Package 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>, 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.

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:

  • Constructor Details

    • LRUMap

      public LRUMap(int initialEntries, int maxEntries)

  • Method Details

    • 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(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(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.