/*

 * reserved comment block

 * DO NOT REMOVE OR ALTER!

 */

/**

 * 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 com.sun.org.apache.xml.internal.security.utils;

/**

 * This class is extremely useful for loading 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.

 */

final class ClassLoaderUtils {

    private static final com.sun.org.slf4j.internal.Logger LOG =

        com.sun.org.slf4j.internal.LoggerFactory.getLogger(ClassLoaderUtils.class);

    private ClassLoaderUtils() {

    }

    /**

     * Load a class with a given name. <p></p> 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.

     */

    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) {

            LOG.debug(e.getMessage(), e);

            //ignore

        }

        return loadClass2(className, callingClass);

    }

    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);

                }

            }

            LOG.debug(ex.getMessage(), ex);

            throw ex;

        }

    }

}