/*

  * 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.webapp;

 import javax.faces.FacesException;

 import javax.servlet.ServletContext;

 import org.apache.myfaces.buildtools.maven2.plugin.builder.annotation.JSFWebConfigParam;

 import org.apache.myfaces.shared.config.MyfacesConfig;

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

 import org.apache.myfaces.util.ContainerUtils;

 /**

  * Simple Factory to get a FacesInitializer implementation either from a web.xml

  * parameter or from a list of default implementations.

  * 

  * @author Jakob Korherr (latest modification by $Author$)

  * @version $Revision$ $Date$

  */

 public class FacesInitializerFactory

 {

     /**

      * Indicate the class implementing FacesInitializer interface that will

      * be used to setup MyFaces Core contexts.

      * <p>This is used when some custom task must be done specifically when

      * a myfaces web context is initialized or destroyed, or when MyFaces should

      * be initialized in some custom environment. 

      * </p>

      */

     @JSFWebConfigParam(since = "2.0.1", desc = "Class name of a custom FacesInitializer implementation.")

     private static final String FACES_INITIALIZER_PARAM = "org.apache.myfaces.FACES_INITIALIZER";

     /**

      * Gets the FacesInitializer for the system.

      * @param context

      * @return

      */

     public static FacesInitializer getFacesInitializer(ServletContext context)

     {

         FacesInitializer initializer = _getFacesInitializerFromInitParam(context);

         if (initializer == null)

         {

             initializer = _getDefaultFacesInitializer(context);

         }

         return initializer;

     }

     /**

      * Gets a FacesInitializer from the web.xml config param.

      * @param context

      * @return

      */

     private static FacesInitializer _getFacesInitializerFromInitParam(ServletContext context)

     {

         String initializerClassName = context.getInitParameter(FACES_INITIALIZER_PARAM);

         if (initializerClassName != null)

         {

             try

             {

                 // get Class object

                 Class<?> clazz = ClassUtils.classForName(initializerClassName);

                 if (!FacesInitializer.class.isAssignableFrom(clazz))

                 {

                     throw new FacesException("Class " + clazz 

                             + " does not implement FacesInitializer");

                 }

                 // create instance and return it

                 return (FacesInitializer) ClassUtils.newInstance(clazz);

             }

             catch (ClassNotFoundException cnfe)

             {

                 throw new FacesException("Could not find class of specified FacesInitializer", cnfe);

             }

         }

         return null;

     }

     /**

      * Returns a FacesInitializer that fits for the current environment (JSP 2.0 or 2.1).

      * @param context

      * @return

      */

     private static FacesInitializer _getDefaultFacesInitializer(ServletContext context)

     {

         // No MyfacesConfig available yet, we must read the parameter directly:

         String initParameter = context.getInitParameter(MyfacesConfig.INIT_PARAM_SUPPORT_JSP_AND_FACES_EL);

         if (Boolean.FALSE.toString().equals(initParameter))

         {

             return new FaceletsInitilializer();

         } 

         else if (ContainerUtils.isJsp21(context)) 

         {

             return new Jsp21FacesInitializer();

         } 

         else 

         {

             return new Jsp20FacesInitializer();

         }

     }

 }