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JBoss API: Class SimplePessimisticEJBLock

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org.jboss.ejb.plugins.lock
Class SimplePessimisticEJBLock

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

All Implemented Interfaces:: BeanLock

public class SimplePessimisticEJBLock
extends BeanLockSupport

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: 1.5.4.3 $

Revisions:

2001/07/29: billb

Initial revision

2001/08/01: marcf

Added the schedule method
The bean lock is now responsible for implementing the locking policies, it was before in the interceptor code it is now factored out allowing for pluggable lock policies (optimistic for ex)
Implemented pessimistic locking and straight spec requirement in the schedule method would need to factor this in an abstract class for the BeanLock that extending policies can use

2001/08/02: marcf

Did what was said above, moved to an extension based mech with an abstract base class.
This is the simple lock, won't scale well (imho) but is robust in normal operation
The class must now implement schedule and the various notification calls. EndTransaction wontSynchronize can be radically different (N-Lock)

Author:

Bill Burke, Marc Fleury

Field Summary

java.lang.Object lock
          The actual lock object

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

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

Constructor Summary

SimplePessimisticEJBLock()


Method Summary

protected boolean doSchedule(MethodInvocation mi)
          doSchedule implements a particular policy for scheduling the threads coming in.

void endTransaction(javax.transaction.Transaction transaction)
          This is called up synchronization to notify the end of the transaction.

java.lang.Object getLock()


void 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 schedule(MethodInvocation mi)


void wontSynchronize(javax.transaction.Transaction transaction)
          This is called if the synchronization missed registration (Sync interceptor).

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

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

Methods inherited from class java.lang.Object

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

Field Detail

lock

public java.lang.Object lock

The actual lock object

Constructor Detail

SimplePessimisticEJBLock

public SimplePessimisticEJBLock()

Method Detail

getLock

public java.lang.Object getLock()

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 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.

Returns:: Returns true if the thread is scheduled to go through the rest of the interceptors. Returns false if the interceptor must try the scheduling again.

wontSynchronize

public void wontSynchronize(javax.transaction.Transaction transaction)

This is called if the synchronization missed registration (Sync interceptor).

Overrides:: wontSynchronize in class BeanLockSupport

endTransaction

public void endTransaction(javax.transaction.Transaction transaction)

This is called up synchronization to notify the end of the transaction.

Overrides:: endTransaction in class BeanLockSupport

releaseMethodLock

public void 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