org.apache.jcs.engine.memory.lru
Class LRUMemoryCache

java.lang.Object
  org.apache.jcs.engine.memory.AbstractMemoryCache
      org.apache.jcs.engine.memory.lru.LRUMemoryCache

All Implemented Interfaces:

MemoryCache, java.io.Serializable

public class LRUMemoryCache

extends AbstractMemoryCache

A fast reference management system. The least recently used items move to the end of the list and get spooled to disk if the cache hub is configured to use a disk cache. Most of the cache bottelnecks are in IO. There are no io bottlenecks here, it's all about processing power. Even though there are only a few adjustments necessary to maintain the double linked list, we might want to find a more efficient memory manager for large cache regions. The LRUMemoryCache is most efficeint when the first element is selected. The smaller the region, the better the chance that this will be the case. < .04 ms per put, p3 866, 1/10 of that per get

Version:

$Id: LRUMemoryCache.java,v 1.21 2003/08/22 11:57:19 mpoeschl Exp $

Author:

Aaron Smuts, James Taylor, John McNally

See Also:

Serialized Form

Nested Class Summary

class	LRUMemoryCache.IteratorWrapper
class	LRUMemoryCache.MapEntryWrapper

Field Summary

private MemoryElementDescriptor	first
private MemoryElementDescriptor	last
private static org.apache.commons.logging.Log	log

Fields inherited from class org.apache.jcs.engine.memory.AbstractMemoryCache

attr, cache, cacheName, cattr, chunkSize, map, status

Constructor Summary

LRUMemoryCache()

Method Summary

private void	addFirst(ICacheElement ce) Adds a new node to the start of the link list.
private void	addLast(CacheElement ce) Adds a new node to the end of the link list.
void	dumpCacheEntries() Dump the cache entries from first to list for debugging.
private int	dumpCacheSize()
void	dumpMap() Dump the cache map for debugging.
ICacheElement	get(java.io.Serializable key) Get an item from the cache
java.util.Iterator	getIterator() Gets the iterator attribute of the LRUMemoryCache object
java.lang.Object[]	getKeyArray() Get an Array of the keys for all elements in the memory cache
ICacheElement	getQuiet(java.io.Serializable key) Get an item from the cache without affecting its last access time or position.
void	initialize(CompositeCache hub) For post reflection creation initialization
void	makeFirst(ICacheElement ce) Moves an existing node to the start of the link list.
void	makeFirst(MemoryElementDescriptor me) Moves an existing node to the start of the link list.
boolean	remove(java.io.Serializable key) Removes an item from the cache.
void	removeAll() Remove all of the elements from both the Map and the linked list implementation.
private void	removeNode(MemoryElementDescriptor me) Removes the specified node from the link list.
void	update(ICacheElement ce) Puts an item to the cache.
private void	verifyCache()
private void	verifyCache(java.io.Serializable key)

Methods inherited from class org.apache.jcs.engine.memory.AbstractMemoryCache

dispose, getCacheAttributes, getCacheName, getCompositeCache, getGroupKeys, getSize, getStats, getStatus, setCacheAttributes, waterfal

Methods inherited from class java.lang.Object

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

Field Detail

log

private static final org.apache.commons.logging.Log log

first

private MemoryElementDescriptor first

last

private MemoryElementDescriptor last

Constructor Detail

LRUMemoryCache

public LRUMemoryCache()

Method Detail

initialize

public void initialize(CompositeCache hub)

For post reflection creation initialization

Specified by:

initialize in interface MemoryCache

Overrides:

initialize in class AbstractMemoryCache

Parameters:

hub -

update

public void update(ICacheElement ce)
            throws java.io.IOException

Puts an item to the cache.

Specified by:

update in interface MemoryCache

Specified by:

update in class AbstractMemoryCache

Parameters:

ce - Description of the Parameter

Throws:

java.io.IOException

removeAll

public void removeAll()
               throws java.io.IOException

Remove all of the elements from both the Map and the linked list implementation. Overrides base class.

Specified by:

removeAll in interface MemoryCache

Overrides:

removeAll in class AbstractMemoryCache

Throws:

java.io.IOException

getQuiet

public ICacheElement getQuiet(java.io.Serializable key)
                       throws java.io.IOException

Get an item from the cache without affecting its last access time or position.

Specified by:

getQuiet in interface MemoryCache

Specified by:

getQuiet in class AbstractMemoryCache

Parameters:

key - Identifies item to find

Returns:

Element mathinh key if found, or null

Throws:

java.io.IOException

get

public ICacheElement get(java.io.Serializable key)
                  throws java.io.IOException

Get an item from the cache

Specified by:

get in interface MemoryCache

Specified by:

get in class AbstractMemoryCache

Parameters:

key - Identifies item to find

Returns:

ICacheElement if found, else null

Throws:

java.io.IOException

remove

public boolean remove(java.io.Serializable key)
               throws java.io.IOException

Removes an item from the cache. This method handles hierarchical removal. If the key is a String and ends with the CacheConstants.NAME_COMPONENT_DELIMITER, then all items with keys starting with the argument String will be removed.

Specified by:

remove in interface MemoryCache

Specified by:

remove in class AbstractMemoryCache

Parameters:

key -

Returns:

Throws:

java.io.IOException

getIterator

public java.util.Iterator getIterator()

Gets the iterator attribute of the LRUMemoryCache object

Specified by:

getIterator in interface MemoryCache

Overrides:

getIterator in class AbstractMemoryCache

Returns:

The iterator value

getKeyArray

public java.lang.Object[] getKeyArray()

Get an Array of the keys for all elements in the memory cache

Specified by:

getKeyArray in interface MemoryCache

Specified by:

getKeyArray in class AbstractMemoryCache

Returns:

An Object[]

removeNode

private void removeNode(MemoryElementDescriptor me)

Removes the specified node from the link list.

Parameters:

me - Description of the Parameter

addLast

private void addLast(CacheElement ce)

Adds a new node to the end of the link list. Currently not used.

Parameters:

ce - The feature to be added to the Last

addFirst

private void addFirst(ICacheElement ce)

Adds a new node to the start of the link list.

Parameters:

ce - The feature to be added to the First

makeFirst

public void makeFirst(ICacheElement ce)

Moves an existing node to the start of the link list.

Parameters:

ce - Description of the Parameter

makeFirst

public void makeFirst(MemoryElementDescriptor me)

Moves an existing node to the start of the link list.

Parameters:

me - Description of the Parameter

dumpMap

public void dumpMap()

Dump the cache map for debugging.

dumpCacheEntries

public void dumpCacheEntries()

Dump the cache entries from first to list for debugging.

dumpCacheSize

private int dumpCacheSize()

verifyCache

private void verifyCache()

verifyCache

private void verifyCache(java.io.Serializable key)