Package edu.internet2.middleware.grouperClientExt.com.fasterxml.jackson.databind.util

Class LRUMap<K,V>

java.lang.Object
edu.internet2.middleware.grouperClientExt.com.fasterxml.jackson.databind.util.LRUMap<K,V>
All Implemented Interfaces:
LookupCache<K,V>, Serializable
public class LRUMap<K,V> extends Object implements LookupCache<K,V>, 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. Plan from Jackson 2.12 is to focus more on pluggability as LookupCache and let users, frameworks, provide their own cache implementations.

See Also:

  • Field Details

    • _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 Details

    • LRUMap

      public LRUMap(int initialEntries, int maxEntries)

  • Method Details

    • 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(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

    • readResolve

      protected Object readResolve()