/*
    * Copyright 2002,2004 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.commons.jelly.tags.define;
  
  import java.lang.reflect.Method;
  import java.util.HashMap;
  import java.util.Map;
  
  import org.apache.commons.jelly.JellyTagException;
  import org.apache.commons.jelly.MissingAttributeException;
  import org.apache.commons.jelly.Tag;
  import org.apache.commons.jelly.XMLOutput;
  import org.apache.commons.jelly.impl.Attribute;
  import org.apache.commons.jelly.impl.DynamicBeanTag;
  import org.apache.commons.jelly.impl.TagFactory;
  import org.apache.commons.jelly.util.ClassLoaderUtils;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  import org.xml.sax.Attributes;
  
  /***
   * Binds a Java bean to the given named Jelly tag so that the attributes of
   * the tag set the bean properties..
   *
   * @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
   * @version $Revision: 155420 $
   */
  public class BeanTag extends DefineTagSupport {
  
      /*** The Log to which logging calls will be made. */
      private static final Log log = LogFactory.getLog(BeanTag.class);
  
      /*** An empty Map as I think Collections.EMPTY_MAP is only JDK 1.3 onwards */
      private static final Map EMPTY_MAP = new HashMap();
  
      /*** the name of the tag to create */
      private String name;
  
      /*** the Java class name to use for the tag */
      private String className;
  
      /*** the ClassLoader used to load beans */
      private ClassLoader classLoader;
  
      /*** the name of the attribute used for the variable name */
      private String varAttribute = "var";
  
      /*** the attribute definitions for this dynamic tag */
      private Map attributes;
  
      /***
       * Adds a new attribute definition to this dynamic tag
       */
      public void addAttribute(Attribute attribute) {
          if ( attributes == null ) {
              attributes = new HashMap();
          }
          attributes.put( attribute.getName(), attribute );
      }
  
      // Tag interface
      //-------------------------------------------------------------------------
      public void doTag(XMLOutput output) throws MissingAttributeException, JellyTagException {
          invokeBody(output);
  
          if (name == null) {
              throw new MissingAttributeException("name");
          }
          if (className == null) {
              throw new MissingAttributeException("className");
          }
  
          Class theClass = null;
          try {
              ClassLoader classLoader = getClassLoader();
              theClass = ClassLoaderUtils.loadClass(className, getClassLoader(), getContext().getUseContextClassLoader(), getClass());
          }
          catch (ClassNotFoundException e) {
              log.error( "Could not load class: " + className + " exception: " + e, e );
              throw new JellyTagException(
                  "Could not find class: "
                      + className
                      + " using ClassLoader: "
                     + classLoader);
         }
 
         final Class beanClass = theClass;
         final Method invokeMethod = getInvokeMethod( theClass );
         final Map beanAttributes = (attributes != null) ? attributes : EMPTY_MAP;
 
         TagFactory factory = new TagFactory() {
             public Tag createTag(String name, Attributes attributes) {
                 return  new DynamicBeanTag(beanClass, beanAttributes, varAttribute, invokeMethod);
             }
         };
 
         getTagLibrary().registerBeanTag(name, factory);
 
         // now lets clear the attributes for next invocation and help the GC
         attributes = null;
     }
 
 
     // Properties
     //-------------------------------------------------------------------------
 
     /***
      * Sets the name of the tag to create
      */
     public void setName(String name) {
         this.name = name;
     }
 
     /***
      * Sets the Java class name to use for the tag
      */
     public void setClassName(String className) {
         this.className = className;
     }
 
     /***
      * Sets the ClassLoader to use to load the class.
      * If no value is set then the current threads context class
      * loader is used.
      */
     public void setClassLoader(ClassLoader classLoader) {
         this.classLoader = classLoader;
     }
 
     /***
      * @return the ClassLoader to use to load classes specified by this object, 
      *  the thread context loader if the context flag is set, or the class used to load this class.
      */
     public ClassLoader getClassLoader() {
         return ClassLoaderUtils.getClassLoader(classLoader, getContext().getUseContextClassLoader(), getClass());
     }
 
     /***
      * Sets the name of the attribute used to define the bean variable that this dynamic
      * tag will output its results as. This defaults to 'var' though this property
      * can be used to change this if it conflicts with a bean property called 'var'.
      */
     public void setVarAttribute(String varAttribute) {
         this.varAttribute = varAttribute;
     }
 
 
     // Implementation methods
     //-------------------------------------------------------------------------
 
     /***
      * Extracts the invoke method for the class if one is used.
      */
     protected Method getInvokeMethod( Class theClass ) {
         return null;
     }
 }