public interface Cache
null values (for example to
cache methods that return null).| Modifier and Type | Interface and Description |
|---|---|
static class |
Cache.ValueRetrievalException
Wrapper exception to be thrown from
get(Object, Callable)
in case of the value loader callback failing with an exception. |
static interface |
Cache.ValueWrapper
A (wrapper) object representing a cache value.
|
| Modifier and Type | Method and Description |
|---|---|
void |
clear()
Clear the cache through removing all mappings.
|
void |
evict(Object key)
Evict the mapping for this key from this cache if it is present.
|
default boolean |
evictIfPresent(Object key)
Evict the mapping for this key from this cache if it is present,
expecting the key to be immediately invisible for subsequent lookups.
|
Cache.ValueWrapper |
get(Object key)
Return the value to which this cache maps the specified key.
|
<T> T |
get(Object key,
Callable<T> valueLoader)
Return the value to which this cache maps the specified key, obtaining
that value from
valueLoader if necessary. |
<T> T |
get(Object key,
Class<T> type)
Return the value to which this cache maps the specified key,
generically specifying a type that return value will be cast to.
|
String |
getName()
Return the cache name.
|
Object |
getNativeCache()
Return the underlying native cache provider.
|
default boolean |
invalidate()
Invalidate the cache through removing all mappings, expecting all
entries to be immediately invisible for subsequent lookups.
|
void |
put(Object key,
Object value)
Associate the specified value with the specified key in this cache.
|
default Cache.ValueWrapper |
putIfAbsent(Object key,
Object value)
Atomically associate the specified value with the specified key in this cache
if it is not set already.
|
String getName()
Object getNativeCache()
@Nullable Cache.ValueWrapper get(Object key)
Returns null if the cache contains no mapping for this key;
otherwise, the cached value (which may be null itself) will
be returned in a Cache.ValueWrapper.
key - the key whose associated value is to be returnedCache.ValueWrapper which may also hold
a cached null value. A straight null being
returned means that the cache contains no mapping for this key.get(Object, Class),
get(Object, Callable)@Nullable <T> T get(Object key, @Nullable Class<T> type)
Note: This variant of get does not allow for differentiating
between a cached null value and no cache entry found at all.
Use the standard get(Object) variant for that purpose instead.
key - the key whose associated value is to be returnedtype - the required type of the returned value (may be
null to bypass a type check; in case of a null
value found in the cache, the specified type is irrelevant)null itself), or also null if
the cache contains no mapping for this keyIllegalStateException - if a cache entry has been found
but failed to match the specified typeget(Object)@Nullable <T> T get(Object key, Callable<T> valueLoader)
valueLoader if necessary. This method provides
a simple substitute for the conventional "if cached, return; otherwise
create, cache and return" pattern.
If possible, implementations should ensure that the loading operation
is synchronized so that the specified valueLoader is only called
once in case of concurrent access on the same key.
If the valueLoader throws an exception, it is wrapped in
a Cache.ValueRetrievalException
key - the key whose associated value is to be returnedCache.ValueRetrievalException - if the valueLoader throws an exceptionget(Object)void put(Object key, @Nullable Object value)
If the cache previously contained a mapping for this key, the old value is replaced by the specified value.
Actual registration may be performed in an asynchronous or deferred
fashion, with subsequent lookups possibly not seeing the entry yet.
This may for example be the case with transactional cache decorators.
Use putIfAbsent(java.lang.Object, java.lang.Object) for guaranteed immediate registration.
key - the key with which the specified value is to be associatedvalue - the value to be associated with the specified keyputIfAbsent(Object, Object)@Nullable default Cache.ValueWrapper putIfAbsent(Object key, @Nullable Object value)
This is equivalent to:
ValueWrapper existingValue = cache.get(key);
if (existingValue == null) {
cache.put(key, value);
}
return existingValue;
CacheManager implementations are able to perform the put atomically,
the operation may also be implemented in two steps, e.g. with a check for
presence and a subsequent put, in a non-atomic way. Check the documentation
of the native cache implementation that you are using for more details.
The default implementation delegates to get(Object) and
put(Object, Object) along the lines of the code snippet above.
key - the key with which the specified value is to be associatedvalue - the value to be associated with the specified keynull itself), or also null if the cache did not contain any
mapping for that key prior to this call. Returning null is therefore
an indicator that the given value has been associated with the key.put(Object, Object)void evict(Object key)
Actual eviction may be performed in an asynchronous or deferred
fashion, with subsequent lookups possibly still seeing the entry.
This may for example be the case with transactional cache decorators.
Use evictIfPresent(java.lang.Object) for guaranteed immediate removal.
key - the key whose mapping is to be removed from the cacheevictIfPresent(Object)default boolean evictIfPresent(Object key)
The default implementation delegates to evict(Object),
returning false for not-determined prior presence of the key.
Cache providers and in particular cache decorators are encouraged
to perform immediate eviction if possible (e.g. in case of generally
deferred cache operations within a transaction) and to reliably
determine prior presence of the given key.
key - the key whose mapping is to be removed from the cachetrue if the cache was known to have a mapping for
this key before, false if it did not (or if prior presence
could not be determined)evict(Object)void clear()
Actual clearing may be performed in an asynchronous or deferred
fashion, with subsequent lookups possibly still seeing the entries.
This may for example be the case with transactional cache decorators.
Use invalidate() for guaranteed immediate removal of entries.
invalidate()default boolean invalidate()
true if the cache was known to have mappings before,
false if it did not (or if prior presence of entries could
not be determined)clear()