org.springframework.cache

Interface Cache

All Known Implementing Classes:

AbstractValueAdaptingCache, ConcurrentMapCache, NoOpCache

public interface Cache

Interface that defines common cache operations. Note: Due to the generic use of caching, it is recommended that implementations allow storage of null values (for example to cache methods that return null).

Since:

3.1

Author:

Costin Leau, Juergen Hoeller, Stephane Nicoll

Nested Class Summary

Nested Classes

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.

Method Summary

Modifier and Type	Method and Description
void	clear() Remove all mappings from the cache.
void	evict(java.lang.Object key) Evict the mapping for this key from this cache if it is present.
Cache.ValueWrapper	get(java.lang.Object key) Return the value to which this cache maps the specified key.
<T> T	get(java.lang.Object key, java.util.concurrent.Callable<T> valueLoader) Return the value to which this cache maps the specified key, obtaining that value from valueLoader if necessary.
<T> T	get(java.lang.Object key, java.lang.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.
java.lang.String	getName() Return the cache name.
java.lang.Object	getNativeCache() Return the underlying native cache provider.
void	put(java.lang.Object key, java.lang.Object value) Associate the specified value with the specified key in this cache.
Cache.ValueWrapper	putIfAbsent(java.lang.Object key, java.lang.Object value) Atomically associate the specified value with the specified key in this cache if it is not set already.

Method Detail

getName

java.lang.String getName()

Return the cache name.

getNativeCache

java.lang.Object getNativeCache()

Return the underlying native cache provider.

get

@Nullable
Cache.ValueWrapper get(java.lang.Object key)

Return the value to which this cache maps the specified 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.

Parameters:

key - the key whose associated value is to be returned

Returns:

the value to which this cache maps the specified key, contained within a Cache.ValueWrapper which may also hold a cached null value. A straight null being returned means that the cache contains no mapping for this key.

See Also:

get(Object, Class)

get

@Nullable
<T> T get(java.lang.Object key,
                    @Nullable
                    java.lang.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.

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.

Parameters:

key - the key whose associated value is to be returned

type - 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)

Returns:

the value to which this cache maps the specified key (which may be null itself), or also null if the cache contains no mapping for this key

Throws:

java.lang.IllegalStateException - if a cache entry has been found but failed to match the specified type

Since:

4.0

See Also:

get(Object)

get

@Nullable
<T> T get(java.lang.Object key,
                    java.util.concurrent.Callable<T> valueLoader)

Return the value to which this cache maps the specified key, obtaining that value from 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

Parameters:

key - the key whose associated value is to be returned

Returns:

the value to which this cache maps the specified key

Throws:

Cache.ValueRetrievalException - if the valueLoader throws an exception

Since:

4.3

put

void put(java.lang.Object key,
         @Nullable
         java.lang.Object value)

Associate the specified value with the specified key in this cache.

If the cache previously contained a mapping for this key, the old value is replaced by the specified value.

Parameters:

key - the key with which the specified value is to be associated

value - the value to be associated with the specified key

putIfAbsent

@Nullable
Cache.ValueWrapper putIfAbsent(java.lang.Object key,
                                         @Nullable
                                         java.lang.Object value)

Atomically associate the specified value with the specified key in this cache if it is not set already.

This is equivalent to:

 Object existingValue = cache.get(key);
 if (existingValue == null) {
     cache.put(key, value);
     return null;
 } else {
     return existingValue;
 }
 

except that the action is performed atomically. While all out-of-the-box 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.

Parameters:

key - the key with which the specified value is to be associated

value - the value to be associated with the specified key

Returns:

the value to which this cache maps the specified key (which may be null 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.

Since:

4.1

evict

void evict(java.lang.Object key)

Evict the mapping for this key from this cache if it is present.

Parameters:

key - the key whose mapping is to be removed from the cache

clear

void clear()

Remove all mappings from the cache.