Package org.jivesoftware.util.cache

Class DefaultCache<K extends Serializable,V extends Serializable>

java.lang.Object
org.jivesoftware.util.cache.DefaultCache<K,V>
All Implemented Interfaces:
Map<K,V>, Cache<K,V>
public class DefaultCache<K extends Serializable,V extends Serializable> extends Object implements Cache<K,V>
Default, non-distributed implementation of the Cache interface. The algorithm for cache is as follows: a HashMap is maintained for fast object lookup. Two linked lists are maintained: one keeps objects in the order they are accessed from cache, the other keeps objects in the order they were originally added to cache. When objects are added to cache, they are first wrapped by a CacheObject which maintains the following pieces of information:
  • The size of the object (in bytes).
  • A pointer to the node in the linked list that maintains accessed order for the object. Keeping a reference to the node lets us avoid linear scans of the linked list.
  • A pointer to the node in the linked list that maintains the age of the object in cache. Keeping a reference to the node lets us avoid linear scans of the linked list.

To get an object from cache, a hash lookup is performed to get a reference to the CacheObject that wraps the real object we are looking for. The object is subsequently moved to the front of the accessed linked list and any necessary cache cleanups are performed. Cache deletion and expiration is performed as needed.

Author:
Matt Tucker

  • Field Details

    • NULL_KEY_IS_NOT_ALLOWED

      protected static final String NULL_KEY_IS_NOT_ALLOWED
      See Also:

    • NULL_VALUE_IS_NOT_ALLOWED

      protected static final String NULL_VALUE_IS_NOT_ALLOWED
      See Also:

    • allowNull

      protected static final boolean allowNull

    • MAX_CULL_COUNT_PERIOD

      protected static final long MAX_CULL_COUNT_PERIOD

    • map

      protected Map<K extends Serializable,org.jivesoftware.util.cache.DefaultCache.CacheObject<V extends Serializable>> map
      The map the keys and values are stored in.

  • Method Details

    • put

      public V put(K key, V value)
      Specified by:
      put in interface Map<K extends Serializable,V extends Serializable>

    • get

      public V get(Object key)
      Specified by:
      get in interface Map<K extends Serializable,V extends Serializable>

    • remove

      public V remove(Object key)
      Specified by:
      remove in interface Map<K extends Serializable,V extends Serializable>

    • clear

      public void clear()
      Specified by:
      clear in interface Map<K extends Serializable,V extends Serializable>

    • size

      public int size()
      Specified by:
      size in interface Map<K extends Serializable,V extends Serializable>

    • isEmpty

      public boolean isEmpty()
      Specified by:
      isEmpty in interface Map<K extends Serializable,V extends Serializable>

    • values

      @Nonnull public Collection<V> values()
      Description copied from interface: Cache
      IMPORTANT: Unlike the standard Map.values() implementation, the collection returned from this method cannot be modified.
      Specified by:
      values in interface Cache<K extends Serializable,V extends Serializable>
      Specified by:
      values in interface Map<K extends Serializable,V extends Serializable>
      Returns:
      an unmodifiable collection view of the values contained in this map

    • containsKey

      public boolean containsKey(Object key)
      Specified by:
      containsKey in interface Map<K extends Serializable,V extends Serializable>

    • putAll

      public void putAll(Map<? extends K,? extends V> map)
      Specified by:
      putAll in interface Map<K extends Serializable,V extends Serializable>

    • containsValue

      public boolean containsValue(Object value)
      Specified by:
      containsValue in interface Map<K extends Serializable,V extends Serializable>

    • entrySet

      @Nonnull public Set<Map.Entry<K,V>> entrySet()
      Description copied from interface: Cache
      IMPORTANT: Unlike the standard Map.entrySet() implementation, the set returned from this method cannot be modified.
      Specified by:
      entrySet in interface Cache<K extends Serializable,V extends Serializable>
      Specified by:
      entrySet in interface Map<K extends Serializable,V extends Serializable>
      Returns:
      an unmodifiable set view of the mappings contained in this map

    • keySet

      @Nonnull public Set<K> keySet()
      Description copied from interface: Cache
      IMPORTANT: Unlike the standard Map.keySet() implementation, the set returned from this method cannot be modified.
      Specified by:
      keySet in interface Cache<K extends Serializable,V extends Serializable>
      Specified by:
      keySet in interface Map<K extends Serializable,V extends Serializable>
      Returns:
      an unmodifiable set view of the keys contained in this map

    • getLock

      @Nonnull public Lock getLock(K key)
      Description copied from interface: Cache
      Returns an existing Lock on the specified key or creates a new one if none was found. This operation is thread safe. Successive calls with the same key may or may not return the same Lock. However, different threads asking for the same Lock at the same time will get the same Lock object.

      The supplied cache may or may not be used depending whether the server is running on cluster mode or not. When not running as part of a cluster then the lock will be unrelated to the cache and will only be visible in this JVM.

      Specified by:
      getLock in interface Cache<K extends Serializable,V extends Serializable>
      Parameters:
      key - the object that defines the visibility or scope of the lock.
      Returns:
      an existing lock on the specified key or creates a new one if none was found.

