com.sun.appserv.util.cache

Class LruCache

java.lang.Object

com.sun.appserv.util.cache.BaseCache

com.sun.appserv.util.cache.LruCache

All Implemented Interfaces:

Cache

public class LruCache
extends BaseCache

LRUCache in-memory bounded cache with an LRU list

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected static class	LruCache.LruCacheItem default CacheItem class implementation

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

BaseCache.CacheItem

Field Summary

Fields

Modifier and Type	Field and Description
protected int	defaultMaxEntries
protected LruCache.LruCacheItem	head
protected boolean	isUnbounded
protected int	listSize
static long	NO_TIMEOUT
protected LruCache.LruCacheItem	tail
protected long	timeout
protected int	trimCount

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 and Description
LruCache() default constructor
LruCache(int defaultMaxEntries) constructor with specified max entries.

Method Summary

Modifier and Type	Method and 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
void	init(int maxEntries, long timeout, float loadFactor, Properties props) initialize the 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
void	setTimeout(long timeout) sets the timeout value
void	trimExpiredEntries(int maxCount) trim the expired entries from the cache.
protected BaseCache.CacheItem	trimLru(long currentTime) trim one item from the LRU list

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, handleOverflow, hash, incrementAddCount, incrementEntryCount, incrementHitCount, incrementMissCount, incrementOverflowCount, incrementRefreshCount, incrementRemovalCount, init, init, isEmpty, isThresholdReached, keys, loadValue, notifyRefresh, put, put, remove, remove, remove, removeAll, trimItem, values, waitRefresh

Methods inherited from class java.lang.Object

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

Field Detail

NO_TIMEOUT

public static final long NO_TIMEOUT

See Also:

Constant Field Values

head

protected LruCache.LruCacheItem head

tail

protected LruCache.LruCacheItem tail

trimCount

protected int trimCount

listSize

protected int listSize

timeout

protected long timeout

defaultMaxEntries

protected int defaultMaxEntries

isUnbounded

protected boolean isUnbounded

Constructor Detail

LruCache

public LruCache()

default constructor

LruCache

public LruCache(int defaultMaxEntries)

constructor with specified max entries.

Parameters:

defaultMaxEntries - specifies the default max entries to use when the maxEntries is <= 0.

Method Detail

init

public void init(int maxEntries,
                 long timeout,
                 float loadFactor,
                 Properties props)

initialize the cache

Parameters:

maxEntries - maximum number of entries expected in the cache

loadFactor - the load factor

timeout - to be used to trim the expired entries

props - opaque list of properties for a given cache implementation

Throws:

a - generic Exception if the initialization failed

setTimeout

public void setTimeout(long timeout)

sets the timeout value

Parameters:

timeout - to be used to trim the expired entries

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(long currentTime)

trim one item from the LRU list

Parameters:

currentTime - of this operation

Returns:

the item trimmed from cache list synchronization is handled by the caller

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 this function checks if adding the new item results in a overflow; if so, it returns the item to be removed. 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

trimExpiredEntries

public void trimExpiredEntries(int maxCount)

trim the expired entries from the cache.

Specified by:

trimExpiredEntries in interface Cache

Overrides:

trimExpiredEntries in class BaseCache

Parameters:

maxCount - maximum number of invalid entries to trim specify Integer.MAX_VALUE to trim all invalid entries This call is to be scheduled by a thread managed by the container. NOTE: this algorithm assumes that all the entries in the cache have identical timeout (otherwise traversing from tail won't be right).

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()

Description copied from class: BaseCache

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