org.apache.jackrabbit.core.cache

Class ConcurrentCache<K,V>

java.lang.Object

org.apache.jackrabbit.core.cache.AbstractCache

org.apache.jackrabbit.core.cache.ConcurrentCache<K,V>

All Implemented Interfaces:

Cache

public class ConcurrentCache<K,V>
extends AbstractCache

Concurrent cache implementation that uses cache segments to minimize the chance of lock contention. The LRU algorithm is used to evict excess entries from each cache segment separately, which makes the combined eviction algorithm similar but not exactly the same as LRU. None of the methods of this class are synchronized, but they are all thread-safe.

Constructor Summary

Constructors

Constructor and Description
ConcurrentCache(String name)
ConcurrentCache(String name, int numberOfSegments)

Method Summary

Modifier and Type	Method and Description
void	clear() Clears all segments of the cache.
boolean	containsKey(K key) Checks if the identified entry is cached.
V	get(K key) Returns the identified cache entry.
long	getElementCount() Get the number of elements/objects in the cache.
boolean	isEmpty() Checks if the cache size is zero.
V	put(K key, V value, long size) Adds the given entry to the cache.
V	remove(K key) Removes the identified entry from the cache.
void	setMaxMemorySize(long size) Sets the maximum size of the cache and evicts any excess items until the current size falls within the given limit.
String	toString()
List<V>	values() Returns all values in the cache.

Methods inherited from class org.apache.jackrabbit.core.cache.AbstractCache

dispose, getAccessCount, getCacheInfoAsString, getMaxMemorySize, getMemoryUsed, getMissCount, getTotalAccessCount, isTooBig, recordCacheAccess, recordCacheMiss, recordSizeChange, resetAccessCount, resetMissCount, setAccessListener

Methods inherited from class java.lang.Object

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

Constructor Detail

ConcurrentCache

public ConcurrentCache(String name,
                       int numberOfSegments)

ConcurrentCache

public ConcurrentCache(String name)

Method Detail

containsKey

public boolean containsKey(K key)

Checks if the identified entry is cached.

Parameters:

key - entry key

Returns:

true if the entry is cached, false otherwise

get

public V get(K key)

Returns the identified cache entry.

Parameters:

key - entry key

Returns:

entry value, or null if not found

values

public List<V> values()

Returns all values in the cache. Note that this method is not synchronized over the entire cache, so it is only guaranteed to return accurate results when there are no concurrent threads modifying the cache.

Returns:

cached values

put

public V put(K key,
             V value,
             long size)

Adds the given entry to the cache.

Parameters:

key - entry key

value - entry value

size - entry size

Returns:

the previous value, or null

remove

public V remove(K key)

Removes the identified entry from the cache.

Parameters:

key - entry key

Returns:

removed entry, or null if not found

clear

public void clear()

Clears all segments of the cache. Note that even this method is not synchronized over the entire cache, so it needs to explicitly count the cache size changes and may return with a non-empty cache if other threads have concurrently been adding new entries.

isEmpty

public boolean isEmpty()

Checks if the cache size is zero.

setMaxMemorySize

public void setMaxMemorySize(long size)

Sets the maximum size of the cache and evicts any excess items until the current size falls within the given limit.

Specified by:

setMaxMemorySize in interface Cache

Overrides:

setMaxMemorySize in class AbstractCache

Parameters:

size - the size in bytes

getElementCount

public long getElementCount()

Description copied from interface: Cache

Get the number of elements/objects in the cache.

Returns:

the number of elements

toString

public String toString()

Overrides:

toString in class Object