001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.commons.discovery;
018    
019    import java.net.URL;
020    import java.security.AccessController;
021    import java.security.PrivilegedAction;
022    
023    import org.apache.commons.discovery.log.DiscoveryLogFactory;
024    import org.apache.commons.logging.Log;
025    
026    
027    /**
028     * 'Resource' located by discovery.
029     * Naming of methods becomes a real pain ('getClass()')
030     * so I've patterned this after ClassLoader...
031     * 
032     * I think it works well as it will give users a point-of-reference.
033     * 
034     * @author Richard A. Sitze
035     */
036    public class ResourceClass extends Resource
037    {
038        private static Log log = DiscoveryLogFactory.newLog(ResourceClass.class);
039        public static void setLog(Log _log) {
040            log = _log;
041        }
042        protected Class       resourceClass;
043    
044        public ResourceClass(Class resourceClass, URL resource) {
045            super(resourceClass.getName(), resource, resourceClass.getClassLoader());
046            this.resourceClass = resourceClass;
047        }
048    
049        public ResourceClass(String resourceName, URL resource, ClassLoader loader) {
050            super(resourceName, resource, loader);
051        }
052        
053        /**
054         * Get the value of resourceClass.
055         * Loading the class does NOT guarentee that the class can be
056         * instantiated.  Go figure.
057         * The class can be instantiated when the class is linked/resolved,
058         * and all dependencies are resolved.
059         * Various JDKs do this at different times, so beware:
060         * java.lang.NoClassDefFoundError when
061         * calling Class.getDeclaredMethod() (JDK14),
062         * java.lang.reflect.InvocationTargetException
063         * (wrapping java.lang.NoClassDefFoundError) when calling
064         * java.lang.newInstance (JDK13),
065         * and who knows what else..
066         *
067         * @return value of resourceClass.
068         */
069        public Class loadClass() {
070            if (resourceClass == null  &&  getClassLoader() != null) {
071                if (log.isDebugEnabled())
072                    log.debug("loadClass: Loading class '" + getName() + "' with " + getClassLoader());
073    
074                resourceClass = (Class)AccessController.doPrivileged(
075                    new PrivilegedAction() {
076                        public Object run() {
077                            try {
078                                return getClassLoader().loadClass(getName());
079                            } catch (ClassNotFoundException e) {
080                                return null;
081                            }
082                        }
083                    });
084            }
085            return resourceClass;
086        }
087        
088        public String toString() {
089            return "ResourceClass[" + getName() +  ", " + getResource() + ", " + getClassLoader() + "]";
090        }
091    }