org.apache.commons.transaction.locking
Class ReadWriteUpgradeLockManager

java.lang.Object
  org.apache.commons.transaction.locking.GenericLockManager
      org.apache.commons.transaction.locking.ReadWriteLockManager
          org.apache.commons.transaction.locking.ReadWriteUpgradeLockManager

All Implemented Interfaces:

LockManager, LockManager2

public class ReadWriteUpgradeLockManager

extends ReadWriteLockManager

Manager for ReadWriteUpgradeLocks on resources.

The idea (as explained by Jim LoVerde) is that only one owner can hold an upgrade lock, but while that is held, it is possible for read locks to exist and/or be obtained, and when the request is made to upgrade to a write lock by the same owner, the lock manager prevents additional read locks until the write lock can be aquired.

In this sense the write lock becomes preferred over all other locks when it gets upgraded from a upgrate lock. Preferred means that if it has to wait and others wait as well it will be served before all other none preferred locking requests.

Since:

1.1

Version:

$Revision$

See Also:

ReadWriteUpgradeLock

Field Summary

Fields inherited from class org.apache.commons.transaction.locking.GenericLockManager

checkThreshhold, DEFAULT_CHECK_THRESHHOLD, DEFAULT_TIMEOUT, effectiveGlobalTimeouts, globalLocks, globalOwners, globalTimeoutMSecs, logger, maxLockLevel, timedOutOwners

Constructor Summary

ReadWriteUpgradeLockManager(LoggerFacade logger, long timeoutMSecs)
Creates a new read/write/upgrade lock manager.

Method Summary

protected GenericLock	createLock(Object resourceId)
boolean	tryUpgradeLock(Object ownerId, Object resourceId) Tries to acquire a reentrant upgrade lock on a resource.
boolean	tryWriteLock(Object ownerId, Object resourceId) Tries to acquire an exclusive, reentrant write lock on a resource.
void	upgradeLock(Object ownerId, Object resourceId) Tries to acquire a reentrant upgrade lock on a resource.
void	writeLock(Object ownerId, Object resourceId) Tries to acquire an exclusive, reentrant write lock on a resource.

Methods inherited from class org.apache.commons.transaction.locking.ReadWriteLockManager

checkReadLock, checkWriteLock, hasReadLock, hasWriteLock, readLock, tryReadLock

Methods inherited from class org.apache.commons.transaction.locking.GenericLockManager

addOwner, atomicGetOrCreateLock, checkLock, doLock, getAll, getLevel, getLock, getLocks, getNextGlobalConflictTimeout, hasLock, lock, lock, lock, release, releaseAll, releaseAllNoTimeOutReset, releaseTimedOutOwners, removeLock, removeOwner, startGlobalTimeout, timeOut, timeoutCheck, toString, tryLock, wouldDeadlock

Methods inherited from class java.lang.Object

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

Constructor Detail

ReadWriteUpgradeLockManager

public ReadWriteUpgradeLockManager(LoggerFacade logger,
                                   long timeoutMSecs)

Creates a new read/write/upgrade lock manager.

Parameters:

logger - generic logger used for all kind of debug logging

timeoutMSecs - specifies the maximum time to wait for a lock in milliseconds

Method Detail

tryUpgradeLock

public boolean tryUpgradeLock(Object ownerId,
                              Object resourceId)

Tries to acquire a reentrant upgrade lock on a resource.

This method does not block, but immediatly returns. If a lock is not available false will be returned.

Parameters:

ownerId - a unique id identifying the entity that wants to acquire this lock

resourceId - the resource to get the lock for

Returns:

true if the lock has been acquired, false otherwise

tryWriteLock

public boolean tryWriteLock(Object ownerId,
                            Object resourceId)

Tries to acquire an exclusive, reentrant write lock on a resource.

This method does not block, but immediatly returns. If a lock is not available false will be returned.

Overrides:

tryWriteLock in class ReadWriteLockManager

Parameters:

ownerId - a unique id identifying the entity that wants to acquire this lock

resourceId - the resource to get the lock for

Returns:

true if the lock has been acquired, false otherwise

upgradeLock

public void upgradeLock(Object ownerId,
                        Object resourceId)
                 throws LockException

Tries to acquire a reentrant upgrade lock on a resource.

This method blocks and waits for the lock in case it is not avaiable. If there is a timeout or a deadlock or the thread is interrupted a LockException is thrown.

Parameters:

ownerId - a unique id identifying the entity that wants to acquire this lock

resourceId - the resource to get the level for

Throws:

LockException - will be thrown when the lock can not be acquired

writeLock

public void writeLock(Object ownerId,
                      Object resourceId)
               throws LockException

Tries to acquire an exclusive, reentrant write lock on a resource.

This method blocks and waits for the lock in case it is not avaiable. If there is a timeout or a deadlock or the thread is interrupted a LockException is thrown.

Overrides:

writeLock in class ReadWriteLockManager

Parameters:

ownerId - a unique id identifying the entity that wants to acquire this lock

resourceId - the resource to get the level for

Throws:

LockException - will be thrown when the lock can not be acquired

createLock

protected GenericLock createLock(Object resourceId)

Overrides:

createLock in class ReadWriteLockManager