com.google.common.cache
Class ForwardingCache<K,V>

java.lang.Object
  com.google.common.collect.ForwardingObject
      com.google.common.cache.ForwardingCache<K,V>

All Implemented Interfaces:

Cache<K,V>

Direct Known Subclasses:

ForwardingCache.SimpleForwardingCache, ForwardingLoadingCache

@Beta
public abstract class ForwardingCache<K,V>
extends ForwardingObject
implements Cache<K,V>

A cache which forwards all its method calls to another cache. Subclasses should override one or more methods to modify the behavior of the backing cache as desired per the decorator pattern.

Since:

10.0

Author:

Charles Fry

Nested Class Summary

static class

ForwardingCache.SimpleForwardingCache<K,V> A simplified version of ForwardingCache where subclasses can pass in an already constructed Cache as the delegete.

Constructor Summary

protected

ForwardingCache() Constructor for use by subclasses.

Method Summary

ConcurrentMap<K,V>	asMap() Returns a view of the entries stored in this cache as a thread-safe map.
void	cleanUp() Performs any pending maintenance operations needed by the cache.
protected abstract Cache<K,V>	delegate() Returns the backing delegate instance that methods are forwarded to.
V	get(K key, Callable<? extends V> valueLoader) Returns the value associated with key in this cache, obtaining that value from valueLoader if necessary.
ImmutableMap<K,V>	getAllPresent(Iterable<?> keys) Returns a map of the values associated with keys in this cache.
V	getIfPresent(Object key) Returns the value associated with key in this cache, or null if there is no cached value for key.
void	invalidate(Object key) Discards any cached value for key key.
void	invalidateAll() Discards all entries in the cache.
void	invalidateAll(Iterable<?> keys) Discards any cached values for keys keys.
void	put(K key, V value) Associates value with key in this cache.
void	putAll(Map<? extends K,? extends V> m) Copies all of the mappings from the specified map to the cache.
long	size() Returns the approximate number of entries in this cache.
CacheStats	stats() Returns a current snapshot of this cache's cumulative statistics.

Methods inherited from class com.google.common.collect.ForwardingObject

toString

Methods inherited from class java.lang.Object

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

Constructor Detail

ForwardingCache

protected ForwardingCache()

Constructor for use by subclasses.

Method Detail

delegate

protected abstract Cache<K,V> delegate()

Description copied from class: ForwardingObject

Returns the backing delegate instance that methods are forwarded to. Abstract subclasses generally override this method with an abstract method that has a more specific return type, such as ForwardingSet.delegate(). Concrete subclasses override this method to supply the instance being decorated.

Specified by:

delegate in class ForwardingObject

getIfPresent

@Nullable
public V getIfPresent(Object key)

Description copied from interface: Cache

Returns the value associated with key in this cache, or null if there is no cached value for key.

Specified by:

getIfPresent in interface Cache<K,V>

Since:

11.0

get

public V get(K key,
             Callable<? extends V> valueLoader)
      throws ExecutionException

Description copied from interface: Cache

Returns the value associated with key in this cache, obtaining that value from valueLoader if necessary. No observable state associated with this cache is modified until loading completes. This method provides a simple substitute for the conventional "if cached, return; otherwise create, cache and return" pattern.

Warning: as with CacheLoader.load(K), valueLoader must not return null; it may either return a non-null value or throw an exception.

Specified by:

get in interface Cache<K,V>

Throws:

ExecutionException - if a checked exception was thrown while loading the value

Since:

11.0

getAllPresent

public ImmutableMap<K,V> getAllPresent(Iterable<?> keys)

Description copied from interface: Cache

Returns a map of the values associated with keys in this cache. The returned map will only contain entries which are already present in the cache.

Specified by:

getAllPresent in interface Cache<K,V>

Since:

11.0

put

public void put(K key,
                V value)

Description copied from interface: Cache

Associates value with key in this cache. If the cache previously contained a value associated with key, the old value is replaced by value.

Prefer Cache.get(Object, Callable) when using the conventional "if cached, return; otherwise create, cache and return" pattern.

Specified by:

put in interface Cache<K,V>

Since:

11.0

putAll

public void putAll(Map<? extends K,? extends V> m)

Description copied from interface: Cache

Copies all of the mappings from the specified map to the cache. The effect of this call is equivalent to that of calling put(k, v) on this map once for each mapping from key k to value v in the specified map. The behavior of this operation is undefined if the specified map is modified while the operation is in progress.

Specified by:

putAll in interface Cache<K,V>

Since:

12.0

invalidate

public void invalidate(Object key)

Description copied from interface: Cache

Discards any cached value for key key.

Specified by:

invalidate in interface Cache<K,V>

invalidateAll

public void invalidateAll(Iterable<?> keys)

Description copied from interface: Cache

Discards any cached values for keys keys.

Specified by:

invalidateAll in interface Cache<K,V>

Since:

11.0

invalidateAll

public void invalidateAll()

Description copied from interface: Cache

Discards all entries in the cache.

Specified by:

invalidateAll in interface Cache<K,V>

size

public long size()

Description copied from interface: Cache

Returns the approximate number of entries in this cache.

Specified by:

size in interface Cache<K,V>

stats

public CacheStats stats()

Description copied from interface: Cache

Returns a current snapshot of this cache's cumulative statistics. All stats are initialized to zero, and are monotonically increasing over the lifetime of the cache.

Specified by:

stats in interface Cache<K,V>

asMap

public ConcurrentMap<K,V> asMap()

Description copied from interface: Cache

Returns a view of the entries stored in this cache as a thread-safe map. Modifications made to the map directly affect the cache.

Specified by:

asMap in interface Cache<K,V>

cleanUp

public void cleanUp()

Description copied from interface: Cache

Performs any pending maintenance operations needed by the cache. Exactly which activities are performed -- if any -- is implementation-dependent.

Specified by:

cleanUp in interface Cache<K,V>