Package org.jboss.util

Class LRUCachePolicy

  • All Implemented Interfaces:
    CachePolicy
    public class LRUCachePolicy
extends java.lang.Object
implements CachePolicy
    Implementation of a Least Recently Used cache policy.
    Version:
    $Revision$

    • Field Summary

      Fields 
      Modifier and Type Field Description
      protected LRUCachePolicy.LRUList m_list
      The linked list used to implement the LRU algorithm
      protected java.util.Map m_map
      The map holding the cached objects
      protected int m_maxCapacity
      The maximum capacity of this cache
      protected int m_minCapacity
      The minimum capacity of this cache

    • Constructor Summary

      Constructors 
      Constructor Description
      LRUCachePolicy()
      Creates a LRU cache policy object with zero cache capacity.
      LRUCachePolicy​(int min, int max)
      Creates a LRU cache policy object with the specified minimum and maximum capacity.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      protected void ageOut​(LRUCachePolicy.LRUCacheEntry entry)
      Callback method called when the cache algorithm ages out of the cache the given entry.
      protected void cacheMiss()
      Callback method called when a cache miss happens.
      void create()
      Initializes the cache, creating all required objects and initializing their values.
      protected LRUCachePolicy.LRUCacheEntry createCacheEntry​(java.lang.Object key, java.lang.Object value)
      Factory method for cache entries
      protected LRUCachePolicy.LRUList createList()
      Factory method for the linked list used by this cache implementation.
      protected java.util.Map createMap()
      Create map holding entries.
      void destroy()
      Destroys the cache that is now unusable.
      void flush()
      Flushes the cached objects from the cache.
      java.lang.Object get​(java.lang.Object key)
      Returns the object paired with the specified key if it's present in the cache, otherwise must return null.
      void insert​(java.lang.Object key, java.lang.Object o)
      Inserts the specified object into the cache following the implemented policy.
      java.lang.Object peek​(java.lang.Object key)
      Returns the object paired with the specified key if it's present in the cache, otherwise must return null.
      void remove​(java.lang.Object key)
      Remove the cached object paired with the specified key.
      int size()  
      void start()
      Starts this cache that is now ready to be used.
      void stop()
      Stops this cache thus flush()ing all cached objects.

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Field Detail

      • m_map

        protected java.util.Map m_map
        The map holding the cached objects

      • m_maxCapacity

        protected int m_maxCapacity
        The maximum capacity of this cache

      • m_minCapacity

        protected int m_minCapacity
        The minimum capacity of this cache

    • Constructor Detail

      • LRUCachePolicy

        public LRUCachePolicy()
        Creates a LRU cache policy object with zero cache capacity.
        See Also:
        create()

      • LRUCachePolicy

        public LRUCachePolicy​(int min,
                      int max)
        Creates a LRU cache policy object with the specified minimum and maximum capacity.
        Parameters:
        min -
        max -
        See Also:
        create()

    • Method Detail

      • createMap

        protected java.util.Map createMap()
        Create map holding entries.
        Returns:
        the map

      • create

        public void create()
        Initializes the cache, creating all required objects and initializing their values.
        Specified by:
        create in interface CachePolicy
        See Also:
        start(), destroy()

      • start

        public void start()
        Starts this cache that is now ready to be used.
        Specified by:
        start in interface CachePolicy
        See Also:
        create(), stop()

      • stop

        public void stop()
        Stops this cache thus flush()ing all cached objects.
        After this method is called, a call to start() will restart the cache.
        Specified by:
        stop in interface CachePolicy
        See Also:
        start(), destroy()

      • destroy

        public void destroy()
        Destroys the cache that is now unusable.
        To have it working again it must be re-create()ed and re-start()ed.
        Specified by:
        destroy in interface CachePolicy
        See Also:
        create()

      • get

        public java.lang.Object get​(java.lang.Object key)
        Description copied from interface: CachePolicy
        Returns the object paired with the specified key if it's present in the cache, otherwise must return null.
        Implementations of this method must have complexity of order O(1). Differently from CachePolicy.peek(java.lang.Object) this method not only return whether the object is present in the cache or not, but also applies the implemented policy that will "refresh" the cached object in the cache, because this cached object was really requested.
        Specified by:
        get in interface CachePolicy
        Parameters:
        key - the key paired with the object
        Returns:
        the object
        See Also:
        CachePolicy.peek(java.lang.Object)

      • peek

        public java.lang.Object peek​(java.lang.Object key)
        Description copied from interface: CachePolicy
        Returns the object paired with the specified key if it's present in the cache, otherwise must return null.
        Implementations of this method must have complexity of order O(1). This method should not apply the implemented caching policy to the object paired with the given key, so that a client can query if an object is cached without "refresh" its cache status. Real requests for the object must be done using CachePolicy.get(java.lang.Object).
        Specified by:
        peek in interface CachePolicy
        Parameters:
        key - the key paired with the object
        Returns:
        the object
        See Also:
        CachePolicy.get(java.lang.Object)

      • insert

        public void insert​(java.lang.Object key,
                   java.lang.Object o)
        Description copied from interface: CachePolicy
        Inserts the specified object into the cache following the implemented policy.
        Implementations of this method must have complexity of order O(1).
        Specified by:
        insert in interface CachePolicy
        Parameters:
        key - the key paired with the object
        o - the object to cache
        See Also:
        CachePolicy.remove(java.lang.Object)

      • flush

        public void flush()
        Description copied from interface: CachePolicy
        Flushes the cached objects from the cache.
        Specified by:
        flush in interface CachePolicy

      • size

        public int size()
        Specified by:
        size in interface CachePolicy
        Returns:
        the size of the cache

      • createList

        protected LRUCachePolicy.LRUList createList()
        Factory method for the linked list used by this cache implementation.
        Returns:
        the lru list

      • ageOut

        protected void ageOut​(LRUCachePolicy.LRUCacheEntry entry)
        Callback method called when the cache algorithm ages out of the cache the given entry.
        The implementation here is removing the given entry from the cache.
        Parameters:
        entry -

      • cacheMiss

        protected void cacheMiss()
        Callback method called when a cache miss happens.

      • createCacheEntry

        protected LRUCachePolicy.LRUCacheEntry createCacheEntry​(java.lang.Object key,
                                                        java.lang.Object value)
        Factory method for cache entries
        Parameters:
        key -
        value -
        Returns:
        the entry