@Beta @GwtCompatible public abstract class AbstractCache<K,V> extends Object implements Cache<K,V>
Cache interface to minimize the
effort required to implement this interface.
To implement a cache, the programmer needs only to extend this class and provide an
implementation for the put(K, V) and Cache.getIfPresent(java.lang.Object) methods. getAllPresent(java.lang.Iterable<?>) is
implemented in terms of Cache.getIfPresent(java.lang.Object); putAll(java.util.Map<? extends K, ? extends V>) is implemented in terms of
put(K, V), invalidateAll(Iterable) is implemented in terms of invalidate(java.lang.Object).
The method cleanUp() is a no-op. All other methods throw an
UnsupportedOperationException.
| Modifier and Type | Class and Description |
|---|---|
static class |
AbstractCache.SimpleStatsCounter
A thread-safe
AbstractCache.StatsCounter implementation for use by Cache implementors. |
static interface |
AbstractCache.StatsCounter
Accumulates statistics during the operation of a
Cache for presentation by Cache.stats(). |
| Modifier | Constructor and Description |
|---|---|
protected |
AbstractCache()
Constructor for use by subclasses.
|
| Modifier and Type | Method and 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.
|
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)
This implementation of
getAllPresent lacks any insight into the internal cache data
structure, and is thus forced to return the query keys instead of the cached keys. |
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.
|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, waitgetIfPresentprotected AbstractCache()
public V get(K key, Callable<? extends V> valueLoader) throws ExecutionException
Cachekey 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.
get in interface Cache<K,V>ExecutionException - if a checked exception was thrown while loading the valuepublic ImmutableMap<K,V> getAllPresent(Iterable<?> keys)
getAllPresent lacks any insight into the internal cache data
structure, and is thus forced to return the query keys instead of the cached keys. This is only
possible with an unsafe cast which requires keys to actually be of type K.
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.getAllPresent in interface Cache<K,V>public void put(K key, V value)
Cachevalue 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.
public void putAll(Map<? extends K,? extends V> m)
Cacheput(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.public void cleanUp()
Cachepublic long size()
Cachepublic void invalidate(Object key)
Cachekey.invalidate in interface Cache<K,V>public void invalidateAll(Iterable<?> keys)
Cachekeys.invalidateAll in interface Cache<K,V>public void invalidateAll()
CacheinvalidateAll in interface Cache<K,V>public CacheStats stats()
Cachepublic ConcurrentMap<K,V> asMap()
CacheIterators 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.
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