/*

  * $Id: ResourceBundleResources.java 358692 2005-12-23 03:37:26Z niallp $

  * $Revision: 358692 $

  * $Date: 2005-12-23 03:37:26 +0000 (Fri, 23 Dec 2005) $

  *

  * ====================================================================

  *

  *  Copyright 2003-2005 The Apache Software Foundation

  *

  *  Licensed 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.

  *

  */

 package org.apache.commons.resources.impl;

 import java.util.Collections;

 import java.util.Iterator;

 import java.util.Locale;

 import java.util.MissingResourceException;

 import java.util.ResourceBundle;

 import org.apache.commons.logging.Log;

 import org.apache.commons.logging.LogFactory;

 import org.apache.commons.resources.ResourcesException;

 import org.apache.commons.resources.ResourcesKeyException;

 import org.apache.commons.resources.util.IteratorEnumeration;

 /**

  * <p>Concrete implementation of 

  * {@link org.apache.commons.resources.Resources} that wraps a set

  * (one per Locale) of <code>java.util.ResourceBundle</code> instances

  * that share a common base name.</p>

  */

 public class ResourceBundleResources extends ResourcesBase {

     /**

      * <p>The logging instance for this class.</p>

      */

     private transient Log log =

         LogFactory.getLog(ResourceBundleResources.class);

     // ----------------------------------------------------------- Constructors

     /**

      * <p>Create a new {@link org.apache.commons.resources.Resources} 

      * instance with the specified

      * logical name and bundle base name.</p>

      *

      * @param name Logical name of the new instance

      * @param base Fully qualified base name of the <code>ResourceBundle</code>

      *  instances to be wrapped

      */

     public ResourceBundleResources(String name, String base) {

         super(name);

         this.base = base;

     }

     // ----------------------------------------------------- Instance Variables

     /**

      * <p>The fully qualified base name of the <code>ResourceBundle</code>

      * instances to be wrapped.</p>

      */

     private String base = null;

     // ------------------------------------------------------------- Properties

     /**

      * <p>Return the fully qualified base name of the

      * <code>ResourceBundle</code> instances we are wrapping.</p>

      * @return The base name of this resources instance.

      */

     public String getBase() {

         return (this.base);

     }

     /**

      * <p>Return an <code>Iterator</code> over the defined keys in this

      * {@link org.apache.commons.resources.Resources} instance.</p>

      *

      * @return The keys contained in this resources instance.

      */

     public Iterator getKeys() {

         try {

             ResourceBundle bundle = getBundle(null);

             return new IteratorEnumeration(bundle.getKeys());

         } catch (MissingResourceException e) {

             return Collections.EMPTY_LIST.iterator();

         }

     }

     // ---------------------------------------------- Content Retrieval Methods

     /**

      * <p>Return the content for the specified <code>key</code> as an

      * Object, localized based on the specified <code>locale</code>.

      * </p>

      *

      * @param key Identifier for the requested content

      * @param locale Locale with which to localize retrieval,

      *  or <code>null</code> for the default Locale

      * @return content for a specified key.

      *

      * @exception ResourcesException if an error occurs retrieving or

      *  returning the requested content

      * @exception ResourcesKeyException if the no value for the specified

      *  key was found, and <code>isReturnNull()</code> returns

      *  <code>false</code>

      */

     public Object getObject(String key, Locale locale) {

         if (getLog().isTraceEnabled()) {

             getLog().trace("Retrieving message for key '" + key + "' and locale '"

                       + locale + "'");

         }

         try {

             ResourceBundle bundle = getBundle(locale);

             Object object = bundle.getObject(key);

             if (getLog().isTraceEnabled()) {

                 getLog().trace("Retrieved object for key '" + key + 

                                "' and locale '" + locale +

                                "' is '" + object + "'");

             }

             return object;

         } catch (MissingResourceException e) {

             if (getLog().isTraceEnabled()) {

                 getLog().trace("No resource found for key '" + key + 

                                "' and locale '" + locale + "'");

             }

             if (isReturnNull()) {

                 return (null);

             } else {

                 throw new ResourcesKeyException(key);

             }

         }

     }

     // ------------------------------------------------------ Protected Methods

     /**

      * <p>Return the appropriate <code>ResourceBundle</code> instance

      * that corresponds to the specified <code>locale</code> parameter.

      * The first time a particular bundle is requested, cache it so

      * that subsequent requests will operate more quickly.</p>

      *

      * @param locale Locale with which to localize retrieval,

      *  or <code>null</code> for the default Locale

      * @return The Resource Bundle corresponding to the locale and time zone.

      *

      * @exception MissingResourceException if the requested Resourcebundle

      *  cannot be acquired

      */

     protected ResourceBundle getBundle(Locale locale)

         throws MissingResourceException {

         if (locale == null) {

             locale = Locale.getDefault();

         }

         // Locate the appropriate ClassLoader

         ClassLoader loader = getClassLoader();

         // Locate the requested ResourceBundle instance

         ResourceBundle bundle = ResourceBundle.getBundle(base, locale, loader);

         return (bundle);

     }

     /**

      * <p>Return the <code>ClassLoader</code> for which we are mapping

      * <code>ResourceBundle</code> instances.</p>

      * @return The Class Loader for the resource bundle.

      */

     protected ClassLoader getClassLoader() {

         ClassLoader loader = Thread.currentThread().getContextClassLoader();

         if (loader == null) {

             loader = this.getClass().getClassLoader();

         }

         return (loader);

     }

     /**

      * Accessor method for Log instance.

      *

      * The Log instance variable is transient and

      * accessing it through this method ensures it

      * is re-initialized when this instance is

      * de-serialized.

      *

      * @return The Log instance.

      */

     private Log getLog() {

         if (log == null) {

             log =  LogFactory.getLog(ResourceBundleResources.class);

         }

         return log;

     }

 }