org.sourceforge.jemm.client
Class SynchronousLockDecorator

java.lang.Object
  org.sourceforge.jemm.client.DelegatingObjectDatabase
      org.sourceforge.jemm.client.SynchronousLockDecorator

All Implemented Interfaces:

ObjectDatabase, ObjectSource, TypeRequestHandler, LockAcquiredListener

public class SynchronousLockDecorator
extends DelegatingObjectDatabase
implements LockAcquiredListener

An ObjectDatabase implementation that converts acquireLock calls into synchronous calls that wait for the lock to be acquired. Implementation notes -------------------- This implementation works by each thread registering itself in a Map with its clientThreadId pointing to a lock object on which the thread waits. Once the async listener calls for that particular ID then the lock is notified and the original thread is released. Since a clientThreadId is unique for each thread there is only ever one listener per lock. Note that if the clientThreadId is not unique by thread then acquireLock will return without acquiring the lock and threads could be locked indefinitely.

Author:

Paul Keeble

Constructor Summary

SynchronousLockDecorator(ClientId clientId, ObjectDatabase delegate)

Method Summary

void	acquireLock(ClientThreadId threadId, ID jemmId) Acquires a lock by calling onto the delegate database and waiting for an asynchronous response back.
void	lockAcquired(ClientThreadId threadId, ID object) A listener method implementation that gets the lock and notifies the waiting thread.
void	removeLockAcquiredListener(ClientId clientId) Attempts to change the LockAcquiredListener are ignored.
void	setClientLockAcquiredListener(ClientId clientId, LockAcquiredListener listener) Attempts to change the LockAcquiredListener are ignored.

Methods inherited from class org.sourceforge.jemm.client.DelegatingObjectDatabase

getClassInfo, getEnumInfo, getObject, getRefreshedObject, getRoot, newObject, processTypeRequest, refreshObject, registerClass, registerEnum, releaseLock, setRoot, setRootIfNull, synchroniseObject

Methods inherited from class java.lang.Object

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

Constructor Detail

SynchronousLockDecorator

public SynchronousLockDecorator(ClientId clientId,
                                ObjectDatabase delegate)

Method Detail

acquireLock

public void acquireLock(ClientThreadId threadId,
                        ID jemmId)

Acquires a lock by calling onto the delegate database and waiting for an asynchronous response back. Blocks until a response of some description is returned.

Specified by:

acquireLock in interface ObjectDatabase

Overrides:

acquireLock in class DelegatingObjectDatabase

Parameters:

threadId - a unique identifier for a Thread (and client). MUST BE UNIQUE PER THREAD.

jemmId - The ID to lock on

removeLockAcquiredListener

public void removeLockAcquiredListener(ClientId clientId)

Attempts to change the LockAcquiredListener are ignored.

Specified by:

removeLockAcquiredListener in interface ObjectDatabase

Overrides:

removeLockAcquiredListener in class DelegatingObjectDatabase

Parameters:

clientId - The id the the client who is no longer interested in lock events.

setClientLockAcquiredListener

public void setClientLockAcquiredListener(ClientId clientId,
                                          LockAcquiredListener listener)

Attempts to change the LockAcquiredListener are ignored.

Specified by:

setClientLockAcquiredListener in interface ObjectDatabase

Overrides:

setClientLockAcquiredListener in class DelegatingObjectDatabase

Parameters:

clientId - The client who is interested in their lock event notifications.

listener - The listener to register.

lockAcquired

public void lockAcquired(ClientThreadId threadId,
                         ID object)

A listener method implementation that gets the lock and notifies the waiting thread.

Specified by:

lockAcquired in interface LockAcquiredListener