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e182. Creating a Shared File Lock on a File
By default, a file lock is exclusive, which means that once acquired,
no other access is permitted. A shared file lock allows other shared
locks on the file (but no exclusive locks).
Note: Some platforms do not support shared locks, in which case
the lock is automatically made into an exclusive lock. Use
FileLock.isShared() to determine the type of the lock.
try {
// Obtain a file channel
File file = new File("filename");
FileChannel channel = new RandomAccessFile(file, "rw").getChannel();
// Create a shared lock on the file.
// This method blocks until it can retrieve the lock.
FileLock lock = channel.lock(0, Long.MAX_VALUE, true);
// Try acquiring a shared lock without blocking. This method returns
// null or throws an exception if the file is already exclusively locked.
try {
lock = channel.tryLock(0, Long.MAX_VALUE, true);
} catch (OverlappingFileLockException e) {
// File is already locked in this thread or virtual machine
}
// Determine the type of the lock
boolean isShared = lock.isShared();
// Release the lock
lock.release();
// Close the file
channel.close();
} catch (Exception e) {
}
e181.
Creating a File Lock on a File
© 2002 Addison-Wesley.
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