. @throws OverlappingFileLockException Either a lock is already held that overlaps this lock request, or another thread is waiting to acquire a lock that will overlap with this request. @throws IOException if any I/O error occurs

    assertNotNull(channel.lock(0, 10, false));
    assertNotNull(channel.lock(0, 10, true));


    assertNotNull(channel.tryLock());
    assertNotNull(channel.tryLock(0, 10, false));
    assertNotNull(channel.tryLock(0, 10, true));


    FileLock lock = channel.lock();
    assertTrue(lock.isValid());
    lock.release();
    assertFalse(lock.isValid());

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        // Try acquiring the lock without blocking. This method returns
        // null or throws an exception if the file is already locked.
        while(!lock.isValid()) {
            try {
                lock = channel.tryLock();
            } catch (OverlappingFileLockException e) {
                // File is already locked in this thread or virtual machine
            }
            // wait for the other process to unlock it, should take a couple of seconds
            try {

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            {
                _storeRAF = new RandomAccessFile(_storeFile, "rw");
                FileChannel fileChannel = _storeRAF.getChannel();
                try
                {
                    _storeLock = fileChannel.tryLock();
                }
                catch (OverlappingFileLockException e)
                {
                    _storeLock = null;
                }

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            lockFile.deleteOnExit();


            @SuppressWarnings("resource")
            FileOutputStream out = new FileOutputStream(lockFile);
            FileChannel channel = out.getChannel();
            _fileLock = channel.tryLock();
        }
        catch (IOException ioe)
        {
            throw new StoreException("Cannot create the lock file " + lockFile.getName(), ioe);
        }

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         */
        lockFile = new File("/tmp", "portlock_" + port); // can't use java.io.tmpdir as it is overriden by Hadoop
        if(!lockFile.exists()) {
          lockFile.createNewFile();
          FileChannel channel = new RandomAccessFile(lockFile, "rw").getChannel();
          lock = channel.tryLock();
          if(lock != null) {
            free = true;
          }
        }
        if(!free) {

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            }
            RandomAccessFile raf = new RandomAccessFile(lockfile, "rw");
            try {
                FileChannel channel = raf.getChannel();
                try {
                    FileLock lock = channel.tryLock();
                  if (lock == null) {
                        throw new IOException("Can not lock the registry cache file " + file.getAbsolutePath() + ", ignore and retry later, maybe multi java process use the file, please config: dubbo.registry.file=xxx.properties");
                    }
                  // 保存
                    try {

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                    // We got an IOException while trying to open the file.
                    // Try the next file.
                    continue;
                }
                try {
                    FileLock fl = fc.tryLock();
                    if (fl == null) {
                        // We failed to get the lock.  Try next file.
                        continue;
                    }
                    // We got the lock OK.

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      // Try to obtain a shared lock on the file channel.
      FileLock fileLock;
      try
      {
        fileLock = channel.tryLock(0L, Long.MAX_VALUE, true);
      }
      catch (Exception e)
      {
        if (debugEnabled())
        {

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      // Try to obtain an exclusive lock on the file channel.
      FileLock fileLock;
      try
      {
        fileLock = channel.tryLock(0L, Long.MAX_VALUE, false);
      }
      catch (Exception e)
      {
        if (debugEnabled())
        {

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            }
            RandomAccessFile raf = new RandomAccessFile(lockfile, "rw");
            try {
                FileChannel channel = raf.getChannel();
                try {
                    FileLock lock = channel.tryLock();
                  if (lock == null) {
                        throw new IOException("Can not lock the registry cache file " + file.getAbsolutePath() + ", ignore and retry later, maybe multi java process use the file, please config: dubbo.registry.file=xxx.properties");
                    }
                  // 保存
                    try {

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