com.fasterxml.jackson.databind.util

Class LRUMap<K,V>

java.lang.Object

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

All Implemented Interfaces:

LookupCache<K,V>, java.io.Serializable

public class LRUMap<K,V>
extends java.lang.Object
implements LookupCache<K,V>, java.io.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.

Since Jackson 2.12, there has been pluggable LookupCache interface which allows users, frameworks, provide their own cache implementations.

Since Jackson 2.14, the implementation

• Evicts the least recently used entry when max size is reached
• Is thread-safe and does NOT require external synchronization

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
LRUMap(int initialEntries, int maxEntries)

Method Summary

Modifier and Type	Method and Description
void	clear() Method for removing all contents this cache has.
void	contents(java.util.function.BiConsumer<K,V> consumer) Method to apply operation on cache contents without exposing them.
LookupCache<K,V>	emptyCopy() Method needed for creating clones but without contents.
V	get(java.lang.Object key) NOTE: key is of type Object only to retain binary backwards-compatibility
V	put(K key, V value)
V	putIfAbsent(K key, V value)
int	size()

Methods inherited from class java.lang.Object

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

Constructor Detail

LRUMap

public LRUMap(int initialEntries,
              int maxEntries)

Method Detail

emptyCopy

public LookupCache<K,V> emptyCopy()

Description copied from interface: LookupCache

Method needed for creating clones but without contents.

Default implementation throws UnsupportedOperationException. Implementations are required to override this method.

Specified by:

emptyCopy in interface LookupCache<K,V>

put

public V put(K key,
             V value)

Specified by:

put in interface LookupCache<K,V>

putIfAbsent

public V putIfAbsent(K key,
                     V value)

Specified by:

putIfAbsent in interface LookupCache<K,V>

Since:

2.5

get

public V get(java.lang.Object key)

Description copied from interface: LookupCache

NOTE: key is of type Object only to retain binary backwards-compatibility

Specified by:

get in interface LookupCache<K,V>

Returns:

value associated with key (can return null)

clear

public void clear()

Description copied from interface: LookupCache

Method for removing all contents this cache has.

Specified by:

clear in interface LookupCache<K,V>

size

public int size()

Specified by:

size in interface LookupCache<K,V>

Returns:

Number of entries currently in cache: may be approximate, only to be used for diagnostics, metrics reporting

contents

public void contents(java.util.function.BiConsumer<K,V> consumer)

Description copied from interface: LookupCache

Method to apply operation on cache contents without exposing them.

Default implementation throws UnsupportedOperationException. Implementations are required to override this method.

Specified by:

contents in interface LookupCache<K,V>

Parameters:

consumer - Operation to apply on cache contents.