org.apache.jackrabbit.core.state
Class MLRUItemStateCache

java.lang.Object
  org.apache.jackrabbit.core.state.MLRUItemStateCache

All Implemented Interfaces:

Cache, ItemStateCache

public class MLRUItemStateCache
extends Object
implements ItemStateCache, Cache

An ItemStateCache implementation that internally uses a LinkedMap to maintain a cache of ItemState objects. The cache uses a rough estimate of the memory consumption of the cached item states for calculating the maximum number of entries. The oldest entries are flushed once the cache size has exceeded a certain limit.

TODO rename class to something more appropriate, e.g. FIFOItemSateCache since it doesn't use a LRU eviction policy anymore.

Field Summary

static int

DEFAULT_MAX_MEM default maximum memory to use

Constructor Summary

MLRUItemStateCache()
Constructs a new, empty ItemStateCache with a maximum amount of memory of DEFAULT_MAX_MEM.

Method Summary

void	cache(ItemState state) Stores the specified ItemState object in the map using its ItemId as the key.
void	dispose() Informs the cache that it is no longer in use.
void	evict(ItemId id) Removes the ItemState object with the specified id from this cache if it is present.
void	evictAll() Clears all entries from this cache.
long	getAccessCount() Get the number of accesses (get or set) until resetAccessCount was called.
long	getMaxMemorySize() Get the current limit.
long	getMemoryUsed() Get the amount of used memory.
boolean	isCached(ItemId id) Returns true if this cache contains an ItemState object with the specified id.
boolean	isEmpty() Returns true if this cache contains no entries.
Set	keySet() Returns an unmodifiable set view of the keys (i.e.
void	resetAccessCount() Reset the access counter.
ItemState	retrieve(ItemId id) Returns the ItemState object with the specified id if it is present or null if no entry exists with that id.
void	setAccessListener(CacheAccessListener listener) Set the cache access listener.
void	setMaxMemorySize(long size) Set the new memory limit.
int	size() Returns the number of entries in this cache.
void	update(ItemId id) Informs the cache that the item was modified and the cache might need to recalc the items caching weight.
Collection	values() Returns an unmodifiable collection view of the values (i.e.

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_MAX_MEM

public static final int DEFAULT_MAX_MEM

default maximum memory to use

See Also:

Constant Field Values

Constructor Detail

MLRUItemStateCache

public MLRUItemStateCache()

Constructs a new, empty ItemStateCache with a maximum amount of memory of DEFAULT_MAX_MEM.

Method Detail

isCached

public boolean isCached(ItemId id)

Returns true if this cache contains an ItemState object with the specified id.

Specified by:

isCached in interface ItemStateCache

Parameters:

id - id of ItemState object whose presence should be tested.

Returns:

true if there's a corresponding cache entry, otherwise false.

retrieve

public ItemState retrieve(ItemId id)

Returns the ItemState object with the specified id if it is present or null if no entry exists with that id.

Specified by:

retrieve in interface ItemStateCache

Parameters:

id - the id of the ItemState object to be returned.

Returns:

the ItemState object with the specified id or or null if no entry exists with that id

update

public void update(ItemId id)

Informs the cache that the item was modified and the cache might need to recalc the items caching weight.

Specified by:

update in interface ItemStateCache

Parameters:

id - the id of the item that was modified.

cache

public void cache(ItemState state)

Stores the specified ItemState object in the map using its ItemId as the key.

Specified by:

cache in interface ItemStateCache

Parameters:

state - the ItemState object to cache

evict

public void evict(ItemId id)

Removes the ItemState object with the specified id from this cache if it is present.

Specified by:

evict in interface ItemStateCache

Parameters:

id - the id of the ItemState object which should be removed from this cache.

evictAll

public void evictAll()

Clears all entries from this cache.

Specified by:

evictAll in interface ItemStateCache

isEmpty

public boolean isEmpty()

Returns true if this cache contains no entries.

Specified by:

isEmpty in interface ItemStateCache

Returns:

true if this cache contains no entries.

size

public int size()

Returns the number of entries in this cache.

Specified by:

size in interface ItemStateCache

Returns:

number of entries in this cache.

keySet

public Set keySet()

Returns an unmodifiable set view of the keys (i.e. ItemId objects) of the cached entries.

Specified by:

keySet in interface ItemStateCache

Returns:

a set view of the keys of the cached entries.

values

public Collection values()

Returns an unmodifiable collection view of the values (i.e. ItemState objects) contained in this cache.

Specified by:

values in interface ItemStateCache

Returns:

a collection view of the values contained in this cache.

getAccessCount

public long getAccessCount()

Get the number of accesses (get or set) until resetAccessCount was called.

Specified by:

getAccessCount in interface Cache

Returns:

the count

getMaxMemorySize

public long getMaxMemorySize()

Get the current limit.

Specified by:

getMaxMemorySize in interface Cache

Returns:

the size in bytes

getMemoryUsed

public long getMemoryUsed()

Get the amount of used memory.

Specified by:

getMemoryUsed in interface Cache

Returns:

the size in bytes

resetAccessCount

public void resetAccessCount()

Reset the access counter.

Specified by:

resetAccessCount in interface Cache

setMaxMemorySize

public void setMaxMemorySize(long size)

Set the new memory limit.

Specified by:

setMaxMemorySize in interface Cache

Parameters:

size - the size in bytes

setAccessListener

public void setAccessListener(CacheAccessListener listener)

Set the cache access listener. Only one listener per cache is supported.

Specified by:

setAccessListener in interface Cache

Parameters:

listener - the new listener

dispose

public void dispose()

Informs the cache that it is no longer in use.

Specified by:

dispose in interface ItemStateCache