Package org.eclipse.persistence.internal.identitymaps

Class WeakIdentityMap

java.lang.Object

org.eclipse.persistence.internal.identitymaps.AbstractIdentityMap

org.eclipse.persistence.internal.identitymaps.FullIdentityMap

org.eclipse.persistence.internal.identitymaps.WeakIdentityMap

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable, IdentityMap

Direct Known Subclasses:

HardCacheWeakIdentityMap, SoftIdentityMap

public class WeakIdentityMap
extends FullIdentityMap

Purpose: A WeakIdentityMap holds all objects referenced by the application only. The weak identity map is similar to the full identity map except for the fact that it allows full garbage collection.

Responsibilities:

• Guarantees identity.
• Allows garbage collection.

Since:

TOPLink/Java 1.0

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field	Description
protected int	cleanupCount	Keep track of a counter to amortize cleanup of dead cache keys
protected int	cleanupSize	PERF: Keep track of a cleanup size to avoid cleanup bottleneck for large caches.

Fields inherited from class org.eclipse.persistence.internal.identitymaps.FullIdentityMap

cacheKeys

Fields inherited from class org.eclipse.persistence.internal.identitymaps.AbstractIdentityMap

descriptor, isIsolated, maxSize, session

Constructor Summary

Constructors

Constructor	Description
WeakIdentityMap(int size, ClassDescriptor descriptor, AbstractSession session, boolean isolated)

Method Summary

Modifier and Type	Method	Description
protected void	checkCleanup()	Check if garbage collected cache keys need to be cleaned up.
protected void	cleanupDeadCacheKeys()	Search for any cache keys that have been garbage collected and remove them.
CacheKey	createCacheKey(java.lang.Object primaryKey, java.lang.Object object, java.lang.Object writeLockValue, long readTime)	Create the correct type of CacheKey for this map.
protected CacheKey	putCacheKeyIfAbsent(CacheKey searchKey)	Need to check for cleanup on put.

Methods inherited from class org.eclipse.persistence.internal.identitymaps.FullIdentityMap

clone, cloneKeys, collectLocks, elements, getCacheKey, getCacheKeys, getSize, getSize, keys, keys, lazyRelationshipLoaded, put, remove, resetCacheKey, setCacheKeys

Methods inherited from class org.eclipse.persistence.internal.identitymaps.AbstractIdentityMap

acquireDeferredLock, acquireLock, acquireLockNoWait, acquireLockWithWait, acquireReadLockOnCacheKey, acquireReadLockOnCacheKeyNoWait, containsKey, get, getAllCacheKeysFromIdentityMapWithEntityPK, getAllFromIdentityMapWithEntityPK, getCacheKeyForLock, getCacheKeyWithReadLock, getDefaultIdentityMapClass, getDescriptor, getDescriptorClass, getMaxSize, getWrapper, getWriteLockValue, release, remove, setDescriptor, setMaxSize, setWrapper, setWriteLockValue, toString, updateMaxSize

Methods inherited from class java.lang.Object

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

Field Detail

cleanupCount

protected volatile int cleanupCount

Keep track of a counter to amortize cleanup of dead cache keys

cleanupSize

protected volatile int cleanupSize

PERF: Keep track of a cleanup size to avoid cleanup bottleneck for large caches.

Constructor Detail

WeakIdentityMap

public WeakIdentityMap(int size,
                       ClassDescriptor descriptor,
                       AbstractSession session,
                       boolean isolated)

Method Detail

cleanupDeadCacheKeys

protected void cleanupDeadCacheKeys()

Search for any cache keys that have been garbage collected and remove them. This must be done because although the objects held by the cache keys will garbage collect, the keys themselves will not and must be cleaned up. This is a linear operation so is amortized through the cleanupCount to occur only once per cycle averaging to make the total time still constant.

createCacheKey

public CacheKey createCacheKey(java.lang.Object primaryKey,
                               java.lang.Object object,
                               java.lang.Object writeLockValue,
                               long readTime)

Description copied from class: AbstractIdentityMap

Create the correct type of CacheKey for this map.

Overrides:

createCacheKey in class AbstractIdentityMap

putCacheKeyIfAbsent

protected CacheKey putCacheKeyIfAbsent(CacheKey searchKey)

Need to check for cleanup on put.

Overrides:

putCacheKeyIfAbsent in class FullIdentityMap

checkCleanup

protected void checkCleanup()

Check if garbage collected cache keys need to be cleaned up.