/*

  * 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.myfaces.taglib.core;

 import javax.el.ELException;

 import javax.el.ValueExpression;

 import javax.faces.component.UIComponent;

 import javax.faces.context.FacesContext;

 import javax.faces.webapp.UIComponentClassicTagBase;

 import javax.faces.webapp.UIComponentELTag;

 import javax.servlet.jsp.JspException;

 import javax.servlet.jsp.tagext.Tag;

 import javax.servlet.jsp.tagext.TagSupport;

 import org.apache.myfaces.shared.util.ClassUtils;

 /**

  * @author Andreas Berger (latest modification by $Author$)

  * @version $Revision$ $Date$

  * @since 1.2

  */

 public abstract class GenericListenerTag<_Holder, _Listener> extends TagSupport

 {

     private ValueExpression _type = null;

     private ValueExpression _binding = null;

     private Class<_Holder> _holderClazz;

     protected GenericListenerTag(Class<_Holder> holderClazz)

     {

         super();

         _holderClazz = holderClazz;

     }

     public void setType(ValueExpression type)

     {

         _type = type;

     }

     public void setBinding(ValueExpression binding)

     {

         _binding = binding;

     }

     @Override

     public void release()

     {

         super.release();

         _type = null;

         _binding = null;

     }

     protected abstract void addListener(_Holder holder, _Listener listener);

     protected abstract _Listener createDelegateListener(ValueExpression type, ValueExpression binding);

     @Override

     @SuppressWarnings("unchecked")

     public int doStartTag() throws JspException

     {

         UIComponentClassicTagBase componentTag = UIComponentELTag.getParentUIComponentClassicTagBase(pageContext);

         if (componentTag == null)

         {

             throw new JspException("no parent UIComponentTag found");

         }

         if (_type == null && _binding == null)

         {

             throw new JspException("\"actionListener\" must have binding and/or type attribute.");

         }

         if (!componentTag.getCreated())

         {

             return Tag.SKIP_BODY;

         }

         _Holder holder = null;

         UIComponent component = componentTag.getComponentInstance();

         try

         {

             holder = (_Holder)component;

         }

         catch (ClassCastException e)

         {

             throw new JspException("Component " + ((UIComponent)holder).getId() + " is not instance of "

                     + _holderClazz.getName());

         }

         if (_type != null && _type.isLiteralText())

         {

             createListener(holder, component);

         }

         else

         {

             addListener(holder, createDelegateListener(_type, _binding));

         }

         return Tag.SKIP_BODY;

     }

     @SuppressWarnings("unchecked")

     protected void createListener(_Holder holder, UIComponent component) throws JspException

     {

         FacesContext facesContext = FacesContext.getCurrentInstance();

         _Listener listener;

         // type and/or binding must be specified

         try

         {

             if (null != _binding)

             {

                 try

                 {

                     listener = (_Listener)_binding.getValue(facesContext.getELContext());

                     if (null != listener)

                     {

                         addListener(holder, listener);

                         // no need for further processing

                         return;

                     }

                 }

                 catch (ELException e)

                 {

                     throw new JspException("Exception while evaluating the binding attribute of Component "

                             + component.getId(), e);

                 }

             }

             if (null != _type)

             {

                 String className;

                 if (_type.isLiteralText())

                 {

                     className = _type.getExpressionString();

                     // If type is literal text we should create

                     // a new instance

                     listener = (_Listener)ClassUtils.newInstance(className);

                 }

                 else

                 {

                     className = (String)_type.getValue(facesContext.getELContext());

                     listener = null;

                 }

                 if (null != _binding)

                 {

                     try

                     {

                         _binding.setValue(facesContext.getELContext(), listener);

                     }

                     catch (ELException e)

                     {

                         throw new JspException("Exception while evaluating the binding attribute of Component "

                                 + component.getId(), e);

                     }

                 }

                 else

                 {

                     // Type is a EL expression, and there is

                     // no binding property so we should create

                     // a new instance

                     listener = (_Listener)ClassUtils.newInstance(className);

                 }

                 addListener(holder, listener);

             }

         }

         catch (ClassCastException e)

         {

             throw new JspException(e);

         }

     }

 }