Package org.exoplatform.commons.notification.impl.service.storage.cache

Class FutureCache<K,V,C>

java.lang.Object

org.exoplatform.commons.notification.impl.service.storage.cache.FutureCache<K,V,C>

Type Parameters:

K - the key type parameter

V - the value type parameter

C - the context type parameter

Direct Known Subclasses:

FutureExoCache

public abstract class FutureCache<K,V,C>
extends Object

A future cache that prevents the loading of the same resource twice. This should be used when the resource to load is very expensive or cannot be concurrently retrieved (like a classloading).

The future cache should be used with the get(Object, Object) method, that retrieves an object from the cache. When the object is not found, then the Loader.retrieve(Object, Object) method is used to retrieve the data and then this data is inserted in the cache.

The class is abstract and does not implement a cache technology by itself, the cache implementation is delegated to the contractual methods get(Object) and put(Object, Object). Those methods are intended to be used by the future cache only.

The Loader interface provides a source to retrieve objects to put in the cache. The goal to maintain this interface is to decouple the cache from the object source.

Version:

$Revision$

Author:

Julien Viet

Constructor Summary

Constructors

Constructor	Description
FutureCache(org.exoplatform.commons.cache.future.Loader<K,V,C> loader)

Method Summary

Modifier and Type	Method	Description
V	get(C context, K key)	Perform a cache lookup for the specified key within the specified context.
protected abstract V	get(K key)	Retrieves the cached value corresponding to the specified key from the cache, it must returns null when the key does not exist.
protected abstract void	put(K key, V value)	Updates the cache with a new key/value pair.
protected abstract void	putOnly(K key, V value)	Updates the cache only local mode with a new key/value pair.

Methods inherited from class java.lang.Object

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

Constructor Detail

FutureCache

public FutureCache(org.exoplatform.commons.cache.future.Loader<K,V,C> loader)

Method Detail

get

protected abstract V get(K key)

Retrieves the cached value corresponding to the specified key from the cache, it must returns null when the key does not exist. This method is intended for internal use by the future cache only.

Parameters:

key - the key

Returns:

the cache value

put

protected abstract void put(K key,
                            V value)

Updates the cache with a new key/value pair. This method is intended for internal use by the future cache only.

Parameters:

key - the key

value - the cache value

putOnly

protected abstract void putOnly(K key,
                                V value)

Updates the cache only local mode with a new key/value pair. This method is intended for internal use by the future cache only.

Parameters:

key - the key

value - the cache value

get

public final V get(C context,
                   K key)

Perform a cache lookup for the specified key within the specified context. When the value cannot be loaded (because it does not exist or it failed or anything else that does not come to my mind), the value null is returned.

Parameters:

context - the context in which the resource is accessed

key - the key identifying the resource

Returns:

the value