001    /**
002     * Copyright 2005-2013 The Kuali Foundation
003     *
004     * Licensed under the Educational Community License, Version 2.0 (the "License");
005     * you may not use this file except in compliance with the License.
006     * You may obtain a copy of the License at
007     *
008     * http://www.opensource.org/licenses/ecl2.php
009     *
010     * Unless required by applicable law or agreed to in writing, software
011     * distributed under the License is distributed on an "AS IS" BASIS,
012     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013     * See the License for the specific language governing permissions and
014     * limitations under the License.
015     */
016    package org.kuali.rice.kew.api.extension;
017    
018    import org.apache.commons.lang.StringUtils;
019    import org.kuali.rice.core.api.reflect.ObjectDefinition;
020    import org.kuali.rice.core.api.resourceloader.GlobalResourceLoader;
021    
022    import javax.xml.namespace.QName;
023    
024    /**
025     * Contains utilities related to the loading of extension resources.
026     *
027     * @author Kuali Rice Team (rice.collab@kuali.org)
028     */
029    public final class ExtensionUtils {
030    
031        /**
032         * Loads the extension object for the given extension definition.
033         *
034         * @param extensionDefinition the definition of the extension to load
035         * @param <T> the type of the extension object which is to be loaded
036         *
037         * @return the loaded extension, or null if no extension was loaded for the given definition
038         */
039        public static <T> T loadExtension(ExtensionDefinitionContract extensionDefinition) {
040            return ExtensionUtils.<T>loadExtension(extensionDefinition, null);
041        }
042    
043        /**
044         * Loads the extension object for the given extension definition, using the default applicationId if the given
045         * extension definition has a null applicationId.
046         *
047         * @param extensionDefinition the definition of the extension to load
048         * @param defaultApplicationId the application id to use when attempting to loading the extension if the
049         * application id on the given definition is null
050         * @param <T> the type of the extension object which is to be loaded
051         *
052         * @return the loaded extension, or null if no extension was loaded for the given definition
053         */
054        public static <T> T loadExtension(ExtensionDefinitionContract extensionDefinition, String defaultApplicationId) {
055            T extensionService = null;
056            // first check if the class name is a valid and available java class
057            String resourceDescriptor = extensionDefinition.getResourceDescriptor();
058            ObjectDefinition extensionObjectDefinition = getExtensionObjectDefinition(extensionDefinition,
059                    defaultApplicationId);
060            extensionService = GlobalResourceLoader.<T>getObject(extensionObjectDefinition);
061            if (extensionService == null) {
062                // if we can't find a class, try a service
063                extensionService = GlobalResourceLoader.<T>getService(QName.valueOf(resourceDescriptor));
064            }
065            return extensionService;
066        }
067    
068        private static ObjectDefinition getExtensionObjectDefinition(ExtensionDefinitionContract extensionDefinition, String defaultApplicationId) {
069            if (StringUtils.isBlank(extensionDefinition.getApplicationId()) && StringUtils.isNotBlank(defaultApplicationId)) {
070                return new ObjectDefinition(extensionDefinition.getResourceDescriptor(), defaultApplicationId);
071            } else {
072                return new ObjectDefinition(extensionDefinition.getResourceDescriptor(), extensionDefinition.getApplicationId());
073            }
074        }
075    
076        private ExtensionUtils() {
077            throw new UnsupportedOperationException();
078        }
079    
080    }