    • getCapacityUnit

      public Cache.CapacityUnit getCapacityUnit()
      Defines the unit used to calculate the capacity of the cache, which for all instances of this class is byte-size based.
      Specified by:
      getCapacityUnit in interface Cache<K extends Serializable,V extends Serializable>
      Returns:
      the unit to be used to calculate the capacity of this cache, which will be Cache.CapacityUnit.BYTES.

    • getName

      public String getName()
      Returns the name of this cache. The name is completely arbitrary and used only for display to administrators.
      Specified by:
      getName in interface Cache<K extends Serializable,V extends Serializable>
      Returns:
      the name of this cache.

    • setName

      public void setName(String name)
      Sets the name of this cache.
      Specified by:
      setName in interface Cache<K extends Serializable,V extends Serializable>
      Parameters:
      name - the name of this cache.

    • getCacheHits

      public long getCacheHits()
      Returns the number of cache hits. A cache hit occurs every time the get method is called and the cache contains the requested object.

      Keeping track of cache hits and misses lets one measure how efficient the cache is; the higher the percentage of hits, the more efficient.

      Specified by:
      getCacheHits in interface Cache<K extends Serializable,V extends Serializable>
      Returns:
      the number of cache hits.

    • getCacheMisses

      public long getCacheMisses()
      Returns the number of cache misses. A cache miss occurs every time the get method is called and the cache does not contain the requested object.

      Keeping track of cache hits and misses lets one measure how efficient the cache is; the higher the percentage of hits, the more efficient.

      Specified by:
      getCacheMisses in interface Cache<K extends Serializable,V extends Serializable>
      Returns:
      the number of cache hits.

    • getLongCacheSize

      public long getLongCacheSize()
      Returns the size of the cache contents in bytes. This value is only a rough approximation, so cache users should expect that actual VM memory used by the cache could be significantly higher than the value reported by this method.
      Specified by:
      getLongCacheSize in interface Cache<K extends Serializable,V extends Serializable>
      Returns:
      the size of the cache contents in bytes.

    • getMaxCacheSize

      public long getMaxCacheSize()
      Returns the maximum size of the cache (in bytes). If the cache grows larger than the max size, the least frequently used items will be removed. If the max cache size is set to -1, there is no size limit.
      Specified by:
      getMaxCacheSize in interface Cache<K extends Serializable,V extends Serializable>
      Returns:
      the maximum size of the cache (-1 indicates unlimited max size).

    • setMaxCacheSize

      public void setMaxCacheSize(long maxSize)
      Sets the maximum size of the cache in bytes. If the cache grows larger than the max size, the least frequently used items will be removed. If the max cache size is set to -1, there is no size limit.

      Note: If using the Hazelcast clustering plugin, this will not take effect until the next time the cache is created

      Specified by:
      setMaxCacheSize in interface Cache<K extends Serializable,V extends Serializable>
      Parameters:
      maxSize - the maximum size of the cache in bytes.

    • getMaxLifetime

      public long getMaxLifetime()
      Returns the maximum number of milliseconds that any object can live in cache. Once the specified number of milliseconds passes, the object will be automatically expired from cache. If the max lifetime is set to -1, then objects never expire.
      Specified by:
      getMaxLifetime in interface Cache<K extends Serializable,V extends Serializable>
      Returns:
      the maximum number of milliseconds before objects are expired.

    • setMaxLifetime

      public void setMaxLifetime(long maxLifetime)
      Sets the maximum number of milliseconds that any object can live in cache. Once the specified number of milliseconds passes, the object will be automatically expired from cache. If the max lifetime is set to -1, then objects never expire.
      Specified by:
      setMaxLifetime in interface Cache<K extends Serializable,V extends Serializable>
      Parameters:
      maxLifetime - the maximum number of milliseconds before objects are expired.

    • getCacheCulls

      public long getCacheCulls(Duration duration)

    • addClusteredCacheEntryListener

      public String addClusteredCacheEntryListener(@Nonnull ClusteredCacheEntryListener<K,V> listener, boolean includeValues, boolean includeEventsFromLocalNode)
      Description copied from interface: Cache
      Registers a listener to receive entry events for this cache. To optimize the amount of data that is being processed, this method allows the listener to be registered in a way that suppresses values from being sent to it. In that case, only keys will be included in the event listener invocation.
      Specified by:
      addClusteredCacheEntryListener in interface Cache<K extends Serializable,V extends Serializable>
      Parameters:
      listener - the listener to be registered.
      includeValues - defines if the listener should receive the values associated with the events.
      includeEventsFromLocalNode - defines if the listener should be invoked for events that originate on the local node.
      Returns:
      a unique identifier for the listener which is used as a key to remove the listener

    • removeClusteredCacheEntryListener

      public void removeClusteredCacheEntryListener(@Nonnull String listenerId)
      Description copied from interface: Cache
      Removes a previously registered event listener.
      Specified by:
      removeClusteredCacheEntryListener in interface Cache<K extends Serializable,V extends Serializable>
      Parameters:
      listenerId - the identifier of the listener to be removed.