/*

  * 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.onami.autobind.utils;

 import com.google.common.base.Optional;

 public final class ClassLoadingUtils {

     private ClassLoadingUtils() {

         //Utility Class

     }

     /**

      * Load a class from the current class loader or the thread context class loader.

      * The default behavior is to load the class using the class loader of ClassLoadingUtils and falls back

      * to the thread context class loader if the class was not found.

      * @param className

      * @return

      * @throws ClassNotFoundException

      */

     public static Class loadClass(String className) throws ClassNotFoundException {

         Optional<ClassLoader> currentCloassLoader = Optional.of(ClassLoadingUtils.class.getClassLoader());

         Optional<ClassLoader> threadContextClassLoader = Optional.<ClassLoader>fromNullable(Thread.currentThread().getContextClassLoader());

         Optional<Class> clazz = tryLoad(className, currentCloassLoader).or(tryLoad(className, threadContextClassLoader));

         if (!clazz.isPresent()) {

             throw new ClassNotFoundException("Could not load class:" + className);

         } else {

             return clazz.get();

         }

     }

     /**

      * Try loading a {@link Class} with specified name from the specified {@link ClassLoader}.

      *

      * @param className   The name of the class.

      * @param classLoader The class loader.

      * @return Returns an Optional class.

      */

     private static Optional<Class> tryLoad(String className, Optional<ClassLoader> classLoader) {

         if (!classLoader.isPresent()) {

             return Optional.absent();

         } else {

             try {

                 return Optional.<Class>of(classLoader.get().loadClass(className));

             } catch (ClassNotFoundException ex) {

                 return Optional.absent();

             }

         }

     }

 }