oracle.toplink.essentials.internal.identitymaps

Class CacheIdentityMap

java.lang.Object

oracle.toplink.essentials.internal.identitymaps.IdentityMap

oracle.toplink.essentials.internal.identitymaps.FullIdentityMap

oracle.toplink.essentials.internal.identitymaps.CacheIdentityMap

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable

public class CacheIdentityMap
extends FullIdentityMap

Purpose: A fixed size LRU cache

Using a linked list as well as the hashtable from the superclass a LRU cache is maintained. When a get is executed the LRU list is updated and when a new object is inserted the object at the start of the list is deleted (provided the maxSize has been reached).

Responsibilities:

• Guarantees identity through primary key values
• Keeps the LRU linked list updated.

Since:

TOPLink/Java 1.0

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected LinkedCacheKey	first Provide handles on the linked list
protected LinkedCacheKey	last Provide handles on the linked list

Fields inherited from class oracle.toplink.essentials.internal.identitymaps.FullIdentityMap

cacheKeys

Fields inherited from class oracle.toplink.essentials.internal.identitymaps.IdentityMap

maxSize, searchKey

Constructor Summary

Constructors

Constructor and Description
CacheIdentityMap(int size) Initialize newly instantiated CacheIdentityMap.

Method Summary

Modifier and Type	Method and Description
CacheKey	createCacheKey(java.util.Vector primaryKey, java.lang.Object object, java.lang.Object writeLockValue, long readTime)
protected void	ensureFixedSize() Reduces the size of the receiver down to the maxSize removing objects from the start of the linked list.
protected CacheKey	getCacheKey(java.util.Vector primaryKeys) Access the object within the table for the given primaryKey.
protected LinkedCacheKey	insertLink(LinkedCacheKey key) Insert a new element into the linked list of LinkedCacheKeys.
protected void	put(CacheKey cacheKey) Store the object in the identity map with the linked cache key
java.lang.Object	remove(CacheKey key) Remove the LinkedCacheKey from the cache as well as from the linked list.
protected LinkedCacheKey	removeLink(LinkedCacheKey key) Remove the LinkedCacheKey from the linked list.
void	updateMaxSize(int maxSize) INTERNAL: This method will be used to update the max cache size, any objects exceeding the max cache size will be remove from the cache.

Methods inherited from class oracle.toplink.essentials.internal.identitymaps.FullIdentityMap

clone, collectLocks, elements, getCacheKey, getCacheKeys, getSize, getSize, keys, put, resetCacheKey, resetCacheKey, setCacheKeys

Methods inherited from class oracle.toplink.essentials.internal.identitymaps.IdentityMap

acquireDeferredLock, acquireLock, acquireLockNoWait, acquireReadLockOnCacheKey, acquireReadLockOnCacheKeyNoWait, containsKey, createCacheKey, get, getCacheKeyWithReadLock, getDefaultIdentityMapClass, getMaxSize, getSearchKey, getWrapper, getWriteLockValue, initialize, remove, setMaxSize, setSearchKey, setWrapper, setWriteLockValue, toString, updateCacheKey

Methods inherited from class java.lang.Object

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

Field Detail

first

protected LinkedCacheKey first

Provide handles on the linked list

last

protected LinkedCacheKey last

Provide handles on the linked list

Constructor Detail

CacheIdentityMap

public CacheIdentityMap(int size)

Initialize newly instantiated CacheIdentityMap.

Parameters:

size - int The size of the Cache

Method Detail

createCacheKey

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

Overrides:

createCacheKey in class IdentityMap

ensureFixedSize

protected void ensureFixedSize()

Reduces the size of the receiver down to the maxSize removing objects from the start of the linked list.

getCacheKey

protected CacheKey getCacheKey(java.util.Vector primaryKeys)

Access the object within the table for the given primaryKey. Move the accessed key to the top of the order keys linked list to maintain LRU.

Overrides:

getCacheKey in class IdentityMap

Parameters:

aVector - is the primary key for the object to search for.

Returns:

The LinkedCacheKey or null if none found for primaryKey

insertLink

protected LinkedCacheKey insertLink(LinkedCacheKey key)

Insert a new element into the linked list of LinkedCacheKeys. New elements (Recently Used) are added at the end (last).

Returns:

The added LinkedCacheKey

put

protected void put(CacheKey cacheKey)

Store the object in the identity map with the linked cache key

Overrides:

put in class FullIdentityMap

remove

public java.lang.Object remove(CacheKey key)

Remove the LinkedCacheKey from the cache as well as from the linked list.

Overrides:

remove in class FullIdentityMap

Returns:

The LinkedCacheKey to be removed

removeLink

protected LinkedCacheKey removeLink(LinkedCacheKey key)

Remove the LinkedCacheKey from the linked list.

Returns:

The removed LinkedCacheKey

updateMaxSize

public void updateMaxSize(int maxSize)

INTERNAL: This method will be used to update the max cache size, any objects exceeding the max cache size will be remove from the cache. Please note that this does not remove the object from the identityMap, except in the case of the CacheIdentityMap.

Overrides:

updateMaxSize in class IdentityMap