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IdentityLock (JBossCache API) - JBoss 4.0.1 sp1 Cache API Documentation 英文版文档

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org.jboss.cache.lock
Class IdentityLock

java.lang.Object
  org.jboss.cache.lock.IdentityLock

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public class IdentityLock

extends Object

Lock object which grants and releases locks, and associates locks with owners. The methods to acquire and release a lock require an owner (Object). When a lock is acquired, we store the current owner with the lock. When the same owner (but possibly running in a different thread) wants to acquire the lock, it is immediately granted. When an owner different from the one currently owning the lock wants to release the lock, we do nothing (no-op).

Consider the following example:

 FIFOSemaphore lock=new FIFOSemaphore(1);
 lock.acquire();
 lock.acquire();
 lock.release();
 

This would block on the second acquire() (although we currently already hold the lock) because the lock only has 1 permit. So IdentityLock will allow the following code to work properly:

 IdentityLock lock=new IdentityLock();
 lock.readLock().acquire(this, timeout);
 lock.writeLock().acquire(this, timeout);
 lock.release(this);
 

If the owner is null, then the current thread is taken by default. This allow the following code to work:

 IdentityLock lock=new IdentityLock();
 lock.readLock().attempt(null, timeout);
 lock.writeLock().attempt(null, timeout);
 lock.release(null);
 

Note that the Object given as owner is required to implement Object.equals(java.lang.Object). For a use case see the examples in the testsuite.

Version:

$Revision: 1.13.2.1 $

Author:

Bela Ban Apr 11, 2003, Ben Wang July 2003

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Constructor Summary

IdentityLock(TreeCache cache, Fqn fqn)

 

Method Summary
boolean	acquireReadLock(Object owner, long timeout)           Acquire a read lock with a timeout period of timeout milliseconds.
boolean	acquireWriteLock(Object owner, long timeout)           Acquire a write lock with a timeout of timeout milliseconds.
Fqn	getFqn()
List	getReaderOwners()           Return a copy of the reader lock owner in List.
Object	getWriterOwner()           Return the writer lock owner object.
boolean	isLocked()           Check if there is a read or write lock
boolean	isOwner(Object o)           Am I a lock owner?
boolean	isReadLocked()           Check if there is a read lock.
boolean	isWriteLocked()           Check if there is a write lock.
void	release(Object owner)           Release the lock held by the owner.
void	releaseAll()           Release all locks associated with this instance.
void	releaseForce()           Same as releaseAll now.
String	toString()
void	toString(StringBuffer sb)

 

Methods inherited from class java.lang.Object

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

 

Constructor Detail

IdentityLock

public IdentityLock(TreeCache cache,
                    Fqn fqn)

Method Detail

getFqn

public Fqn getFqn()

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getReaderOwners

public List getReaderOwners()

Return a copy of the reader lock owner in List. Size is zero is not available. Note that this list is synchronized.

Returns:

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getWriterOwner

public Object getWriterOwner()

Return the writer lock owner object. Null if not available.

Returns:

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acquireWriteLock

public boolean acquireWriteLock(Object owner,
                                long timeout)
                         throws LockingException,
                                TimeoutException

Acquire a write lock with a timeout of timeout milliseconds. Note that if the current owner owns a read lock, it will be upgraded automatically. However, if upgrade fails, i.e., timeout, the read lock will be released automatically.

Parameters:

owner - Can't be null.

timeout -

Returns:

boolean True if lock was acquired and was not held before, false if lock was held

Throws:

LockingException

TimeoutException

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acquireReadLock

public boolean acquireReadLock(Object owner,
                               long timeout)
                        throws LockingException,
                               TimeoutException

Acquire a read lock with a timeout period of timeout milliseconds.

Parameters:

owner - Can't be null.

timeout -

Returns:

boolean True if lock was acquired and was not held before, false if lock was held

Throws:

LockingException

TimeoutException

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release

public void release(Object owner)

Release the lock held by the owner.

Parameters:

owner - Can't be null.

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releaseAll

public void releaseAll()

Release all locks associated with this instance.

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releaseForce

public void releaseForce()

Same as releaseAll now.

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isReadLocked

public boolean isReadLocked()

Check if there is a read lock.

Returns:

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isWriteLocked

public boolean isWriteLocked()

Check if there is a write lock.

Returns:

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isLocked

public boolean isLocked()

Check if there is a read or write lock

Returns:

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isOwner

public boolean isOwner(Object o)

Am I a lock owner?

Parameters:

o -

Returns:

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toString

public String toString()

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toString

public void toString(StringBuffer sb)

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