com.fasterxml.jackson.databind.util

Class LRUMap<K,V>

java.lang.Object

java.util.AbstractMap<K,V>

java.util.HashMap<K,V>

java.util.LinkedHashMap<K,V>

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

All Implemented Interfaces:

Serializable, Cloneable, Map<K,V>

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

Helper for simple bounded LRU 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: the only reason we extend LinkedHashMap instead of aggregating it is that this way we can override removeEldestEntry(java.util.Map.Entry<K, V>). Access, however, MUST be done using single-element access methods (or matching xxxAll() methods that call them); access via iterators are not guaranteed to work.

NOTE: since version 2.4, uses ReentrantReadWriteLock to improve concurrent access.

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class java.util.AbstractMap

AbstractMap.SimpleEntry<K,V>, AbstractMap.SimpleImmutableEntry<K,V>

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 int	_maxEntries
protected Lock	_readLock
protected Lock	_writeLock

Constructor Summary

Constructors

Constructor and Description
LRUMap(int initialEntries, int maxEntries)

Method Summary

Methods

Modifier and Type	Method and Description
V	get(Object key)
V	put(K key, V value)
protected Object	readResolve()
V	remove(Object key)
protected boolean	removeEldestEntry(Map.Entry<K,V> eldest)

Methods inherited from class java.util.LinkedHashMap

clear, containsValue

Methods inherited from class java.util.HashMap

clone, containsKey, entrySet, isEmpty, keySet, putAll, size, values

Methods inherited from class java.util.AbstractMap

equals, hashCode, toString

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Map

containsKey, entrySet, equals, hashCode, isEmpty, keySet, putAll, size, values

Field Detail

_readLock

protected final transient Lock _readLock

_writeLock

protected final transient Lock _writeLock

_maxEntries

protected final transient int _maxEntries

_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

removeEldestEntry

protected boolean removeEldestEntry(Map.Entry<K,V> eldest)

Overrides:

removeEldestEntry in class LinkedHashMap<K,V>

get

public V get(Object key)

Specified by:

get in interface Map<K,V>

Overrides:

get in class LinkedHashMap<K,V>

put

public V put(K key,
    V value)

Specified by:

put in interface Map<K,V>

Overrides:

put in class HashMap<K,V>

remove

public V remove(Object key)

Specified by:

remove in interface Map<K,V>

Overrides:

remove in class HashMap<K,V>

readResolve

protected Object readResolve()