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
@GwtIncompatible 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

    Nested Classes
    Modifier and Type
    Class
    Description
    static class 
    ForwardingCache.SimpleForwardingCache<K,V>
    A simplified version of ForwardingCache where subclasses can pass in an already constructed Cache as the delegate.

  • Constructor Summary

    Constructors
    Modifier
    Constructor
    Description
    protected
    ForwardingCache()
    Constructor for use by subclasses.

  • Method Summary

    Modifier and Type
    Method
    Description
    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 loader if necessary.
    ImmutableMap<K,V>
    getAllPresent(Iterable<? extends Object> keys)
    Returns a map of the values associated with keys in this cache.
    @Nullable 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<? extends Object> 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, or a set of default values if the cache is not recording 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 Details

    • ForwardingCache

      protected ForwardingCache()
      Constructor for use by subclasses.

  • Method Details

    • 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

      public @Nullable 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 loader if necessary. The method improves upon the conventional "if cached, return; otherwise create, cache and return" pattern. For further improvements, use LoadingCache and its get(K) method instead of this one.

      Among the improvements that this method and LoadingCache.get(K) both provide are:

      Among the further improvements that LoadingCache can provide but this method cannot:

      Warning: For any given key, every loader used with it should compute the same value. Otherwise, a call that passes one loader may return the result of another call with a differently behaving loader. For example, a call that requests a short timeout for an RPC may wait for a similar call that requests a long timeout, or a call by an unprivileged user may return a resource accessible only to a privileged user making a similar call. To prevent this problem, create a key object that includes all values that affect the result of the query. Or use LoadingCache.get(K), which lacks the ability to refer to state other than that in the key.

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

      No observable state associated with this cache is modified until loading completes.

      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<? extends Object> 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<? extends Object> 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, or a set of default values if the cache is not recording statistics. All statistics begin at zero and never decrease over the lifetime of the cache.

      Warning: this cache may not be recording statistical data. For example, a cache created using CacheBuilder only does so if the CacheBuilder.recordStats() method was called. If statistics are not being recorded, a CacheStats instance with zero for all values is returned.

      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.

      Iterators from the returned map are at least weakly consistent: they are safe for concurrent use, but if the cache is modified (including by eviction) after the iterator is created, it is undefined which of the changes (if any) will be reflected in that iterator.

      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>