Interface AsyncLoadingCache<K,V>

Type Parameters:
K - the type of keys maintained by this cache
V - the type of mapped values
All Known Implementing Classes:
BoundedLocalCache.BoundedLocalAsyncLoadingCache, LocalAsyncLoadingCache, UnboundedLocalCache.UnboundedLocalAsyncLoadingCache

@ThreadSafe public interface AsyncLoadingCache<K,V>
A semi-persistent mapping from keys to values. Values are automatically loaded by the cache asynchronously, and are stored in the cache until either evicted or manually invalidated.

Implementations of this interface are expected to be thread-safe, and can be safely accessed by multiple concurrent threads.

  • Method Details

    • getIfPresent

      @CheckForNull CompletableFuture<V> getIfPresent(@Nonnull Object key)
      Returns the future associated with key in this cache, or null if there is no cached future for key.
      Parameters:
      key - key whose associated value is to be returned
      Returns:
      the current (existing or computed) future value to which the specified key is mapped, or null if this map contains no mapping for the key
      Throws:
      NullPointerException - if the specified key is null
    • get

      @Nonnull CompletableFuture<V> get(@Nonnull K key, @Nonnull Function<? super K,? extends V> mappingFunction)
      Returns the future associated with key in this cache, obtaining that value from mappingFunction if necessary. This method provides a simple substitute for the conventional "if cached, return; otherwise create, cache and return" pattern.

      If the specified key is not already associated with a value, attempts to compute its value asynchronously and enters it into this cache unless null. The entire method invocation is performed atomically, so the function is applied at most once per key. If the asynchronous computation fails, the entry will be automatically removed.

      Warning: as with CacheLoader.load(K), mappingFunction must not attempt to update any other mappings of this cache.

      Parameters:
      key - key with which the specified value is to be associated
      mappingFunction - the function to asynchronously compute a value
      Returns:
      the current (existing or computed) future value associated with the specified key
      Throws:
      NullPointerException - if the specified key or mappingFunction is null
    • get

      @Nonnull CompletableFuture<V> get(@Nonnull K key, @Nonnull BiFunction<? super K,Executor,CompletableFuture<V>> mappingFunction)
      Returns the future associated with key in this cache, obtaining that value from mappingFunction if necessary. This method provides a simple substitute for the conventional "if cached, return; otherwise create, cache and return" pattern.

      If the specified key is not already associated with a value, attempts to compute its value asynchronously and enters it into this cache unless null. The entire method invocation is performed atomically, so the function is applied at most once per key. If the asynchronous computation fails, the entry will be automatically removed.

      Warning: as with CacheLoader.load(K), mappingFunction must not attempt to update any other mappings of this cache.

      Parameters:
      key - key with which the specified value is to be associated
      mappingFunction - the function to asynchronously compute a value
      Returns:
      the current (existing or computed) future value associated with the specified key
      Throws:
      NullPointerException - if the specified key or mappingFunction is null
      RuntimeException - or Error if the mappingFunction does when constructing the future, in which case the mapping is left unestablished
    • get

      @Nonnull CompletableFuture<V> get(@Nonnull K key)
      Returns the future associated with key in this cache, obtaining that value from CacheLoader.asyncLoad(K, java.util.concurrent.Executor) if necessary. If the asynchronous computation fails, the entry will be automatically removed.

      If the specified key is not already associated with a value, attempts to compute its value asynchronously and enters it into this cache unless null. The entire method invocation is performed atomically, so the function is applied at most once per key.

      Parameters:
      key - key with which the specified value is to be associated
      Returns:
      the current (existing or computed) future value associated with the specified key
      Throws:
      NullPointerException - if the specified key is null
      RuntimeException - or Error if the CacheLoader does when constructing the future, in which case the mapping is left unestablished
    • getAll

      @Nonnull CompletableFuture<Map<K,V>> getAll(@Nonnull Iterable<? extends K> keys)
      Returns the future of 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. If the any of the asynchronous computations fail, those entries will be automatically removed.

      Caches loaded by a CacheLoader supporting bulk loading will issue a single request to CacheLoader.asyncLoadAll(java.lang.Iterable<? extends K>, java.util.concurrent.Executor) for all keys which are not already present in the cache. If another call to get(K, java.util.function.Function<? super K, ? extends V>) tries to load the value for a key in keys, that thread simply waits for this computation to finish and returns the loaded value. Caches that do not use a CacheLoader with an optimized bulk load implementation will sequentially load each key by making individual CacheLoader.asyncLoad(K, java.util.concurrent.Executor) calls. Note that multiple threads can concurrently load values for distinct keys.

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

      Parameters:
      keys - the keys whose associated values are to be returned
      Returns:
      the future containing an unmodifiable mapping of keys to values for the specified keys in this cache
      Throws:
      NullPointerException - if the specified collection is null or contains a null element
      RuntimeException - or Error if the CacheLoader does so, if CacheLoader.asyncLoadAll(java.lang.Iterable<? extends K>, java.util.concurrent.Executor) returns null, or fails when constructing the future, in which case the mapping is left unestablished
    • put

      void put(@Nonnull K key, @Nonnull CompletableFuture<V> valueFuture)
      Associates value with key in this cache. If the cache previously contained a value associated with key, the old value is replaced by value. If the asynchronous computation fails, the entry will be automatically removed.

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

      Parameters:
      key - key with which the specified value is to be associated
      valueFuture - value to be associated with the specified key
      Throws:
      NullPointerException - if the specified key or value is null
    • synchronous

      @Nonnull LoadingCache<K,V> synchronous()
      Returns a view of the entries stored in this cache as a synchronous LoadingCache. A mapping is not present if the value is currently being loaded. Modifications made to the synchronous cache directly affect the asynchronous cache. If a modification is made to a mapping that is currently loading, the operation blocks until the computation completes.
      Returns:
      a thread-safe synchronous view of this cache