Package org.apache.struts2.inject.util

Class ReferenceCache<K,V>

java.lang.Object

org.apache.struts2.inject.util.ReferenceMap<K,V>

org.apache.struts2.inject.util.ReferenceCache<K,V>

All Implemented Interfaces:

Serializable, Map<K,V>

public abstract class ReferenceCache<K,V>
extends ReferenceMap<K,V>

Extends ReferenceMap to support lazy loading values by overriding create(Object).

Author:

crazybob@google.com (Bob Lee)

See Also:

• Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.struts2.inject.util.ReferenceMap

ReferenceMap.Strategy

Constructor Summary

Constructors

Constructor	Description
ReferenceCache()	Equivalent to new ReferenceCache(STRONG, STRONG).
ReferenceCache(ReferenceType keyReferenceType, ReferenceType valueReferenceType)

Method Summary

Modifier and Type	Method	Description
protected void	cancel()	Cancels the current create(Object).
protected abstract V	create(K key)	Override to lazy load values.
V	get(Object key)
static <K, V> ReferenceCache<K,V>	of(ReferenceType keyReferenceType, ReferenceType valueReferenceType, Function<? super K,? extends V> function)	Returns a ReferenceCache delegating to the specified function.

Methods inherited from class org.apache.struts2.inject.util.ReferenceMap

clear, containsKey, containsValue, entrySet, getPutStrategy, isEmpty, keySet, put, putAll, putIfAbsent, putIfAbsentStrategy, putStrategy, remove, remove, replace, replace, replaceStrategy, size, values

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Map

compute, computeIfAbsent, computeIfPresent, equals, forEach, getOrDefault, hashCode, merge, replaceAll

Constructor Details

ReferenceCache

public ReferenceCache(ReferenceType keyReferenceType,
 ReferenceType valueReferenceType)

ReferenceCache

public ReferenceCache()

Equivalent to new ReferenceCache(STRONG, STRONG).

Method Details

create

protected abstract V create(K key)

Override to lazy load values. Use as an alternative to ReferenceMap.put(Object, Object). Invoked by getter if value isn't already cached. Must not return null. This method will not be called again until the garbage collector reclaims the returned value.

Parameters:

key - the key

Returns:

returned value

get

public V get(Object key)

If this map does not contain an entry for the given key and create(Object) has been overridden, this method will create a new value, put it in the map, and return it.

Specified by:

get in interface Map<K,V>

Overrides:

get in class ReferenceMap<K,V>

Parameters:

key - the key

Returns:

return new created value

Throws:

NullPointerException - if create(Object) returns null.

CancellationException - if the creation is cancelled. See cancel().

cancel

protected void cancel()

Cancels the current create(Object). Throws CancellationException to all clients currently blocked on get(Object).

of

public static <K,
V> ReferenceCache<K,V> of(ReferenceType keyReferenceType,
 ReferenceType valueReferenceType,
 Function<? super K,? extends V> function)

Returns a ReferenceCache delegating to the specified function. The specified function must not return null.

Type Parameters:

K - type of key

V - type of value

Parameters:

function - function

keyReferenceType - key reference type

valueReferenceType - value reference type

Returns:

reference cache