2009/05/20 - Apache Shale has been retired.

   /*
    * 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.shale.util;
  
  import java.beans.BeanInfo;
  import java.beans.IntrospectionException;
  import java.beans.Introspector;
  import java.beans.PropertyDescriptor;
  import java.lang.reflect.InvocationTargetException;
  import java.lang.reflect.Method;
  import javax.faces.el.EvaluationException;
  import javax.faces.el.PropertyNotFoundException;
  
  /***
   * <p>Helper class to provide access to the properties of JavaBeans.  This
   * implementation is stateless and maintains no cached information, so
   * instances may be freely created and destroyed, with no side effects
   * (unless there are side effects from caching inside the JDK itself).</p>
   *
   * $Id: PropertyHelper.java 464373 2006-10-16 04:21:54Z rahul $
   *
   * @since 1.0.1
   */
  public class PropertyHelper {
  
  
      // ---------------------------------------------------------- Public Methods
  
  
      /***
       * <p>Return the value of the specified property from the specified bean.</p>
       *
       * @param bean Bean whose property is to be retrieved
       * @param name Name of the property to get
       *
       * @exception PropertyNotFoundException if the bean class does not have
       *  a property with the specified name, or if the property is write only
       * @exception EvaluationException if an exception occurs while
       *  retrieving the property value
       */
      public Object getValue(Object bean, String name) {
  
          PropertyDescriptor descriptor = descriptor(bean, name);
          Method method = descriptor.getReadMethod();
          if (method == null) {
              throw new PropertyNotFoundException(name);
          }
  
          try {
              return method.invoke(bean, new Object[0]);
          } catch (InvocationTargetException e) {
              throw new EvaluationException(e.getCause());
          } catch (Exception e) {
              throw new EvaluationException(e);
          }
  
      }
  
  
      /***
       * <p>Return <code>true</code> if the specified property is read only on
       * the underlying bean class.</p>
       *
       * @param bean Bean whose property is to be checked
       * @param name Name of the property to check
       *
       * @exception PropertyNotFoundException if the bean class does not have
       *  a property with the specified name, or if the property is write only
       * @exception EvaluationException if an exception occurs while
       *  checking the read only status
       */
      public boolean isReadOnly(Object bean, String name) {
  
          PropertyDescriptor descriptor = descriptor(bean, name);
          if (descriptor.getReadMethod() != null) {
              return descriptor.getWriteMethod() == null;
          }
          throw new PropertyNotFoundException(name);
  
      }
  
  
      /***
       * <p>Return the type of the specified property on the underlying bean
      * class.</p>
      *
      * @param bean Bean whose property is to be analyzed
      * @param name Name of the property to return the type of
      *
      * @exception PropertyNotFoundException if the bean class does not have
      *  a property with the specified name
      * @exception EvaluationException if an exception occurs while
      *  retrieving the property type
      */
     public Class getType(Object bean, String name) {
 
         PropertyDescriptor descriptor = descriptor(bean, name);
         return descriptor.getPropertyType();
 
     }
 
 
     /***
      * <p>Set the specified value on the specified property of the specified
      * bean.</p>
      *
      * @param bean Bean whose property is to be set
      * @param name Name of the property to be set
      * @param value New value for this property
      *
      * @exception PropertyNotFoundException if the bean class does not have
      *  a property with the specified name, or if the property is read only
      * @exception EvaluationException if an exception occurs while
      *  setting the property value
      */
     public void setValue(Object bean, String name, Object value) {
 
         PropertyDescriptor descriptor = descriptor(bean, name);
         Method method = descriptor.getWriteMethod();
         if (method == null) {
             throw new PropertyNotFoundException(name);
         }
 
         try {
             method.invoke(bean, new Object[] { value });
         } catch (InvocationTargetException e) {
             throw new EvaluationException(e.getCause());
         } catch (Exception e) {
             throw new EvaluationException(e);
         }
 
     }
 
 
     // ------------------------------------------------------- Private Methods
 
 
     /***
      * <p>Return the <code>PropertyDescriptor</code> for the specified
      * property of the specified class.</p>
      *
      * @param bean Bean whose property descriptor is to be returned
      * @param name Name of the property to retrieve a descrpitor for
      *
      * @exception PropertyNotFoundException if the bean class does not have
      *  a property with the specified name
      * @exception EvaluationException if an exception occurs introspecting
      *  the underlying bean class
      */
     private PropertyDescriptor descriptor(Object bean, String name) {
 
         BeanInfo beanInfo = null;
         try {
             beanInfo = Introspector.getBeanInfo(bean.getClass());
         } catch (IntrospectionException e) {
             throw new EvaluationException(e);
         }
 
         PropertyDescriptor descriptors[] = beanInfo.getPropertyDescriptors();
         if (descriptors == null) {
             descriptors = new PropertyDescriptor[0];
         }
         for (int i = 0; i < descriptors.length; i++) {
             if (name.equals(descriptors[i].getName())) {
                 return descriptors[i];
             }
         }
 
         throw new PropertyNotFoundException(name);
 
     }
 
 
 }