Package net.sourceforge.jtds.jdbc.cache

Class ProcedureCache

  • All Implemented Interfaces:
    StatementCache
    public class ProcedureCache
extends java.lang.Object
implements StatementCache
    LRU cache for procedures and statement handles.
    Version:
    $Id: ProcedureCache.java,v 1.5 2005-07-05 16:44:25 alin_sinpalean Exp $

    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description
      private static class  ProcedureCache.CacheEntry
      Encapsulates the cached Object and implements the linked list used to implement the LRU logic.

    • Field Summary

      Fields 
      Modifier and Type Field Description
      private java.util.HashMap cache
      The actual cache instance.
      (package private) int cacheSize
      Maximum cache size or 0 to disable.
      (package private) java.util.ArrayList free
      List of redundant cache entries.
      (package private) ProcedureCache.CacheEntry head
      Head node of the linked list.
      private static int MAX_INITIAL_SIZE
      The maximum initial HashMap size.
      (package private) ProcedureCache.CacheEntry tail
      Tail node of the linked list.

    • Constructor Summary

      Constructors 
      Constructor Description
      ProcedureCache​(int cacheSize)
      Constructs a new statement cache.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      java.lang.Object get​(java.lang.String key)
      Retrieves a ProcEntry object from the cache.
      java.util.Collection getObsoleteHandles​(java.util.Collection handles)
      Obtains a list of statement handles or procedures that can now be dropped.
      void put​(java.lang.String key, java.lang.Object handle)
      Inserts a new entry, identified by a key, into the cache.
      void remove​(java.lang.String key)
      Removes a redundant entry from the cache.
      private void scavengeCache()
      Removes unused entries trying to bring down the cache to the requested size.

      • Methods inherited from class java.lang.Object

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

    • Field Detail

      • MAX_INITIAL_SIZE

        private static final int MAX_INITIAL_SIZE
        The maximum initial HashMap size.
        See Also:
        Constant Field Values

      • cache

        private java.util.HashMap cache
        The actual cache instance.

      • cacheSize

        int cacheSize
        Maximum cache size or 0 to disable.

      • free

        java.util.ArrayList free
        List of redundant cache entries.

    • Constructor Detail

      • ProcedureCache

        public ProcedureCache​(int cacheSize)
        Constructs a new statement cache.
        Parameters:
        cacheSize - maximum cache size or 0 to disable caching

    • Method Detail

      • get

        public java.lang.Object get​(java.lang.String key)
        Retrieves a ProcEntry object from the cache.

        If the entry exists it is moved to the front of the linked list to keep it alive as long as possible.

        Specified by:
        get in interface StatementCache
        Parameters:
        key - the key value identifying the required entry
        Returns:
        the keyed entry as an Object or null if the entry does not exist

      • put

        public void put​(java.lang.String key,
                java.lang.Object handle)
        Inserts a new entry, identified by a key, into the cache.

        If the cache is full then one or more entries are removed and transferred to a list for later destruction.

        Specified by:
        put in interface StatementCache
        Parameters:
        key - value used to identify the entry
        handle - proc entry to be inserted into the cache

      • remove

        public void remove​(java.lang.String key)
        Removes a redundant entry from the cache.
        Specified by:
        remove in interface StatementCache
        Parameters:
        key - value that identifies the cache entry

      • getObsoleteHandles

        public java.util.Collection getObsoleteHandles​(java.util.Collection handles)
        Obtains a list of statement handles or procedures that can now be dropped.
        Specified by:
        getObsoleteHandles in interface StatementCache
        Parameters:
        handles - a collection of single use statements that will be returned for dropping if the cache is disabled
        Returns:
        the collection of redundant statments for dropping

      • scavengeCache

        private void scavengeCache()
        Removes unused entries trying to bring down the cache to the requested size. The removed entries are placed in the free list.

        Note: entries that are in use will not be removed so it is possible for the cache to still be larger than cacheSize after the call finishes.