/*

  * $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);

         }

     }

 }