org.jboss.ejb.plugins.lock
Class QueuedPessimisticEJBLock

java.lang.Object
  |
  +--org.jboss.ejb.plugins.lock.BeanLockSupport
        |
        +--org.jboss.ejb.plugins.lock.QueuedPessimisticEJBLock

All Implemented Interfaces:

BeanLock

Direct Known Subclasses:

MethodOnlyEJBLock

public class QueuedPessimisticEJBLock

extends BeanLockSupport

This class is holds threads awaiting the transactional lock to be free in a fair FIFO transactional queue. Non-transactional threads are also put in this wait queue as well. Unlike SimplePessimisticEJBLock which notifies all threads on transaction completion, this class pops the next waiting transaction from the queue and notifies only those threads waiting associated with that transaction. This class should perform better than Simple on high contention loads. Holds all locks for entity beans, not used for stateful.

All BeanLocks have a reference count. When the reference count goes to 0, the lock is released from the id -> lock mapping.

Version:

$Revision: 1.3.4.3 $

Revisions:

2001/08/03: billb

1. Initial revision

Author:

Marc Fleury, Bill Burke

Fields inherited from class org.jboss.ejb.plugins.lock.BeanLockSupport

id, numMethodLocks, reentrant, refs, synched, tx, txTimeout

Constructor Summary

QueuedPessimisticEJBLock()

Method Summary

protected boolean	attemptMethodLock(MethodInvocation mi, boolean trace) Attempt to acquire a method lock.
protected boolean	doSchedule(MethodInvocation mi) doSchedule(MethodInvocation) doSchedule implements a particular policy for scheduling the threads coming in.
void	endTransaction(javax.transaction.Transaction transaction)
protected org.jboss.ejb.plugins.lock.QueuedPessimisticEJBLock.TxLock	getTxLock(javax.transaction.Transaction miTx)
protected boolean	isTxExpired(javax.transaction.Transaction miTx)
protected void	nextTransaction()
void	releaseMethodLock() releaseMethodLock if we reach the count of zero it means the instance is free from threads (and reentrency) we wake up the next thread in the currentLock
void	removeRef()
void	schedule(MethodInvocation mi)
protected boolean	waitForTx(javax.transaction.Transaction miTx, boolean trace) Wait until no other transaction is running with this lock.
void	wontSynchronize(javax.transaction.Transaction trasaction)

Methods inherited from class org.jboss.ejb.plugins.lock.BeanLockSupport

addMethodLock, addRef, getId, getNumMethodLocks, getRefs, getTransaction, isCallAllowed, isMethodLocked, releaseSync, setId, setReentrant, setTimeout, setTransaction, sync

Methods inherited from class java.lang.Object

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

Constructor Detail

QueuedPessimisticEJBLock

public QueuedPessimisticEJBLock()

Method Detail

getTxLock

protected org.jboss.ejb.plugins.lock.QueuedPessimisticEJBLock.TxLock getTxLock(javax.transaction.Transaction miTx)

isTxExpired

protected boolean isTxExpired(javax.transaction.Transaction miTx)
                       throws java.lang.Exception

schedule

public void schedule(MethodInvocation mi)
              throws java.lang.Exception

Overrides:

schedule in class BeanLockSupport

doSchedule

protected boolean doSchedule(MethodInvocation mi)
                      throws java.lang.Exception

doSchedule(MethodInvocation) doSchedule implements a particular policy for scheduling the threads coming in. There is always the spec required "serialization" but we can add custom scheduling in here Synchronizing on lock: a failure to get scheduled must result in a wait() call and a release of the lock. Schedulation must return with lock.

waitForTx

protected boolean waitForTx(javax.transaction.Transaction miTx,
                            boolean trace)
                     throws java.lang.Exception

Wait until no other transaction is running with this lock.

Returns:

Returns true if this thread was scheduled in txWaitQueue

attemptMethodLock

protected boolean attemptMethodLock(MethodInvocation mi,
                                    boolean trace)
                             throws java.lang.Exception

Attempt to acquire a method lock.

nextTransaction

protected void nextTransaction()

endTransaction

public void endTransaction(javax.transaction.Transaction transaction)

Overrides:

endTransaction in class BeanLockSupport

wontSynchronize

public void wontSynchronize(javax.transaction.Transaction trasaction)

Overrides:

wontSynchronize in class BeanLockSupport

releaseMethodLock

public void releaseMethodLock()

releaseMethodLock if we reach the count of zero it means the instance is free from threads (and reentrency) we wake up the next thread in the currentLock

Overrides:

releaseMethodLock in class BeanLockSupport

removeRef

public void removeRef()

Overrides:

removeRef in class BeanLockSupport