org.springframework.util
Class CachingMapDecorator

java.lang.Object
  org.springframework.util.CachingMapDecorator

All Implemented Interfaces:

Serializable, Map

public class CachingMapDecorator
extends Object
implements Map, 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 also 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>

Field Summary

protected static Object

NULL_VALUE

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 targetMap)
Create a CachingMapDecorator for the given Map.

CachingMapDecorator(Map 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 Object	create(Object key) Create a value to cache for the given key.
Set	entrySet()
Object	get(Object key) Get value for key.
boolean	isEmpty()
Set	keySet()
Object	put(Object key, Object value) Put an object into the cache, possibly wrapping it with a weak reference.
void	putAll(Map map)
Object	remove(Object key)
int	size()
String	toString()
protected boolean	useWeakValue(Object key, Object value) Decide whether use a weak reference for the value of the given key-value pair.
Collection	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

Field Detail

NULL_VALUE

protected static Object NULL_VALUE

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 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 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

isEmpty

public boolean isEmpty()

Specified by:

isEmpty in interface Map

containsKey

public boolean containsKey(Object key)

Specified by:

containsKey in interface Map

containsValue

public boolean containsValue(Object value)

Specified by:

containsValue in interface Map

remove

public Object remove(Object key)

Specified by:

remove in interface Map

putAll

public void putAll(Map map)

Specified by:

putAll in interface Map

clear

public void clear()

Specified by:

clear in interface Map

keySet

public Set keySet()

Specified by:

keySet in interface Map

values

public Collection values()

Specified by:

values in interface Map

entrySet

public Set entrySet()

Specified by:

entrySet in interface Map

put

public Object put(Object key,
                  Object value)

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

Specified by:

put in interface Map

See Also:

useWeakValue(Object, Object)

useWeakValue

protected boolean useWeakValue(Object key,
                               Object value)

Decide whether 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 Object 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

See Also:

create(Object)

create

protected Object create(Object 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