org.axonframework.common.lock

Class PessimisticLockFactory

java.lang.Object

org.axonframework.common.lock.PessimisticLockFactory

All Implemented Interfaces:

LockFactory

public class PessimisticLockFactory
extends Object
implements LockFactory

Implementation of a LockFactory that uses a pessimistic locking strategy. Calls to obtainLock(java.lang.String) will block until a lock could be obtained or back off limit is reached, based on the PessimisticLockFactory.BackoffParameters, by throwing an exception. The latter will cause the command to fail, but will allow the calling thread to be freed. If a lock is obtained by a thread, that thread has guaranteed unique access.

Each thread can hold the same lock multiple times. The lock will only be released for other threads when the lock has been released as many times as it was obtained.

This lock can be used to ensure thread safe access to a number of objects, such as Aggregates and Sagas.

Back off properties with respect to acquiring locks can be configured through the PessimisticLockFactory.BackoffParameters.

Since:

1.3

Author:

Allard Buijze, Michael Bischoff

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	PessimisticLockFactory.BackoffParameters There are 3 values:

Constructor Summary

Constructors

Constructor and Description
PessimisticLockFactory() Deprecated.
PessimisticLockFactory(PessimisticLockFactory.BackoffParameters backoffParameters) Creates a new IdentifierBasedLock instance.

Method Summary

Modifier and Type	Method and Description
Lock	obtainLock(String identifier) Obtain a lock for a resource identified by the given identifier.

Methods inherited from class java.lang.Object

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

Constructor Detail

PessimisticLockFactory

@Deprecated
public PessimisticLockFactory()

Deprecated.

Creates a new IdentifierBasedLock instance.

Deadlocks are detected across instances of the IdentifierBasedLock. This constructor specifies no back off from lock acquisition

PessimisticLockFactory

public PessimisticLockFactory(PessimisticLockFactory.BackoffParameters backoffParameters)

Creates a new IdentifierBasedLock instance.

Deadlocks are detected across instances of the IdentifierBasedLock. Back off policy as by supplied PessimisticLockFactory.BackoffParameters

Parameters:

backoffParameters - back off policy configuration

Method Detail

obtainLock

public Lock obtainLock(String identifier)

Obtain a lock for a resource identified by the given identifier. This method will block until a lock was successfully obtained.

Note: when an exception occurs during the locking process, the lock may or may not have been allocated.

Specified by:

obtainLock in interface LockFactory

Parameters:

identifier - the identifier of the lock to obtain.

Returns:

a handle to release the lock. If the thread that releases the lock does not hold the lock IllegalMonitorStateException is thrown