BiLevelCacheMap

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org.apache.myfaces.util
Class BiLevelCacheMap

java.lang.Object
  org.apache.myfaces.util.BiLevelCacheMap

All Implemented Interfaces:: java.util.Map

public abstract class BiLevelCacheMap
extends java.lang.Object
implements java.util.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.

Version:: $Revision: 169655 $ $Date: 2005-05-11 12:45:06 -0400 (Wed, 11 May 2005) $

Nested Class Summary

Nested classes inherited from class java.util.Map

java.util.Map.Entry

Field Summary

protected java.util.Map _cacheL1
          To preinitialize _cacheL1 with default values use an initialization block

private java.util.Map _cacheL2
          Must be final because it is used for synchronization

private int _mergeThreshold


private int _missCount


private static int INITIAL_SIZE_L1


Constructor Summary

BiLevelCacheMap(int mergeThreshold)


Method Summary

void clear()
          Remove all entries from this Map (optional operation).

boolean containsKey(java.lang.Object key)
          Returns true if this contains a mapping for the given key.

boolean containsValue(java.lang.Object value)
          Returns true if this contains at least one mapping with the given value.

java.util.Set entrySet()
          Returns a set view of the mappings in this Map.

java.lang.Object get(java.lang.Object key)
          Returns the value mapped by the given key.

boolean isEmpty()
          Returns true if the map contains no mappings.

java.util.Set keySet()
          Returns a set view of the keys in this Map.

private void merge(java.util.Map map)


private void mergeIfL2NotEmpty()


private void mergeIfNeeded()


protected abstract java.lang.Object newInstance(java.lang.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.

java.lang.Object put(java.lang.Object key, java.lang.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(java.util.Map map)
          Copies all entries of the given map to this one (optional operation).

java.lang.Object remove(java.lang.Object key)
          This operation is very expensive.

int size()
          Returns the number of key-value mappings in the map.

java.util.Collection values()
          Returns a collection (or bag) view of the values in this Map.

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Map

equals, hashCode

Field Detail

INITIAL_SIZE_L1

private static final int INITIAL_SIZE_L1

See Also:: Constant Field Values

_cacheL1

protected java.util.Map _cacheL1

To preinitialize _cacheL1 with default values use an initialization block

_cacheL2

private final java.util.Map _cacheL2

Must be final because it is used for synchronization

_mergeThreshold

private final int _mergeThreshold

_missCount

private int _missCount

Constructor Detail

BiLevelCacheMap

public BiLevelCacheMap(int mergeThreshold)

Method Detail