/*
    * $Id: ClassUtil.java 1306435 2012-03-28 15:39:11Z nlebas $
    *
    * 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.tiles.request.reflect;
  
  import java.beans.BeanInfo;
  import java.beans.Introspector;
  import java.beans.PropertyDescriptor;
  import java.util.Map;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  
  /**
   * Utilities to work with dynamic class loading and instantiation.
   *
   * @version $Rev: 1306435 $ $Date: 2012-03-29 02:39:11 +1100 (Thu, 29 Mar 2012) $
   */
  public final class ClassUtil {
  
      /**
       * Constructor, private to avoid instantiation.
       */
      private ClassUtil() {
      }
  
      /**
       * Returns the class and casts it to the correct subclass.<br>
       * It tries to use the thread's current classloader first and, if it does
       * not succeed, uses the classloader of ClassUtil.
       *
       * @param <T> The subclass to use.
       * @param className The name of the class to load.
       * @param baseClass The base class to subclass to.
       * @return The loaded class.
       * @throws ClassNotFoundException If the class has not been found.
       */
      public static <T> Class<? extends T> getClass(String className,
              Class<T> baseClass) throws ClassNotFoundException {
          ClassLoader classLoader = Thread.currentThread()
                  .getContextClassLoader();
          if (classLoader == null) {
              classLoader = ClassUtil.class.getClassLoader();
          }
          return Class.forName(className, true, classLoader)
                  .asSubclass(baseClass);
      }
  
      /**
       * Returns an instance of the given class name, by calling the default
       * constructor.
       *
       * @param className The class name to load and to instantiate.
       * @return The new instance of the class name.
       * @throws CannotInstantiateObjectException If something goes wrong during
       * instantiation.
       */
      public static Object instantiate(String className) {
          return instantiate(className, false);
      }
  
      /**
       * Returns an instance of the given class name, by calling the default
       * constructor.
       *
       * @param className The class name to load and to instantiate.
       * @param returnNull If <code>true</code>, if the class is not found it
       * returns <code>true</code>, otherwise it throws a
       * <code>TilesException</code>.
       * @return The new instance of the class name.
       * @throws CannotInstantiateObjectException If something goes wrong during instantiation.
       */
      public static Object instantiate(String className, boolean returnNull) {
          ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
          if (classLoader == null) {
              classLoader = ClassUtil.class.getClassLoader();
          }
          try {
              Class<? extends Object> namedClass = getClass(className, Object.class);
              return namedClass.newInstance();
          } catch (ClassNotFoundException e) {
             if (returnNull) {
                 return null;
             }
             throw new CannotInstantiateObjectException(
                     "Unable to resolve factory class: '" + className + "'", e);
         } catch (IllegalAccessException e) {
             throw new CannotInstantiateObjectException(
                     "Unable to access factory class: '" + className + "'", e);
         } catch (InstantiationException e) {
             throw new CannotInstantiateObjectException(
                     "Unable to instantiate factory class: '"
                             + className
                             + "'. Make sure that this class has a default constructor",
                     e);
         }
     }
 
     /**
      * Collects bean infos from a class and filling a list.
      *
      * @param clazz The class to be inspected.
      * @param name2descriptor The map in the form: name of the property ->
      * descriptor.
      */
     public static void collectBeanInfo(Class<?> clazz,
             Map<String, PropertyDescriptor> name2descriptor) {
         Logger log = LoggerFactory.getLogger(ClassUtil.class);
         BeanInfo info = null;
         try {
             info = Introspector.getBeanInfo(clazz);
         } catch (Exception ex) {
             if (log.isDebugEnabled()) {
                 log.debug("Cannot inspect class " + clazz, ex);
             }
         }
         if (info == null) {
             return;
         }
         for (PropertyDescriptor pd : info.getPropertyDescriptors()) {
             pd.setValue("type", pd.getPropertyType());
             pd.setValue("resolvableAtDesignTime", Boolean.TRUE);
             name2descriptor.put(pd.getName(), pd);
         }
     }
 }