com.fasterxml.jackson.databind.util

Class LRUMap<K,V>

java.lang.Object

com.fasterxml.jackson.databind.util.LRUMap<K,V>

All Implemented Interfaces:

Serializable

public class LRUMap<K,V>
extends Object
implements Serializable

Helper for simple bounded maps used for reusing lookup values.

Note that serialization behavior is such that contents are NOT serialized, on assumption that all use cases are for caching where persistence does not make sense. The only thing serialized is the cache size of Map.

NOTE: since version 2.4.2, this is NOT an LRU-based at all; reason being that it is not possible to use JDK components that do LRU _AND_ perform well wrt synchronization on multi-core systems. So we choose efficient synchronization over potentially more efficient handling of entries.

And yes, there are efficient LRU implementations such as concurrentlinkedhashmap; but at this point we really try to keep external deps to minimum. But perhaps a shaded variant may be used one day.

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected int	_jdkSerializeMaxEntries Ugly hack, to work through the requirement that _value is indeed final, and that JDK serialization won't call ctor(s) if Serializable is implemented.
protected ConcurrentHashMap<K,V>	_map
protected int	_maxEntries

Constructor Summary

Constructors

Constructor and Description
LRUMap(int initialEntries, int maxEntries)

Method Summary

Modifier and Type	Method and Description
void	clear()
V	get(Object key)
V	put(K key, V value)
V	putIfAbsent(K key, V value)
protected Object	readResolve()
int	size()

Methods inherited from class java.lang.Object

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

Field Detail

_maxEntries

protected final transient int _maxEntries

_map

protected final transient ConcurrentHashMap<K,V> _map

_jdkSerializeMaxEntries

protected transient int _jdkSerializeMaxEntries

Ugly hack, to work through the requirement that _value is indeed final, and that JDK serialization won't call ctor(s) if Serializable is implemented.

Since:

2.1

Constructor Detail

LRUMap

public LRUMap(int initialEntries,
              int maxEntries)

Method Detail

put

public V put(K key,
             V value)

putIfAbsent

public V putIfAbsent(K key,
                     V value)

Since:

2.5

get

public V get(Object key)

clear

public void clear()

size

public int size()

readResolve

protected Object readResolve()