org.eclipse.persistence.internal.identitymaps

Class SoftCacheWeakIdentityMap

java.lang.Object

org.eclipse.persistence.internal.identitymaps.AbstractIdentityMap

org.eclipse.persistence.internal.identitymaps.FullIdentityMap

org.eclipse.persistence.internal.identitymaps.WeakIdentityMap

org.eclipse.persistence.internal.identitymaps.HardCacheWeakIdentityMap

org.eclipse.persistence.internal.identitymaps.SoftCacheWeakIdentityMap

All Implemented Interfaces:

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

public class SoftCacheWeakIdentityMap
extends HardCacheWeakIdentityMap

Purpose: A SoftCacheWeakIdentityMap is identical to the WeakIdentityMap, however the weak reference can be a performance problem for some types of apps because it can cause too much garbage collection of objects read causing them to be re-read and re-built (this defeats the purpose of the cache). The SoftCacheWeakIdentityMap solves this through also holding a fixed number of objects in memory to improve caching.

Responsibilities:

• Guarantees identity
• Allows garbage collection
• Increases performance by maintaining a fixed size cache of MRU objects when memory is available.
• The default size of the reference cache is the max size.

Since:

TOPLink/Java 1.2

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class org.eclipse.persistence.internal.identitymaps.HardCacheWeakIdentityMap

HardCacheWeakIdentityMap.ReferenceCacheKey

Constructor Summary

Constructors

Constructor and Description
SoftCacheWeakIdentityMap(int size, ClassDescriptor descriptor, AbstractSession session, boolean isIsolated)

Method Summary

Modifier and Type	Method and Description
java.lang.Object	buildReference(java.lang.Object object) Creates a Soft reference to the object.
boolean	hasReference(java.lang.Object reference) Checks if the object is null, or reference's object is null.

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

createCacheKey, getReferenceCache, put, remove, updateMaxSize

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

clone, collectLocks, elements, getCacheKey, getCacheKeys, getSize, getSize, keys, keys, lazyRelationshipLoaded, resetCacheKey

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

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

Methods inherited from class java.lang.Object

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

Constructor Detail

SoftCacheWeakIdentityMap

public SoftCacheWeakIdentityMap(int size,
                                ClassDescriptor descriptor,
                                AbstractSession session,
                                boolean isIsolated)

Method Detail

buildReference

public java.lang.Object buildReference(java.lang.Object object)

Creates a Soft reference to the object.

Overrides:

buildReference in class HardCacheWeakIdentityMap

Parameters:

object - is the domain object to cache.

hasReference

public boolean hasReference(java.lang.Object reference)

Checks if the object is null, or reference's object is null.

Overrides:

hasReference in class HardCacheWeakIdentityMap

Parameters:

the - object for hard or the reference for soft.