package org.apache.torque.manager;
   
   /*
    * 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.Serializable;
  import java.util.HashMap;
  import java.util.Map;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.jcs.access.GroupCacheAccess;
  import org.apache.jcs.access.exception.CacheException;
  import org.apache.torque.TorqueException;
  
  /**
   * This class provides a cache for convenient storage of method
   * results.
   *
   * @author <a href="mailto:jmcnally@collab.net">John McNally</a>
   * @version $Id: MethodResultCache.java 1379317 2012-08-31 06:56:48Z tfischer $
   */
  public class MethodResultCache
  {
      /** The underlying jcs cache. */
      private GroupCacheAccess jcsCache;
  
      /** All chache groups which are currently filled. */
      private Map<String, Object> groups;
  
      /** Logging */
      private static Log log = LogFactory.getLog(MethodResultCache.class);
  
      /**
       * Constructor
       *
       * @param cache the cache instance to use
       */
      public MethodResultCache(GroupCacheAccess cache)
      {
          this.jcsCache = cache;
          groups = new HashMap<String, Object>();
      }
  
      /**
       * Allows subclasses to have ctors that do not require a cache.
       * This is used by NullMethodResultCache which has no-op versions
       * of all methods.
       */
      protected MethodResultCache()
      {
          //empty
      }
  
      /**
       * Clear the cache
       */
      public void clear()
      {
          if (jcsCache != null)
          {
              try
              {
                  jcsCache.clear();
                  groups.clear();
              }
              catch (CacheException ce)
              {
                  log.error(new TorqueException(
                      "Could not clear cache due to internal JCS error.", ce));
              }
          }
      }
  
      protected Object getImpl(MethodCacheKey key)
      {
          Object result = null;
          if (jcsCache != null)
          {
              synchronized (this)
              {
                  result = jcsCache.getFromGroup(key, key.getGroupKey());
              }
         }
 
         if (result != null && log.isDebugEnabled())
         {
             log.debug("MethodResultCache saved expensive operation: " + key);
         }
 
         return result;
     }
 
 
     protected Object putImpl(MethodCacheKey key, Object value)
         throws TorqueException
     {
         //register the group, if this is the first occurrence
         String group = key.getGroupKey();
         if (!groups.containsKey(group))
         {
             groups.put(group, null);
         }
 
         Object old = null;
         if (jcsCache != null)
         {
             try
             {
                 synchronized (this)
                 {
                     old = jcsCache.getFromGroup(key, group);
                     jcsCache.putInGroup(key, group, value);
                 }
             }
             catch (CacheException ce)
             {
                 throw new TorqueException
                     ("Could not cache due to internal JCS error", ce);
             }
         }
         return old;
     }
 
     protected Object removeImpl(MethodCacheKey key)
     {
         Object old = null;
         if (jcsCache != null)
         {
             synchronized (this)
             {
                 old = jcsCache.getFromGroup(key, key.getGroupKey());
                 jcsCache.remove(key, key.getGroupKey());
             }
         }
         return old;
     }
 
     /**
      * Get an object from the method cache
      *
      * @param instanceOrClass the Object on which the method is invoked.  if
      * the method is static, a String representing the class name is used.
      * @param method the method name
      * @param arg optional arguments for the method
      *
      * @return the object or null if it does not exist
      */
     @SuppressWarnings("unchecked")
     public <T> T get(Serializable instanceOrClass, String method, Serializable ... arg)
     {
         T result = null;
         if (jcsCache != null)
         {
             try
             {
                 MethodCacheKey key = new MethodCacheKey(instanceOrClass, method, arg);
                 result = (T) getImpl(key);
             }
             catch (Exception e)
             {
                 log.error("Problem getting object from cache", e);
             }
         }
 
         return result;
     }
 
     /**
      * Put an object into the method cache
      *
      * @param value the object to put into the cache
      * @param instanceOrClass the Object on which the method is invoked.  if
      * the method is static, a String representing the class name is used.
      * @param method the method name
      * @param arg optional arguments for the method
      */
     public <T> void put(T value, Serializable instanceOrClass, String method, Serializable ... arg)
     {
         try
         {
             MethodCacheKey key = new MethodCacheKey(instanceOrClass, method, arg);
             putImpl(key, value);
         }
         catch (Exception e)
         {
             log.error("Problem putting object into cache", e);
         }
     }
 
     /**
      * Remove all objects of the same group
      *
      * @param instanceOrClass the Object on which the method is invoked.  if
      * the method is static, a String representing the class name is used.
      * @param method the method name
      */
     public void removeAll(Serializable instanceOrClass, String method)
     {
         if (jcsCache != null)
         {
             try
             {
                 MethodCacheKey key = new MethodCacheKey(instanceOrClass, method);
                 String groupName = key.getGroupKey();
                 jcsCache.invalidateGroup(groupName);
                 groups.remove(groupName);
             }
             catch (Exception e)
             {
                 log.error("Problem removing all", e);
             }
         }
     }
 
     /**
      * Remove object from method cache
      *
      * @param instanceOrClass the Object on which the method is invoked.  if
      * the method is static, a String representing the class name is used.
      * @param method the method name
      * @param arg optional arguments for the method
      *
      * @return the removed object
      */
     @SuppressWarnings("unchecked")
     public <T> T remove(Serializable instanceOrClass, String method, Serializable ... arg)
     {
         T result = null;
         if (jcsCache != null)
         {
             try
             {
                 MethodCacheKey key = new MethodCacheKey(instanceOrClass, method, arg);
                 result = (T) removeImpl(key);
             }
             catch (Exception e)
             {
                 log.error("Problem removing object from cache", e);
             }
         }
 
         return result;
     }
 }