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/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you 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.cxf.common.classloader;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.List;

/**
 * This class is extremely useful for loading resources and classes in a fault
 * tolerant manner that works across different applications servers. Do not
 * touch this unless you're a grizzled classloading guru veteran who is going to
 * verify any change on 6 different application servers.
 */
public final class ClassLoaderUtils {
    
    private ClassLoaderUtils() {
    }
    
    public static class ClassLoaderHolder {
        ClassLoader loader;
        ClassLoaderHolder(ClassLoader c) {
            loader = c;
        }
        
        public void reset() {
            ClassLoaderUtils.setThreadContextClassloader(loader);
        }
    }
    public static ClassLoaderHolder setThreadContextClassloader(final ClassLoader newLoader) {
        return AccessController.doPrivileged(new PrivilegedAction() {
            public ClassLoaderHolder run() {
                ClassLoader l = Thread.currentThread().getContextClassLoader();
                Thread.currentThread().setContextClassLoader(newLoader);
                return new ClassLoaderHolder(l);
            }
        });
    }
    
    
    /**
     * Load a given resource. 

This method will try to load the resource * using the following methods (in order): *

    *
  • From Thread.currentThread().getContextClassLoader() *
  • From ClassLoaderUtil.class.getClassLoader() *
  • callingClass.getClassLoader() *
* * @param resourceName The name of the resource to load * @param callingClass The Class object of the calling object */ public static URL getResource(String resourceName, Class callingClass) { URL url = Thread.currentThread().getContextClassLoader().getResource(resourceName); if (url == null && resourceName.startsWith("/")) { //certain classloaders need it without the leading / url = Thread.currentThread().getContextClassLoader() .getResource(resourceName.substring(1)); } ClassLoader cluClassloader = ClassLoaderUtils.class.getClassLoader(); if (cluClassloader == null) { cluClassloader = ClassLoader.getSystemClassLoader(); } if (url == null) { url = cluClassloader.getResource(resourceName); } if (url == null && resourceName.startsWith("/")) { //certain classloaders need it without the leading / url = cluClassloader.getResource(resourceName.substring(1)); } if (url == null) { ClassLoader cl = callingClass.getClassLoader(); if (cl != null) { url = cl.getResource(resourceName); } } if (url == null) { url = callingClass.getResource(resourceName); } if ((url == null) && (resourceName != null) && (resourceName.charAt(0) != '/')) { return getResource('/' + resourceName, callingClass); } return url; } /** * Load a given resources.

This method will try to load the resources * using the following methods (in order): *

    *
  • From Thread.currentThread().getContextClassLoader() *
  • From ClassLoaderUtil.class.getClassLoader() *
  • callingClass.getClassLoader() *
* * @param resourceName The name of the resource to load * @param callingClass The Class object of the calling object */ public static List getResources(String resourceName, Class callingClass) { List ret = new ArrayList(); Enumeration urls = new Enumeration() { public boolean hasMoreElements() { return false; } public URL nextElement() { return null; } }; try { urls = Thread.currentThread().getContextClassLoader() .getResources(resourceName); } catch (IOException e) { //ignore } if (!urls.hasMoreElements() && resourceName.startsWith("/")) { //certain classloaders need it without the leading / try { urls = Thread.currentThread().getContextClassLoader() .getResources(resourceName.substring(1)); } catch (IOException e) { // ignore } } ClassLoader cluClassloader = ClassLoaderUtils.class.getClassLoader(); if (cluClassloader == null) { cluClassloader = ClassLoader.getSystemClassLoader(); } if (!urls.hasMoreElements()) { try { urls = cluClassloader.getResources(resourceName); } catch (IOException e) { // ignore } } if (!urls.hasMoreElements() && resourceName.startsWith("/")) { //certain classloaders need it without the leading / try { urls = cluClassloader.getResources(resourceName.substring(1)); } catch (IOException e) { // ignore } } if (!urls.hasMoreElements()) { ClassLoader cl = callingClass.getClassLoader(); if (cl != null) { try { urls = cl.getResources(resourceName); } catch (IOException e) { // ignore } } } if (!urls.hasMoreElements()) { URL url = callingClass.getResource(resourceName); if (url != null) { ret.add(url); } } while (urls.hasMoreElements()) { ret.add(urls.nextElement()); } if (ret.isEmpty() && (resourceName != null) && (resourceName.charAt(0) != '/')) { return getResources('/' + resourceName, callingClass); } return ret; } /** * This is a convenience method to load a resource as a stream.

The * algorithm used to find the resource is given in getResource() * * @param resourceName The name of the resource to load * @param callingClass The Class object of the calling object */ public static InputStream getResourceAsStream(String resourceName, Class callingClass) { URL url = getResource(resourceName, callingClass); try { return (url != null) ? url.openStream() : null; } catch (IOException e) { return null; } } /** * Load a class with a given name.

It will try to load the class in the * following order: *

    *
  • From Thread.currentThread().getContextClassLoader() *
  • Using the basic Class.forName() *
  • From ClassLoaderUtil.class.getClassLoader() *
  • From the callingClass.getClassLoader() *
* * @param className The name of the class to load * @param callingClass The Class object of the calling object * @throws ClassNotFoundException If the class cannot be found anywhere. */ public static Class loadClass(String className, Class callingClass) throws ClassNotFoundException { try { ClassLoader cl = Thread.currentThread().getContextClassLoader(); if (cl != null) { return cl.loadClass(className); } } catch (ClassNotFoundException e) { //ignore } return loadClass2(className, callingClass); } public static Class loadClass(String className, Class callingClass, Class type) throws ClassNotFoundException { try { ClassLoader cl = Thread.currentThread().getContextClassLoader(); if (cl != null) { return cl.loadClass(className).asSubclass(type); } } catch (ClassNotFoundException e) { //ignore } return loadClass2(className, callingClass).asSubclass(type); } private static Class loadClass2(String className, Class callingClass) throws ClassNotFoundException { try { return Class.forName(className); } catch (ClassNotFoundException ex) { try { if (ClassLoaderUtils.class.getClassLoader() != null) { return ClassLoaderUtils.class.getClassLoader().loadClass(className); } } catch (ClassNotFoundException exc) { if (callingClass != null && callingClass.getClassLoader() != null) { return callingClass.getClassLoader().loadClass(className); } } throw ex; } } }




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