Package org.jivesoftware.util.cache

Interface Cache<K extends Serializable,V extends Serializable>

All Superinterfaces:
Map<K,V>
All Known Implementing Classes:
CacheWrapper, CaffeineCache, ComponentCacheWrapper, DefaultCache, SerializingCache
public interface Cache<K extends Serializable,V extends Serializable> extends Map<K,V>
General purpose cache. It stores objects associated with unique keys in memory for fast access. All keys and values added to the cache must implement the Serializable interface. Values may implement the Cacheable interface, which allows the cache to determine object size much more quickly. These restrictions allow a cache to never grow larger than a specified number of bytes and to optionally be distributed over a cluster of servers.

If the cache does grow too large, objects will be removed such that those that are accessed least frequently are removed first. Because expiration happens automatically, the cache makes no guarantee as to how long an object will remain in cache after it is put in.

Optionally, a maximum lifetime for all objects can be specified. In that case, objects will be deleted from cache after that amount of time, even if they are frequently accessed. This feature is useful if objects put in cache represent data that should be periodically refreshed; for example, information from a database.

All cache operations are thread safe.

Note that neither keys nor values can be null; A NullPointerException will be thrown attempting to place or retrieve null values in to the cache. Caches can (but need not be) used as a mechanism that is used to share data in an Openfire cluster. When a cache is used for this purpose, it is important to realize that, when joining or leaving a cluster, the cache content will be cleared of all data that was added on the local cluster node. Typically, ClusterEventListener is used to detect these events and restore the content of the cache.

See Also:

  • Field Details

  • Method Details

    • getCapacityUnit

      default Cache.CapacityUnit getCapacityUnit()
      Defines the unit used to calculate the capacity of the cache.

      When the unit is unknown, null is returned.

      Returns:
      the unit to be used to calculate the capacity of this cache.

    • getName

      String getName()
      Returns the name of the cache.
      Returns:
      the name of the cache.

    • setName

      void setName(String name)
      Sets the name of the cache
      Parameters:
      name - the name of the cache

    • getMaxCacheSize

      long getMaxCacheSize()
      Returns the maximum size of the cache.

      The value should be placed in context of the unit returned by getCapacityUnit(). When, for example, the capacity unit for this cache is Cache.CapacityUnit.BYTES, then a return value of 2048 should be interpreted as this cache having a capacity of 2048 bytes (or 2KB). When the capacity unit is Cache.CapacityUnit.ENTITIES then this cache can contain 2048 elements (irrespective of their byte size).

      If the cache grows larger than the maximum size, the least frequently used items will be removed.

      If the maximum cache size is set to -1, there is no size limit.

      Returns:
      the maximum size of the cache.

    • setMaxCacheSize

      void setMaxCacheSize(long maxSize)
      Sets the maximum size of the cache.

      The value should be placed in context of the unit returned by getCapacityUnit(). When, for example, the capacity unit for this cache is Cache.CapacityUnit.BYTES, then a return value of 2048 should be interpreted as this cache having a capacity of 2048 bytes (or 2KB). When the capacity unit is Cache.CapacityUnit.ENTITIES then this cache can contain 2048 elements (irrespective of their byte size).

      If the cache grows larger than the maximum size, the least frequently used items will be removed. If the maximum cache size is set to -1, there is no size limit.

      Note: If using the Hazelcast clustering plugin, this will only take effect if the cache is dynamically configured (not defined in the hazelcast-cache-config.xml file), and will not take effect until the next time the cache is created.

      Parameters:
      maxSize - the maximum size of the cache.

    • getMaxCacheSizeRemark

      default String getMaxCacheSizeRemark()
      An optional, human-readable remark on the maximum cache capacity configuration.
      Returns:
      an optional human-readable text

    • getMaxLifetime

      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.
      Returns:
      the maximum number of milliseconds before objects are expired.

    • setMaxLifetime

      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.

      Note: If using the Hazelcast clustering plugin, this will only take effect if the cache is dynamically configured (not defined in the hazelcast-cache-config.xml file), and will not take effect until the next time the cache is created.

      Parameters:
      maxLifetime - the maximum number of milliseconds before objects are expired.

    • getLongCacheSize

      long getLongCacheSize()
      Returns the size of the cache.

      The value should be placed in context of the unit returned by getCapacityUnit(). When, for example, the capacity unit for this cache is Cache.CapacityUnit.BYTES, then a return value of 2048 should be interpreted as all entities of this cache having a combined size of 2024 bytes (or 2KB). When the capacity unit is Cache.CapacityUnit.ENTITIES then this cache currently contains 2048 elements.

      The returned value can be an approximation.

      Returns:
      the size of the cache contents.

    • getCacheSizeRemark

      default String getCacheSizeRemark()
      An optional, human-readable remark on the current size of the cache.
      Returns:
      an optional human-readable text

    • getCacheHits

      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.

      Returns:
      the number of cache hits.

    • getCacheMisses

      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.

      Returns:
      the number of cache hits.

    • values

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

    • entrySet

      Set<Map.Entry<K,V>> entrySet()
      IMPORTANT: Unlike the standard Map.entrySet() implementation, the set returned from this method cannot be modified.
      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

      Set<K> keySet()
      IMPORTANT: Unlike the standard Map.keySet() implementation, the set returned from this method cannot be modified.
      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 Lock getLock(K key)
      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.

      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.

    • setSecretKey

      default void setSecretKey()

    • setSecretValue

      default void setSecretValue()

    • isKeySecret

      default boolean isKeySecret()

    • isValueSecret

      default boolean isValueSecret()

    • addClusteredCacheEntryListener

      String addClusteredCacheEntryListener(@Nonnull ClusteredCacheEntryListener<K,V> listener, boolean includeValues, boolean includeEventsFromLocalNode)
      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.
      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

      void removeClusteredCacheEntryListener(@Nonnull String listenerId)
      Removes a previously registered event listener.
      Parameters:
      listenerId - the identifier of the listener to be removed.