org.springframework.cache.support

Class AbstractValueAdaptingCache

java.lang.Object

org.springframework.cache.support.AbstractValueAdaptingCache

All Implemented Interfaces:

Cache

Direct Known Subclasses:

CaffeineCache, ConcurrentMapCache, JCacheCache

public abstract class AbstractValueAdaptingCache
extends Object
implements Cache

Common base class for Cache implementations that need to adapt null values (and potentially other such special values) before passing them on to the underlying store.

Transparently replaces given null user values with an internal NullValue.INSTANCE, if configured to support null values (as indicated by isAllowNullValues().

Since:

4.2.2

Author:

Juergen Hoeller

Nested Class Summary

Nested classes/interfaces inherited from interface org.springframework.cache.Cache

Cache.ValueRetrievalException, Cache.ValueWrapper

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AbstractValueAdaptingCache(boolean allowNullValues) Create an AbstractValueAdaptingCache with the given setting.

Method Summary

Modifier and Type	Method and Description
protected Object	fromStoreValue(Object storeValue) Convert the given value from the internal store to a user value returned from the get method (adapting null).
Cache.ValueWrapper	get(Object key) Return the value to which this cache maps the specified key.
<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.
boolean	isAllowNullValues() Return whether null values are allowed in this cache.
protected abstract Object	lookup(Object key) Perform an actual lookup in the underlying store.
protected Object	toStoreValue(Object userValue) Convert the given user value, as passed into the put method, to a value in the internal store (adapting null).
protected Cache.ValueWrapper	toValueWrapper(Object storeValue) Wrap the given store value with a SimpleValueWrapper, also going through fromStoreValue(java.lang.Object) conversion.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.springframework.cache.Cache

clear, evict, get, getName, getNativeCache, put, putIfAbsent

Constructor Detail

AbstractValueAdaptingCache

protected AbstractValueAdaptingCache(boolean allowNullValues)

Create an AbstractValueAdaptingCache with the given setting.

Parameters:

allowNullValues - whether to allow for null values

Method Detail

isAllowNullValues

public final boolean isAllowNullValues()

Return whether null values are allowed in this cache.

get

@Nullable
public Cache.ValueWrapper get(Object key)

Description copied from interface: Cache

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.

Specified by:

get in interface Cache

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:

Cache.get(Object, Class), Cache.get(Object, Callable)

get

@Nullable
public <T> T get(Object key,
                           @Nullable
                           Class<T> type)

Description copied from interface: Cache

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 Cache.get(Object) variant for that purpose instead.

Specified by:

get in interface Cache

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

See Also:

Cache.get(Object)

lookup

@Nullable
protected abstract Object lookup(Object key)

Perform an actual lookup in the underlying store.

Parameters:

key - the key whose associated value is to be returned

Returns:

the raw store value for the key, or null if none

fromStoreValue

@Nullable
protected Object fromStoreValue(@Nullable
                                          Object storeValue)

Convert the given value from the internal store to a user value returned from the get method (adapting null).

Parameters:

storeValue - the store value

Returns:

the value to return to the user

toStoreValue

protected Object toStoreValue(@Nullable
                              Object userValue)

Convert the given user value, as passed into the put method, to a value in the internal store (adapting null).

Parameters:

userValue - the given user value

Returns:

the value to store

toValueWrapper

@Nullable
protected Cache.ValueWrapper toValueWrapper(@Nullable
                                                      Object storeValue)

Wrap the given store value with a SimpleValueWrapper, also going through fromStoreValue(java.lang.Object) conversion. Useful for get(Object) and Cache.putIfAbsent(Object, Object) implementations.

Parameters:

storeValue - the original value

Returns:

the wrapped value