org.apache.myfaces.util
Class BiLevelCacheMap
java.lang.Object
org.apache.myfaces.util.BiLevelCacheMap
- Map
public abstract class BiLevelCacheMap
extends java.lang.Object
implements Map
A bi-level cache based on HashMap for caching objects with minimal sychronization
overhead. The limitation is that
remove()
is very expensive.
Access to L1 map is not sychronized, to L2 map is synchronized. New values
are first stored in L2. Once there have been more that a specified mumber of
misses on L1, L1 and L2 maps are merged and the new map assigned to L1
and L2 cleared.
IMPORTANT:entrySet(), keySet(), and values() return unmodifiable snapshot collections.
$Revision: 169655 $ $Date: 2005-05-11 18:45:06 +0200 (Wed, 11 May 2005) $- Anton Koinov (latest modification by $Author: grantsmith $)
protected Map | _cacheL1 - To preinitialize
_cacheL1 with default values use an initialization block
|
void | clear()
|
boolean | containsKey(Object key)
|
boolean | containsValue(Object value)
|
Set | entrySet()
|
Object | get(Object key)
|
boolean | isEmpty()
|
Set | keySet()
|
protected abstract Object | newInstance(Object key) - Subclasses must implement to have automatic creation of new instances
or alternatively can use
put to add new items to the cache.
Implementing this method is prefered to guarantee that there will be only
one instance per key ever created.
|
Object | put(Object key, Object value) - If key is already in cacheL1, the new value will show with a delay,
since merge L2->L1 may not happen immediately.
|
void | putAll(Map map)
|
Object | remove(Object key) - This operation is very expensive.
|
int | size()
|
Collection | values()
|
_cacheL1
protected Map _cacheL1
To preinitialize _cacheL1
with default values use an initialization block
BiLevelCacheMap
public BiLevelCacheMap(int mergeThreshold)
containsKey
public boolean containsKey(Object key)
containsValue
public boolean containsValue(Object value)
entrySet
public Set entrySet()
get
public Object get(Object key)
isEmpty
public boolean isEmpty()
keySet
public Set keySet()
newInstance
protected abstract Object newInstance(Object key)
Subclasses must implement to have automatic creation of new instances
or alternatively can use put
to add new items to the cache.
Implementing this method is prefered to guarantee that there will be only
one instance per key ever created. Calling put() to add items in a multi-
threaded situation will require external synchronization to prevent two
instances for the same key, which defeats the purpose of this cache
(put() is useful when initialization is done during startup and items
are not added during execution or when (temporarily) having possibly two
or more instances of the same key is not of concern).
- new instace for the requested key
put
public Object put(Object key,
Object value)
If key is already in cacheL1, the new value will show with a delay,
since merge L2->L1 may not happen immediately. To force the merge sooner,
call size()
.
putAll
public void putAll(Map map)
remove
public Object remove(Object key)
This operation is very expensive. A full copy of the Map is created
values
public Collection values()