Package com.sun.appserv.util.cache

Class MultiLruCache

java.lang.Object

com.sun.appserv.util.cache.BaseCache

com.sun.appserv.util.cache.MultiLruCache

All Implemented Interfaces:

Cache

Direct Known Subclasses:

BoundedMultiLruCache

public class MultiLruCache
extends BaseCache

MultiLruCache -- in-memory bounded LRU cache with multiple LRU lists Underlying Hashtable is made into logical segments, with each segment having its own LRU list.

Nested Class Summary

Nested classes/interfaces inherited from class com.sun.appserv.util.cache.BaseCache

BaseCache.CacheItem

Field Summary

Fields

Modifier and Type	Field	Description
static final int	DEFAULT_HASHTABLE_SEGMENT_SIZE
protected int[]	listsLength
static final int	LRU_HEAD
static final int	LRU_TAIL

Fields inherited from class com.sun.appserv.util.cache.BaseCache

bucketLocks, buckets, entryCount, hitCount, listeners, maxBuckets, maxEntries, missCount, refreshFlags, removalCount, threshold

Constructor Summary

Constructors

Constructor	Description
MultiLruCache()

Method Summary

Modifier and Type	Method	Description
protected BaseCache.CacheItem	createItem(int hashCode, Object key, Object value, int size)	create new item
Object	getStatByName(String key)	get the desired statistic counter
Map	getStats()	get the stats snapshot
protected void	handleOverflow()	cache has reached threshold so trim its size. subclasses are expected to provide a robust cache replacement algorithm.
protected void	incrementTrimIndex()
void	init(int maxCapacity, Properties props)	initialize the LRU cache
protected void	itemAccessed(BaseCache.CacheItem item)	this item is accessed
protected BaseCache.CacheItem	itemAdded(BaseCache.CacheItem item)	this item is just added to the cache
protected void	itemRefreshed(BaseCache.CacheItem item, int oldSize)	item value has been refreshed
protected void	itemRemoved(BaseCache.CacheItem item)	item value has been removed from the cache
protected BaseCache.CacheItem	trimLru(int segment)	remove an lru item from one of the LRU lists

Methods inherited from class com.sun.appserv.util.cache.BaseCache

_put, _remove, _removeItem, add, add, addCacheListener, clear, clearStats, contains, decrementEntryCount, destroy, elements, eq, get, get, getAll, getEntryCount, getIndex, getIndex, hash, incrementAddCount, incrementEntryCount, incrementHitCount, incrementMissCount, incrementOverflowCount, incrementRefreshCount, incrementRemovalCount, init, isEmpty, isThresholdReached, keys, loadValue, notifyRefresh, put, put, remove, remove, remove, removeAll, trimExpiredEntries, trimItem, values, waitRefresh

Methods inherited from class java.lang.Object

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

Field Details

LRU_HEAD

public static final int LRU_HEAD

See Also:

• Constant Field Values

LRU_TAIL

public static final int LRU_TAIL

See Also:

• Constant Field Values

DEFAULT_HASHTABLE_SEGMENT_SIZE

public static final int DEFAULT_HASHTABLE_SEGMENT_SIZE

See Also:

• Constant Field Values

listsLength

protected int[] listsLength

Constructor Details

MultiLruCache

public MultiLruCache()

Method Details

init

public void init(int maxCapacity,
 Properties props)
          throws Exception

initialize the LRU cache

Specified by:

init in interface Cache

Overrides:

init in class BaseCache

Parameters:

maxCapacity - maximum number of entries this cache may hold

props - opaque list of properties for a given cache implementation

Throws:

Exception

createItem

protected BaseCache.CacheItem createItem(int hashCode,
 Object key,
 Object value,
 int size)

create new item

Overrides:

createItem in class BaseCache

Parameters:

hashCode - for the entry

key - Object key

value - Object value

size - size in bytes of the item subclasses may override to provide their own CacheItem extensions e.g. one that permits persistence.

trimLru

protected BaseCache.CacheItem trimLru(int segment)

remove an lru item from one of the LRU lists

Parameters:

the - LRU segment index to trim

Returns:

the item that was successfully trimmed

itemAdded

protected BaseCache.CacheItem itemAdded(BaseCache.CacheItem item)

this item is just added to the cache

Overrides:

itemAdded in class BaseCache

Parameters:

item - CacheItem that was created

Returns:

a overflow item; may be null Cache bucket is already synchronized by the caller

itemAccessed

protected void itemAccessed(BaseCache.CacheItem item)

this item is accessed

Overrides:

itemAccessed in class BaseCache

Parameters:

item - CacheItem accessed Cache bucket is already synchronized by the caller

itemRefreshed

protected void itemRefreshed(BaseCache.CacheItem item,
 int oldSize)

item value has been refreshed

Overrides:

itemRefreshed in class BaseCache

Parameters:

item - CacheItem that was refreshed

oldSize - size of the previous value that was refreshed Cache bucket is already synchronized by the caller

itemRemoved

protected void itemRemoved(BaseCache.CacheItem item)

item value has been removed from the cache

Overrides:

itemRemoved in class BaseCache

Parameters:

item - CacheItem that was just removed Cache bucket is already synchronized by the caller

handleOverflow

protected void handleOverflow()

cache has reached threshold so trim its size. subclasses are expected to provide a robust cache replacement algorithm.

Overrides:

handleOverflow in class BaseCache

incrementTrimIndex

protected void incrementTrimIndex()

getStatByName

public Object getStatByName(String key)

get the desired statistic counter

Specified by:

getStatByName in interface Cache

Overrides:

getStatByName in class BaseCache

Parameters:

key - to corresponding stat

Returns:

an Object corresponding to the stat See also: Constant.java for the key

getStats

public Map getStats()

get the stats snapshot

Specified by:

getStats in interface Cache

Overrides:

getStats in class BaseCache

Returns:

a Map of stats See also: Constant.java for the keys