content: /*
   * Loader.java January 2010
   *
   * Copyright (C) 2010, Niall Gallagher <niallg@users.sf.net>
   *
   * Licensed 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.aliyun.odps.simpleframework.xml.strategy;
  
  /**
   * The <code>Loader</code> object is used to provide class loading
   * for the strategies. This will attempt to load the class using
   * the thread context class loader, if this loader is set it will
   * be used to load the class. If not then the class will be loaded
   * using the caller class loader. Loading in this way ensures 
   * that a custom loader can be provided using the current thread.
   * 
   * @author Niall Gallagher
   */
  class Loader {
     
     /**
      * This method is used to acquire the class of the specified name.
      * Loading is performed by the thread context class loader as this
      * will ensure that the class loading strategy can be changed as
      * requirements dictate. Typically the thread context class loader
      * can handle all serialization requirements.
      * 
      * @param type this is the name of the class that is to be loaded
      * 
      * @return this returns the class that has been loaded by this
      */
     public Class load(String type) throws Exception {
        ClassLoader loader = getClassLoader();
        
        if(loader == null) {
           loader = getCallerClassLoader();
        }
        return loader.loadClass(type);      
     }
     
     /**
      * This is used to acquire the caller class loader for this object.
      * Typically this is only used if the thread context class loader
      * is set to null. This ensures that there is at least some class
      * loader available to the strategy to load the class.
      * 
      * @return this returns the loader that loaded this class     
      */
     private static ClassLoader getCallerClassLoader() throws Exception {
        return Loader.class.getClassLoader();
     }
  
     /**
      * This is used to acquire the thread context class loader. This
      * is the default class loader used by the cycle strategy. When
      * using the thread context class loader the caller can switch the
      * class loader in use, which allows class loading customization.
      * 
      * @return this returns the loader used by the calling thread
      */
     private static ClassLoader getClassLoader() throws Exception {
        return Thread.currentThread().getContextClassLoader();
     }
     
  }
  