/*

  * Copyright (C) 1998-2000 Semiotek Inc.  All Rights Reserved.

  *

  * Redistribution and use in source and binary forms, with or without

  * modification, are permitted under the terms of either of the following

  * Open Source licenses:

  *

  * The GNU General Public License, version 2, or any later version, as

  * published by the Free Software Foundation

  * (http://www.fsf.org/copyleft/gpl.html);

  *

  *  or

  *

  * The Semiotek Public License (http://webmacro.org/LICENSE.)

  *

  * This software is provided "as is", with NO WARRANTY, not even the

  * implied warranties of fitness to purpose, or merchantability. You

  * assume all risks and liabilities associated with its use.

  *

  * See www.webmacro.org for more information on the WebMacro project.

  */

 package org.webmacro.resource;

 import org.slf4j.Logger;

 import org.slf4j.LoggerFactory;

 import org.webmacro.Broker;

 import org.webmacro.InitException;

 import org.webmacro.Provider;

 import org.webmacro.ResourceException;

 import org.webmacro.util.Settings;

 /**

  * CacheManager is an abstract base class for providers which wish to

  * implement caching functionality.  By extending CachingProvider and

  * implementing the methods in ResourceLoader, a provider can

  * automatically support caching using any CacheManager.  CachingProvider

  * looks in the properties file to find the desired cache manager.

  * @since 0.96

  */

 abstract public class CachingProvider implements Provider,

         ResourceLoader

 {

     static Logger _log =  LoggerFactory.getLogger(CachingProvider.class);

     private CacheManager _cache;

     protected boolean _cacheSupportsReload;

     public CachingProvider ()

     {

     }

     /**

      * If you override this method be sure and call super.init(...)

      */

     public void init (Broker b, Settings config) throws InitException

     {

         String cacheManager;

         cacheManager = b.getSetting("CachingProvider." + getType()

                 + ".CacheManager");

         if (cacheManager == null)

             cacheManager = b.getSetting("CachingProvider.*.CacheManager");

         if (cacheManager == null || cacheManager.equals(""))

         {

             _log.info("CachingProvider: No cache manager specified for "

                     + getType() + ", using TrivialCacheManager");

             _cache = new TrivialCacheManager();

         }

         else

         {

             try

             {

                 _cache = (CacheManager) b.classForName(cacheManager).newInstance();

             }

             catch (Exception e)

             {

                 _log.warn("Unable to load cache manager " + cacheManager

                         + " for resource type " + getType()

                         + ", using TrivialCacheManager.  Reason:\n" + e);

                 _cache = new TrivialCacheManager();

             }

         }

         _cache.init(b, config, getType());

         _cacheSupportsReload = _cache.supportsReload();

     }

     /**

      * Clear the cache. If you override this method be sure

      * and call super.flush().

      */

     public void flush ()

     {

         _cache.flush();

     }

     /**

      * Close down the provider. If you override this method be

      * sure and call super.destroy().

      */

     public void destroy ()

     {

         _cache.destroy();

     }

     /**

      * Get the object associated with the specific query, using the

      * specified cache manager.

      */

     public Object get (String query) throws ResourceException

     {

         return _cache.get(query, this);

     }

     /**

      * Delegates to ResourceLoader implementers the load operation

      * by casting the query as a string and invoking the

      * implemented method.

      */

     public Object load (Object query, CacheElement ce)

             throws ResourceException

     {

         return ((ResourceLoader) this).load((String) query, ce);

     }

     public String toString ()

     {

         return "CachingProvider(type = " + getType() + ")";

     }

 }