@Beta @GwtCompatible public interface LoadingCache<K,V> extends Cache<K ,V>, Function <K ,V>
Implementations of this interface are expected to be thread-safe, and can be safely accessed by multiple concurrent threads.
When evaluated as a Function, a cache yields the same result as invoking getUnchecked(K).
Note that while this class is still annotated as Beta, the API is frozen from a consumer's standpoint. In other words existing methods are all considered non-Beta and won't be changed without going through an 18 month deprecation cycle; however new methods may be added at any time.
| Modifier and Type | Method and Description |
|---|---|
V |
apply(K key)
Deprecated.
Provided to satisfy the
Function interface; use get(K) or getUnchecked(K) instead.
|
ConcurrentMap |
asMap()
Returns a view of the entries stored in this cache as a thread-safe map.
|
V |
get(K key)
Returns the value associated with
key in this cache, first loading that value if necessary.
|
ImmutableMap |
getAll(Iterable
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.
|
cleanUp, get, getAllPresent, getIfPresent, invalidate, invalidateAll, invalidateAll, put, putAll, size, statsV get(K key) throws ExecutionException
key in this cache, first loading that value if necessary. No observable state associated with this cache is modified until loading completes.
If another call to get(K) or getUnchecked(K) is currently loading the value for key, simply waits for that thread to finish and returns its loaded value. Note that multiple threads can concurrently load values for distinct keys.
Caches loaded by a CacheLoader will call CacheLoader to load new values into the cache. Newly loaded values are added to the cache using Cache.asMap().putIfAbsent after loading has completed; if another value was associated with key while the new value was loading then a removal notification will be sent for the new value.
If the cache loader associated with this cache is known not to throw checked exceptions, then prefer getUnchecked(K) over this method.
ExecutionException - if a checked exception was thrown while loading the value. (
ExecutionException is thrown
even if computation was interrupted by an InterruptedException.)
UncheckedExecutionException - if an unchecked exception was thrown while loading the value
ExecutionError - if an error was thrown while loading the value
V getUnchecked(K key)
key in this cache, first loading that value if necessary. No observable state associated with this cache is modified until loading completes. Unlike
get(K), 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.
If another call to get(K) or getUnchecked(K) is currently loading the value for key, simply waits for that thread to finish and returns its loaded value. Note that multiple threads can concurrently load values for distinct keys.
Caches loaded by a CacheLoader will call CacheLoader to load new values into the cache. Newly loaded values are added to the cache using Cache.asMap().putIfAbsent after loading has completed; if another value was associated with key while the new value was loading then a removal notification will be sent for the new value.
Warning: this method silently converts checked exceptions to unchecked exceptions, and should not be used with cache loaders which throw checked exceptions. In such cases use get(K) instead.
UncheckedExecutionException - if an exception was thrown while loading the value. (As explained in the last paragraph above, this should be an unchecked exception only.)
ExecutionError - if an error was thrown while loading the value
ImmutableMap<K ,V> getAll(Iterable <? extends K> keys) throws ExecutionException
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 for all keys which are not already present in the cache. All entries returned by CacheLoader will be stored in the cache, over-writing any previously cached values. This method will throw an exception if CacheLoader 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, will be ignored.
ExecutionException - if a checked exception was thrown while loading the value. (
ExecutionException is thrown
even if computation was interrupted by an InterruptedException.)
UncheckedExecutionException - if an unchecked exception was thrown while loading the values
ExecutionError - if an error was thrown while loading the values
@Deprecated V apply(K key)
Function interface; use get(K) or getUnchecked(K) instead.
Function
input. This method is
generally expected, but not absolutely required, to have the following properties:
Objects.equal(a, b) implies that Objects.equal(function.apply(a), function.apply(b)). apply in interface
Function<K,V>
UncheckedExecutionException - if an exception was thrown while loading the value. (As described in the documentation for
getUnchecked(K),
LoadingCache should be used as a
Function only with cache loaders that throw only unchecked exceptions.)
void refresh(K 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 if the cache currently contains a value for key, and CacheLoader otherwise. Loading is asynchronous only if CacheLoader was overridden with an asynchronous implementation.
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.
ConcurrentMap<K ,V> asMap()
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.
Note that although the view is modifiable, no method on the returned map will ever cause entries to be automatically loaded.