de.aristaflow.adept2.util.locking

Class ReentrantLock.ReadLock

java.lang.Object

de.aristaflow.adept2.util.locking.ReentrantLock.Lock

de.aristaflow.adept2.util.locking.ReentrantLock.ReadLock

Enclosing class:

ReentrantLock<T>

protected class ReentrantLock.ReadLock
extends ReentrantLock.Lock

Represents a read lock which allows multiple objects to hold the lock simultaneously and multiple times but blocks as soon as one object wants a write lock.

Author:

Ulrich Kreher

Field Summary

Fields inherited from class de.aristaflow.adept2.util.locking.ReentrantLock.Lock

lockCountManager, waitersForLock

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	ReadLock(LockCountManager<? super T> lockCountManager) Creates a new read lock using the designated LockCountManager for comparing objects.

Method Summary

Modifier and Type	Method and Description
void	lock(T object, long timeout) Provides the designated object with a read lock.
protected boolean	notificationRequired() Gets whether a notification of waiting threads is required.
boolean	unlock(T object) Additionally notify the writers waiting for readers on the write lock.

Methods inherited from class de.aristaflow.adept2.util.locking.ReentrantLock.Lock

currentLockingObject, hasLock, isLocked, lock, objectsWaitingToLock

Methods inherited from class java.lang.Object

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

Constructor Detail

ReadLock

protected ReadLock(LockCountManager<? super T> lockCountManager)

Creates a new read lock using the designated LockCountManager for comparing objects.

Parameters:

lockCountManager - The manager counting locks for objects.

Method Detail

lock

public void lock(T object,
                 long timeout)
          throws java.lang.InterruptedException,
                 java.util.concurrent.TimeoutException

Provides the designated object with a read lock. The current thread will be blocked until the lock can be acquired or the timeout elapsed. Writers have priority, that is as soon as there is one object requesting a write lock, the acquisition of reading locks will be blocked.

Since the lock is reentrant, an object may acquire a lock multiple times. But it also has to release the lock per acquisition afterwards.

Overrides:

lock in class ReentrantLock.Lock

Parameters:

object - The object that requests a read lock.

timeout - The time to wait for the lock. A timeout <= 0 means to wait forever (or until the lock is granted).

Throws:

java.lang.InterruptedException - If the thread is interrupted while waiting for the lock, an InterruptedException will be thrown.

java.util.concurrent.TimeoutException - If the designated timeout elapsed before the lock can be acquired, a TimeoutException will be thrown.

unlock

public boolean unlock(T object)

Additionally notify the writers waiting for readers on the write lock.

Overrides:

unlock in class ReentrantLock.Lock

Parameters:

object - The object for which the lock should be released.

Returns:

Whether a notification is sent. This will be done only if the lock is available now and there are already other objects waiting for this lock. Otherwise (the lock remains locked by another object or it is available but there are no waiters for it) false will be returned.

notificationRequired

protected boolean notificationRequired()

Gets whether a notification of waiting threads is required. This depends on whether there are no more locks and whether there are threads waiting for the lock. This also respects writers that wait for the read lock.

Overrides:

notificationRequired in class ReentrantLock.Lock

Returns:

Whether a notification of waiting threads is required (no more locks and there are waiters for the lock).