package org.apache.commons.jcs3.access;
   
   /*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you under the Apache License, Version 2.0 (the
    * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   */
  
  import java.io.IOException;
  
  import org.apache.commons.jcs3.access.behavior.ICacheAccessManagement;
  import org.apache.commons.jcs3.access.exception.CacheException;
  import org.apache.commons.jcs3.engine.behavior.ICompositeCacheAttributes;
  import org.apache.commons.jcs3.engine.behavior.IElementAttributes;
  import org.apache.commons.jcs3.engine.control.CompositeCache;
  import org.apache.commons.jcs3.engine.stats.behavior.ICacheStats;
  
  /**
   * This class provides the common methods for all types of access to the cache.
   * <p>
   * An instance of this class is tied to a specific cache region. Static methods are provided to get
   * such instances.
   * <p>
   * Using this class you can retrieve an item, the item's wrapper, and the element's configuration.  You can also put an
   * item in the cache, remove an item, and clear a region.
   * <p>
   * The JCS class is the preferred way to access these methods.
   */
  public abstract class AbstractCacheAccess<K, V>
      implements ICacheAccessManagement
  {
      /**
       * The cache that a given instance of this class provides access to.
       * <p>
       * TODO Should this be the interface?
       */
      private final CompositeCache<K, V> cacheControl;
  
      /**
       * Constructor for the CacheAccess object.
       * <p>
       * @param cacheControl The cache which the created instance accesses
       */
      protected AbstractCacheAccess( final CompositeCache<K, V> cacheControl )
      {
          this.cacheControl = cacheControl;
      }
  
      /**
       * Removes all of the elements from a region.
       * <p>
       * @throws CacheException
       */
      @Override
      public void clear()
          throws CacheException
      {
          try
          {
              this.getCacheControl().removeAll();
          }
          catch ( final IOException e )
          {
              throw new CacheException( e );
          }
      }
  
      /**
       * This method is does not reset the attributes for items already in the cache. It could
       * potentially do this for items in memory, and maybe on disk (which would be slow) but not
       * remote items. Rather than have unpredictable behavior, this method just sets the default
       * attributes. Items subsequently put into the cache will use these defaults if they do not
       * specify specific attributes.
       * <p>
       * @param attr the default attributes.
       * @throws CacheException if something goes wrong.
       */
      @Override
      public void setDefaultElementAttributes( final IElementAttributes attr )
          throws CacheException
      {
          this.getCacheControl().setElementAttributes( attr );
      }
  
      /**
       * Retrieves A COPY OF the default element attributes used by this region. This does not provide
      * a reference to the element attributes.
      * <p>
      * Each time an element is added to the cache without element attributes, the default element
      * attributes are cloned.
      * <p>
      * @return the default element attributes used by this region.
      * @throws CacheException
      */
     @Override
     public IElementAttributes getDefaultElementAttributes()
         throws CacheException
     {
         return this.getCacheControl().getElementAttributes();
     }
 
     /**
      * This returns the ICacheStats object with information on this region and its auxiliaries.
      * <p>
      * This data can be formatted as needed.
      * <p>
      * @return ICacheStats
      */
     @Override
     public ICacheStats getStatistics()
     {
         return this.getCacheControl().getStatistics();
     }
 
     /**
      * @return A String version of the stats.
      */
     @Override
     public String getStats()
     {
         return this.getCacheControl().getStats();
     }
 
     /**
      * Dispose this region. Flushes objects to and closes auxiliary caches. This is a shutdown
      * command!
      * <p>
      * To simply remove all elements from the region use clear().
      */
     @Override
     public void dispose()
     {
         this.getCacheControl().dispose();
     }
 
     /**
      * Gets the ICompositeCacheAttributes of the cache region.
      * <p>
      * @return ICompositeCacheAttributes, the controllers config info, defined in the top section of
      *         a region definition.
      */
     @Override
     public ICompositeCacheAttributes getCacheAttributes()
     {
         return this.getCacheControl().getCacheAttributes();
     }
 
     /**
      * Sets the ICompositeCacheAttributes of the cache region.
      * <p>
      * @param cattr The new ICompositeCacheAttribute value
      */
     @Override
     public void setCacheAttributes( final ICompositeCacheAttributes cattr )
     {
         this.getCacheControl().setCacheAttributes( cattr );
     }
 
     /**
      * This instructs the memory cache to remove the <i>numberToFree</i> according to its eviction
      * policy. For example, the LRUMemoryCache will remove the <i>numberToFree</i> least recently
      * used items. These will be spooled to disk if a disk auxiliary is available.
      * <p>
      * @param numberToFree
      * @return the number that were removed. if you ask to free 5, but there are only 3, you will
      *         get 3.
      * @throws CacheException
      */
     @Override
     public int freeMemoryElements( final int numberToFree )
         throws CacheException
     {
         int numFreed = -1;
         try
         {
             numFreed = this.getCacheControl().getMemoryCache().freeElements( numberToFree );
         }
         catch ( final IOException ioe )
         {
             final String message = "Failure freeing memory elements.";
             throw new CacheException( message, ioe );
         }
         return numFreed;
     }
 
     public CompositeCache<K, V> getCacheControl() {
         return cacheControl;
     }
 
 }