org.springframework.util
Class CachingMapDecorator<K,V>

java.lang.Object
  org.springframework.util.CachingMapDecorator<K,V>

All Implemented Interfaces:

Serializable, Map<K,V>

public abstract class CachingMapDecorator<K,V>
extends Object
implements Map<K,V>, Serializable

A simple decorator for a Map, encapsulating the workflow for caching expensive values in a target Map. Supports caching weak or strong keys.

This class is an abstract template. Caching Map implementations should subclass and override the create(key) method which encapsulates expensive creation of a new object.

Since:

1.2.2

Author:

Keith Donald, Juergen Hoeller

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from interface java.util.Map

Map.Entry<K,V>

Constructor Summary

CachingMapDecorator()
Create a CachingMapDecorator with strong keys, using an underlying synchronized Map.

CachingMapDecorator(boolean weak)
Create a CachingMapDecorator, using an underlying synchronized Map.

CachingMapDecorator(boolean weak, int size)
Create a CachingMapDecorator with initial size, using an underlying synchronized Map.

CachingMapDecorator(Map<K,V> targetMap)
Create a CachingMapDecorator for the given Map.

CachingMapDecorator(Map<K,V> targetMap, boolean synchronize, boolean weak)
Create a CachingMapDecorator for the given Map.

Method Summary

void	clear()
boolean	containsKey(Object key)
boolean	containsValue(Object value)
protected abstract V	create(K key) Create a value to cache for the given key.
Set<Map.Entry<K,V>>	entrySet()
V	get(Object key) Get value for key.
boolean	isEmpty()
Set<K>	keySet()
V	put(K key, V value) Put an object into the cache, possibly wrapping it with a weak reference.
void	putAll(Map<? extends K,? extends V> map)
V	remove(Object key)
int	size()
String	toString()
protected boolean	useWeakValue(K key, V value) Decide whether to use a weak reference for the value of the given key-value pair.
Collection<V>	values()

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Map

equals, hashCode

Constructor Detail

CachingMapDecorator

public CachingMapDecorator()

Create a CachingMapDecorator with strong keys, using an underlying synchronized Map.

CachingMapDecorator

public CachingMapDecorator(boolean weak)

Create a CachingMapDecorator, using an underlying synchronized Map.

Parameters:

weak - whether to use weak references for keys and values

CachingMapDecorator

public CachingMapDecorator(boolean weak,
                           int size)

Create a CachingMapDecorator with initial size, using an underlying synchronized Map.

Parameters:

weak - whether to use weak references for keys and values

size - the initial cache size

CachingMapDecorator

public CachingMapDecorator(Map<K,V> targetMap)

Create a CachingMapDecorator for the given Map.

The passed-in Map won't get synchronized explicitly, so make sure to pass in a properly synchronized Map, if desired.

Parameters:

targetMap - the Map to decorate

CachingMapDecorator

public CachingMapDecorator(Map<K,V> targetMap,
                           boolean synchronize,
                           boolean weak)

Create a CachingMapDecorator for the given Map.

The passed-in Map won't get synchronized explicitly unless you specify "synchronize" as "true".

Parameters:

targetMap - the Map to decorate

synchronize - whether to synchronize on the given Map

weak - whether to use weak references for values

Method Detail

size

public int size()

Specified by:

size in interface Map<K,V>

isEmpty

public boolean isEmpty()

Specified by:

isEmpty in interface Map<K,V>

containsKey

public boolean containsKey(Object key)

Specified by:

containsKey in interface Map<K,V>

containsValue

public boolean containsValue(Object value)

Specified by:

containsValue in interface Map<K,V>

remove

public V remove(Object key)

Specified by:

remove in interface Map<K,V>

putAll

public void putAll(Map<? extends K,? extends V> map)

Specified by:

putAll in interface Map<K,V>

clear

public void clear()

Specified by:

clear in interface Map<K,V>

keySet

public Set<K> keySet()

Specified by:

keySet in interface Map<K,V>

values

public Collection<V> values()

Specified by:

values in interface Map<K,V>

entrySet

public Set<Map.Entry<K,V>> entrySet()

Specified by:

entrySet in interface Map<K,V>

put

public V put(K key,
             V value)

Put an object into the cache, possibly wrapping it with a weak reference.

Specified by:

put in interface Map<K,V>

See Also:

useWeakValue(Object, Object)

useWeakValue

protected boolean useWeakValue(K key,
                               V value)

Decide whether to use a weak reference for the value of the given key-value pair.

Parameters:

key - the candidate key

value - the candidate value

Returns:

true in order to use a weak reference; false otherwise.

get

public V get(Object key)

Get value for key. Creates and caches value if it doesn't already exist in the cache.

This implementation is not synchronized: This is highly concurrent but does not guarantee unique instances in the cache, as multiple values for the same key could get created in parallel. Consider overriding this method to synchronize it, if desired.

Specified by:

get in interface Map<K,V>

See Also:

create(Object)

create

protected abstract V create(K key)

Create a value to cache for the given key. Called by get if there is no value cached already.

Parameters:

key - the cache key

See Also:

get(Object)

toString

public String toString()

Overrides:

toString in class Object