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ForwardingLoadingCache (Guava: Google Core Libraries for Java 11.0.1 API)













    






    

    



    
  
    
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com.google.common.cache

    
Class ForwardingLoadingCache<K,V>
    

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

    

    

    All Implemented Interfaces: 
    Function<K,V>, Cache<K,V>, LoadingCache<K,V>
    

    

    

    Direct Known Subclasses: 
    ForwardingLoadingCache.SimpleForwardingLoadingCache
    

    

    

    

    @Beta
public abstract class ForwardingLoadingCache<K,V>
    extends ForwardingCache<K,V>
    implements LoadingCache<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.

    Note that get(K), getUnchecked(K), and apply(K) all expose the same underlying functionality, so should probably be overridden as a group.

    Since:
    11.0
    Author:
    Charles Fry

    Nested Class Summary
    static class ForwardingLoadingCache.SimpleForwardingLoadingCache<K,V>
              A simplified version of ForwardingLoadingCache where subclasses can pass in an already constructed LoadingCache as the delegete.
     
    Nested classes/interfaces inherited from class com.google.common.cache.ForwardingCache
    ForwardingCache.SimpleForwardingCache<K,V>
     
    Constructor Summary
    protected ForwardingLoadingCache()
              Constructor for use by subclasses.
     
    Method Summary
     V apply(K key)
              Discouraged.
    protected abstract  LoadingCache<K,V> delegate()
              Returns the backing delegate instance that methods are forwarded to.
     V get(K key)
              Returns the value associated with key in this cache, first loading that value if necessary.
     ImmutableMap<K,V> getAll(Iterable<? extends K> keys)
              Returns a map of the values associated with keys, creating or retrieving those values if necessary.
     V getUnchecked(K key)
              Returns the value associated with key in this cache, first loading that value if necessary.
     void refresh(K key)
              Loads a new value for key key, possibly asynchronously.
     
    Methods inherited from class com.google.common.cache.ForwardingCache
    asMap, cleanUp, get, getAllPresent, getIfPresent, invalidate, invalidateAll, invalidateAll, put, size, stats
     
    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
     
    Methods inherited from interface com.google.common.cache.LoadingCache
    asMap
     
    Methods inherited from interface com.google.common.cache.Cache
    cleanUp, get, getAllPresent, getIfPresent, invalidate, invalidateAll, invalidateAll, put, size, stats
     
    Methods inherited from interface com.google.common.base.Function
    equals
     

    Constructor Detail

    ForwardingLoadingCache

    protected ForwardingLoadingCache()
    Constructor for use by subclasses.

    Method Detail

    delegate

    protected abstract LoadingCache<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 ForwardingCache<K,V>

    get

    public V get(K key)
      throws ExecutionException
    Description copied from interface: Cache
    Returns the value associated with key in this cache, first loading that value if necessary. No observable state associated with this cache is modified until loading completes.

    Specified by:
    get in interface Cache<K,V>
    Specified by:
    get in interface LoadingCache<K,V>
    Overrides:
    get in class ForwardingCache<K,V>
    Throws:
    ExecutionException - if a checked exception was thrown while loading the value

    getUnchecked

    public V getUnchecked(K key)
    Description copied from interface: Cache
    Returns the value associated with key in this cache, first loading that value if necessary. No observable state associated with this cache is modified until computation completes. Unlike Cache.get(K, java.util.concurrent.Callable), this method does not throw a checked exception, and thus should only be used in situations where checked exceptions are not thrown by the cache loader.

    Warning: this method silently converts checked exceptions to unchecked exceptions, and should not be used with cache loaders which throw checked exceptions.

    Specified by:
    getUnchecked in interface Cache<K,V>
    Specified by:
    getUnchecked in interface LoadingCache<K,V>
    Overrides:
    getUnchecked in class ForwardingCache<K,V>

    getAll

    public ImmutableMap<K,V> getAll(Iterable<? extends K> keys)
                         throws ExecutionException
    Description copied from interface: LoadingCache
    Returns a map of the values associated with keys, creating or retrieving those values if necessary. The returned map contains entries that were already cached, combined with newly loaded entries; it will never contain null keys or values.

    Caches loaded by a CacheLoader will issue a single request to CacheLoader.loadAll(java.lang.Iterable) for all keys which are not already present in the cache. All entries returned by CacheLoader.loadAll(java.lang.Iterable) will be stored in the cache, over-writing any previously cached values. This method will throw an exception if CacheLoader.loadAll(java.lang.Iterable) returns null, returns a map containing null keys or values, or fails to return an entry for each requested key.

    Note that duplicate elements in keys, as determined by Object.equals(java.lang.Object), will be ignored.

    Specified by:
    getAll in interface LoadingCache<K,V>
    Throws:
    ExecutionException - if a checked exception was thrown while loading the values

    apply

    public V apply(K key)
    Description copied from interface: Cache
    Discouraged. Provided to satisfy the Function interface; use Cache.get(K, java.util.concurrent.Callable) or Cache.getUnchecked(K) instead.

    Specified by:
    apply in interface Function<K,V>
    Specified by:
    apply in interface Cache<K,V>
    Specified by:
    apply in interface LoadingCache<K,V>
    Overrides:
    apply in class ForwardingCache<K,V>

    refresh

    public void refresh(K key)
    Description copied from interface: LoadingCache
    Loads a new value for key key, possibly asynchronously. While the new value is loading the previous value (if any) will continue to be returned by get(key) unless it is evicted. If the new value is loaded successfully it will replace the previous value in the cache; if an exception is thrown while refreshing the previous value will remain, and the exception will be logged (using Logger) and swallowed.

    Caches loaded by a CacheLoader will call CacheLoader.reload(K, V) if the cache currently contains a value for key, and CacheLoader.load(K) otherwise.

    Returns without doing anything if another thread is currently loading the value for key. If the cache loader associated with this cache performs refresh asynchronously then this method may return before refresh completes.

    Specified by:
    refresh in interface LoadingCache<K,V>
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