public class ReadWriteUpgradeLock extends GenericLock
ReadWriteUpgradeLock.The idea (as explained by Jim LoVerde) on an upgrade lock is that only one owner can hold an upgrade lock, but while that is held, it is possible for read locks to exist and/or be obtained, and when the request is made to upgrade to a write lock by the same owner, the lock manager prevents additional read locks until the write lock can be aquired.
In this sense the write lock becomes preferred over all other locks when it gets upgraded from a upgrate lock. Preferred means that if it has to wait and others wait as well it will be served before all other none preferred locking requests.
Calls toacquireRead(Object, long), acquireUpgrade(Object, long) and
acquireWrite(Object, long) are blocking and reentrant. Blocking
means they will wait if they can not acquire the descired access, reentrant
means that a lock request by a specific owner will always be compatible with
other accesses on this lock by the same owner. E.g. if you already have a
lock for writing and you try to acquire write access again you will not be
blocked by this first lock, while others of course will be. This is the
natural way you already know from Java monitors and synchronized blocks.GenericLock,
ReadWriteLock,
ReadWriteUpgradeLockManagerGenericLock.LockOwner| Modifier and Type | Field and Description |
|---|---|
static int |
NO_LOCK |
static int |
READ_LOCK |
static int |
UPGRADE_LOCK |
static int |
WRITE_LOCK |
logger, owners, resourceId, waiters, waitingOwnersCOMPATIBILITY_NONE, COMPATIBILITY_REENTRANT, COMPATIBILITY_REENTRANT_AND_SUPPORT, COMPATIBILITY_SUPPORT| Constructor and Description |
|---|
ReadWriteUpgradeLock(Object resourceId,
LoggerFacade logger)
Creates a new read/write/upgrade lock.
|
| Modifier and Type | Method and Description |
|---|---|
boolean |
acquire(Object ownerId,
int targetLockLevel,
boolean wait,
int compatibility,
boolean preferred,
long timeoutMSecs)
Tries to acquire a certain lock level on this lock.
|
boolean |
acquireRead(Object ownerId,
long timeoutMSecs)
Tries to acquire a blocking, reentrant read lock.
|
boolean |
acquireUpgrade(Object ownerId,
long timeoutMSecs)
Tries to acquire a reentrant upgrade lock on a resource.
|
boolean |
acquireWrite(Object ownerId,
long timeoutMSecs)
Tries to acquire a blocking, reentrant write lock.
|
acquire, acquire, acquire, equals, getConflictingOwners, getConflictingOwners, getConflictingWaiters, getLevelMaxLock, getLevelMinLock, getLockLevel, getMaxLevelOwner, getMaxLevelOwner, getMaxLevelOwner, getMaxLevelOwner, getOwner, getResourceId, has, hashCode, isCompatible, registerWaiter, release, setLockLevel, test, toString, tryLock, tryLock, unregisterWaiterpublic static final int NO_LOCK
public static final int READ_LOCK
public static final int UPGRADE_LOCK
public static final int WRITE_LOCK
public ReadWriteUpgradeLock(Object resourceId, LoggerFacade logger)
resourceId - identifier for the resource associated to this locklogger - generic logger used for all kind of debug loggingpublic boolean acquireRead(Object ownerId, long timeoutMSecs) throws InterruptedException
ownerId - a unique id identifying the entity that wants to acquire a
certain lock level on this locktimeoutMSecs - if blocking is enabled by the wait parameter
this specifies the maximum wait time in millisecondstrue if the lock actually was acquiredInterruptedException - when the thread waiting on this method is interruptedpublic boolean acquireUpgrade(Object ownerId, long timeoutMSecs) throws InterruptedException
ownerId - a unique id identifying the entity that wants to acquire a
certain lock level on this locktimeoutMSecs - if blocking is enabled by the wait parameter
this specifies the maximum wait time in millisecondstrue if the lock actually was acquiredInterruptedException - when the thread waiting on this method is interruptedpublic boolean acquireWrite(Object ownerId, long timeoutMSecs) throws InterruptedException
ownerId - a unique id identifying the entity that wants to acquire a
certain lock level on this locktimeoutMSecs - if blocking is enabled by the wait parameter
this specifies the maximum wait time in millisecondstrue if the lock actually was acquiredInterruptedException - when the thread waiting on this method is interruptedpublic boolean acquire(Object ownerId, int targetLockLevel, boolean wait, int compatibility, boolean preferred, long timeoutMSecs) throws InterruptedException
MultiLevelLock2MultiLevelLock.acquire(java.lang.Object, int, boolean, boolean, long)
except that it allows for different compatibility settings. There is an
additional compatibility mode MultiLevelLock2.COMPATIBILITY_SUPPORTthat allows
equal lock levels not to interfere with each other. This is like an
additional shared compatibility and useful when you only want to make
sure not to interfer with lowe levels, but are fine with the same.acquire in interface MultiLevelLock2acquire in class GenericLockownerId - a unique id identifying the entity that wants to acquire a certain lock level on this locktargetLockLevel - the lock level to acquirewait - true if this method shall block when the desired lock level can not be acquiredcompatibility - MultiLevelLock2.COMPATIBILITY_NONEif no additional compatibility is
desired (same as reentrant set to false) ,
MultiLevelLock2.COMPATIBILITY_REENTRANTif lock level by the same
owner shall not affect compatibility (same as reentrant set to
true), or MultiLevelLock2.COMPATIBILITY_SUPPORTif lock levels that
are the same as the desired shall not affect compatibility, or
finally MultiLevelLock2.COMPATIBILITY_REENTRANT_AND_SUPPORTwhich is
a combination of reentrant and supportpreferred - in case this lock request is incompatible with existing ones
and we wait, it shall be granted before other waiting requests
that are not preferredtimeoutMSecs - if blocking is enabled by the wait parameter this specifies the maximum wait time in millisecondstrue if the lock actually was acquiredInterruptedException - when the thread waiting on this method is interruptedGenericLock.acquire(Object, int, boolean, int, boolean, long)Copyright © 2004-2013 The Apache Software Foundation. All Rights Reserved.