org.sourceforge.jemm.util
Class LockManager<K>

java.lang.Object
  org.sourceforge.jemm.util.LockManager<K>

Type Parameters:

K - The type of ID to use as the lock key

public class LockManager<K>
extends java.lang.Object

A generic mutual exclusion lock manager for locks on arbitrary ids. From the callers point of view the lock always exists. Internally this lock may be created on the fly as needed. If two clients attempt to acquire the same lock one will end up holding the lock and one will be blocked until the lock is freed by the first. From an administration point of view, old, unused locks may be reclaimed using the clearUnusedLocks() method. Note synchronisation blocks are not needed, as per Java 6 Semaphore javadoc comment: 'Memory consistency effects: Actions in a thread prior to calling a "release" method such as release() happen-before actions following a successful "acquire" method such as acquire() in another thread. '

Author:

Rory Graves

Field Summary

static long	ERROR_TIMEOUT
protected org.sourceforge.jemm.util.LockManager.LockStore	lockStore

Constructor Summary

LockManager()

Method Summary

void	acquire(K lockId) Acquire the lock on lock 'lockId', if necessary blocking until the lock becomes available.
java.lang.Thread	getLockHolder(K id)
int	noLocksHeld()
void	release(K lockId) Release the lock on 'lockId'

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

ERROR_TIMEOUT

public static final long ERROR_TIMEOUT

See Also:

Constant Field Values

lockStore

protected org.sourceforge.jemm.util.LockManager.LockStore lockStore

Constructor Detail

LockManager

public LockManager()

Method Detail

acquire

public void acquire(K lockId)

Acquire the lock on lock 'lockId', if necessary blocking until the lock becomes available.

Parameters:

lockId - The id of the lock to acquire

Throws:

java.lang.InterruptedException

release

public void release(K lockId)

Release the lock on 'lockId'

Parameters:

lockId - The lockId of the lock to release.

noLocksHeld

public int noLocksHeld()

getLockHolder

public java.lang.Thread getLockHolder(K id)