/*
    * Copyright 2001-2004 The Apache Software Foundation.
    * 
    * 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 org.apache.juddi.util;
  
  import java.io.InputStream;
  import java.lang.reflect.InvocationTargetException;
  import java.lang.reflect.Method;
  import java.net.URL;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  /***
   * The idea for most of this code was taken from the Apache
   * (Jakarta) Log4j project: http://jakarta.apache.org/log4j
   *
   *  - Steve
   *
   * @author Ceki Gülcü
   * @author anou_mana;
  */
  public class Loader
  {
    // private reference to the jUDDI logger
    private static Log log = LogFactory.getLog(Loader.class);
    /***
     * Added for unittesting with maven
     * 
     * @param resource
     * @return
     */
    public InputStream getResourceAsStreamFromClass(String resource) {
        InputStream stream = getClass().getClassLoader().getResourceAsStream(resource);
        return stream;
    }
    /***
     * @param resource
     * @return InputStream to the named resource
     */
    public static InputStream getResourceAsStream(String resource)
    {
      ClassLoader classLoader = null;
      InputStream stream = null;
  
      // Get the Thread Context Class Loader which is
      // only available in JDK 1.2 and later.
      try
      {
        classLoader = getContextClassLoader();
        if (classLoader != null)
        {
          log.debug("Trying to find ["+resource+"] using context classloader "+classLoader+".");
          stream = classLoader.getResourceAsStream(resource);
          if(stream != null) {
            return stream;
          }
        }
  
        // We could not find resource. Ler us now try
        // with the class loader that loaded this class.
        classLoader = Loader.class.getClassLoader();
        if (classLoader != null)
        {
          log.debug("Trying to find ["+resource+"] using "+classLoader+" class loader.");
          stream = classLoader.getResourceAsStream(resource);
          if(stream != null) {
            return stream;
          }
        }
      }
      catch(Throwable th) {
        log.warn("Exception thrown from Loader.getResource(\""+resource+"\").",th);
      }
  
      // Last ditch attempt: get the resource from the class path. It
      // may be the case that class was loaded by the Extentsion class
      // loader which the parent of the system class loader.
      log.debug("Trying to find ["+resource+"] using ClassLoader.getSystemResource().");
  
      return ClassLoader.getSystemResourceAsStream(resource);
    }
  
    /***
     * @param resource name
     * @return URL to the named resource
     */
   public static URL getResource(String resource)
   {
     ClassLoader classLoader = null;
     URL url = null;
 
     // Get the Thread Context Class Loader which is
     // only available in JDK 1.2 and later.
     try
     {
       classLoader = getContextClassLoader();
       if (classLoader != null)
       {
         log.debug("Trying to find ["+resource+"] using context classloader "+classLoader+".");
         url = classLoader.getResource(resource);
         if(url != null) {
           return url;
         }
       }
 
       // We could not find resource. Ler us now try
       // with the class loader that loaded this class.
       classLoader = Loader.class.getClassLoader();
       if (classLoader != null)
       {
         log.debug("Trying to find ["+resource+"] using "+classLoader+" class loader.");
         url = classLoader.getResource(resource);
         if(url != null) {
           return url;
         }
       }
     }
     catch(Throwable th) {
       log.warn("Exception thrown from Loader.getResource(\""+resource+"\").",th);
     }
 
     // Last ditch attempt: get the resource from the class path. It
     // may be the case that class was loaded by the Extentsion class
     // loader which the parent of the system class loader.
     log.debug("Trying to find ["+resource+"] using ClassLoader.getSystemResource().");
 
     return ClassLoader.getSystemResource(resource);
   }
 
   /***
    * Get the Thread Context Class Loader which is only available
    * in JDK 1.2 and later.
    * @return null if running under a JDK that's earlier than 1.2
    **/
   private static ClassLoader getContextClassLoader()
     throws IllegalAccessException, InvocationTargetException
   {
     Method method = null;
     try {
       method = Thread.class.getMethod("getContextClassLoader",(Class[])null);
     }
     catch (NoSuchMethodException e) {
       return null; // Using JDK 1.1 or earlier
     }
 
     return (ClassLoader)method.invoke(Thread.currentThread(),(Object[])null);
   }
 
   /***
    * 
    * @param name
    * @return The class object for the name given
    * @throws ClassNotFoundException
    * @throws NoClassDefFoundError
    */
   public static Class getClassForName(String name)
     throws ClassNotFoundException, NoClassDefFoundError
   {
     Class clazz = null;
 
     try
     {
       log.info("Using the Context ClassLoader");
       ClassLoader ccl = Thread.currentThread().getContextClassLoader();
       clazz = Class.forName(name, true, ccl);
     }
     catch (Exception e)
     {
       log.warn("Failed to load the class " + name + " with context class loader " + e);
     }
 
     if (null == clazz)
     {
       ClassLoader scl = ClassLoader.getSystemClassLoader();
       try
       {
         log.info("Using the System ClassLoader");
         clazz = Class.forName(name, true, scl);
       }
       catch (Exception e)
       {
         log.warn("Failed to load the class " + name + " with system class loader " + e);
       }
     }
 
     return clazz;
   }
 }