package com.opensymphony.module.sitemesh.util;import java.net.URL;import java.io.InputStream;import java.io.IOException;/** * This class is extremely useful for loading resources and classes in a fault tolerant manner * that works across different applications servers. * * It has come out of many months of frustrating use of multiple application servers at Atlassian, * please don't change things unless you're sure they're not going to break in one server or another! */public class ClassLoaderUtil {      /**    * Load a given resource.    *    * This method will try to load the resource using the following methods (in order):    * <ul>    *  <li>From Thread.currentThread().getContextClassLoader()    *  <li>From ClassLoaderUtil.class.getClassLoader()    *  <li>callingClass.getClassLoader()    * </ul>    *    * @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) {            url = ClassLoaderUtil.class.getClassLoader().getResource(resourceName);        }        if (url == null) {            ClassLoader cl = callingClass.getClassLoader();            if (cl != null) {                url = cl.getResource(resourceName);            }        }        if ((url == null) && (resourceName != null) && (resourceName.charAt(0) != '/')) {            return getResource('/' + resourceName, callingClass);        }        return url;    }    /**    * 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:    * <ul>    *  <li>From Thread.currentThread().getContextClassLoader()    *  <li>Using the basic Class.forName()    *  <li>From ClassLoaderUtil.class.getClassLoader()    *  <li>From the callingClass.getClassLoader()    * </ul>    *    * @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 {            return Thread.currentThread().getContextClassLoader().loadClass(className);        } catch (ClassNotFoundException e) {            try {                return Class.forName(className);            } catch (ClassNotFoundException ex) {                try {                    return ClassLoaderUtil.class.getClassLoader().loadClass(className);                } catch (ClassNotFoundException exc) {                    return callingClass.getClassLoader().loadClass(className);                }            }        }    }}