/**

  * Copyright 2005-2011 The Kuali Foundation

  *

  * Licensed under the Educational Community 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.opensource.org/licenses/ecl2.php

  *

  * 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.kuali.rice.kew.api.extension;

 import org.apache.commons.lang.StringUtils;

 import org.kuali.rice.core.api.reflect.ObjectDefinition;

 import org.kuali.rice.core.api.resourceloader.GlobalResourceLoader;

 import javax.xml.namespace.QName;

 /**

  * Contains utilities related to the loading of extension resources.

  *

  * @author Kuali Rice Team (rice.collab@kuali.org)

  */

 public final class ExtensionUtils {

     /**

      * Loads the extension object for the given extension definition.

      *

      * @param extensionDefinition the definition of the extension to load

      * @param <T> the type of the extension object which is to be loaded

      *

      * @return the loaded extension, or null if no extension was loaded for the given definition

      */

     public static <T> T loadExtension(ExtensionDefinitionContract extensionDefinition) {

         return ExtensionUtils.<T>loadExtension(extensionDefinition, null);

     }

     /**

      * Loads the extension object for the given extension definition, using the default applicationId if the given

      * extension definition has a null applicationId.

      *

      * @param extensionDefinition the definition of the extension to load

      * @param defaultApplicationId the application id to use when attempting to loading the extension if the

      * application id on the given definition is null

      * @param <T> the type of the extension object which is to be loaded

      *

      * @return the loaded extension, or null if no extension was loaded for the given definition

      */

     public static <T> T loadExtension(ExtensionDefinitionContract extensionDefinition, String defaultApplicationId) {

         T extensionService = null;

         // first check if the class name is a valid and available java class

         String resourceDescriptor = extensionDefinition.getResourceDescriptor();

         ObjectDefinition extensionObjectDefinition = getExtensionObjectDefinition(extensionDefinition,

                 defaultApplicationId);

         extensionService = GlobalResourceLoader.<T>getObject(extensionObjectDefinition);

         if (extensionService == null) {

             // if we can't find a class, try a service

             extensionService = GlobalResourceLoader.<T>getService(QName.valueOf(resourceDescriptor));

         }

         return extensionService;

     }

     private static ObjectDefinition getExtensionObjectDefinition(ExtensionDefinitionContract extensionDefinition, String defaultApplicationId) {

         if (StringUtils.isBlank(extensionDefinition.getApplicationId()) && StringUtils.isNotBlank(defaultApplicationId)) {

             return new ObjectDefinition(extensionDefinition.getResourceDescriptor(), defaultApplicationId);

         } else {

             return new ObjectDefinition(extensionDefinition.getResourceDescriptor(), extensionDefinition.getApplicationId());

         }

     }

     private ExtensionUtils() {

         throw new UnsupportedOperationException();

     }

 }