org.objectweb.cjdbc.controller.scheduler.schema
Class TransactionExclusiveLock

java.lang.Object
  org.objectweb.cjdbc.controller.scheduler.schema.TransactionExclusiveLock

public class TransactionExclusiveLock

extends java.lang.Object

A TransactionExclusiveLock is an exclusive lock that let the owner of the lock acquire several times the lock (but it needs to be released only once). Acquire supports timeout and graceful withdrawal of timed out requests.

Version:

1.0

Author:

Emmanuel Cecchet

Nested Class Summary

private class

TransactionExclusiveLock.WaitingListElement The element stored in the waiting list is the waiting thread and the transaction id of the request waiting.

Field Summary

private boolean	isLocked
private long	locker Transaction id of the lock holder.
private java.util.ArrayList	waitingList ArrayList of WaitingListElement.

Constructor Summary

TransactionExclusiveLock()

Method Summary

boolean	acquire(AbstractRequest request) Acquires an exclusive lock on this table.
long	getLocker() Returns the transaction id of the lock owner.
java.util.ArrayList	getWaitingList() Returns the waitingList.
boolean	isLocked() Returns true if the lock is owned by someone.
boolean	isWaiting(long transactionId) Returns true if the given transaction id is contained in this lock waiting queue.
void	release() Releases the lock on this table.

Methods inherited from class java.lang.Object

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

Field Detail

isLocked

private boolean isLocked

locker

private long locker

Transaction id of the lock holder.

waitingList

private java.util.ArrayList waitingList

ArrayList of WaitingListElement.

Constructor Detail

TransactionExclusiveLock

public TransactionExclusiveLock()

Method Detail

acquire

public boolean acquire(AbstractRequest request)

Acquires an exclusive lock on this table. If the lock is already held by the same transaction as the given request, this method is non-blocking else the caller is blocked until the transaction holding the lock releases it at commit/rollback time.

Parameters:

request - request asking for the lock (timeout field is used and updated upon waiting)

Returns:

boolean true is the lock has been successfully acquired, false on timeout or error

See Also:

release()

release

public void release()

Releases the lock on this table.

See Also:

acquire(AbstractRequest)

isLocked

public boolean isLocked()

Returns true if the lock is owned by someone.

Returns:

boolean value

getLocker

public long getLocker()

Returns the transaction id of the lock owner. The return value is undefined if the lock is not owned (usually it is the last owner).

Returns:

int the transaction id.

getWaitingList

public java.util.ArrayList getWaitingList()

Returns the waitingList.

Returns:

an ArrayList of WaitingListElement

isWaiting

public boolean isWaiting(long transactionId)

Returns true if the given transaction id is contained in this lock waiting queue.

Parameters:

transactionId - a transaction id

Returns:

a boolean value