/*

  * 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.spi;

 import javax.faces.FacesException;

 import javax.faces.context.ExternalContext;

 import javax.servlet.ServletContext;

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

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

 import org.apache.myfaces.spi.impl.DefaultServiceProviderFinder;

 /**

  * Factory that provide a ServiceProviderFinder instance, that is used to locate

  * classes through SPI interface.  

  * 

  * @author Leonardo Uribe

  * @since 2.0.3

  *

  */

 public class ServiceProviderFinderFactory

 {

     private final static String SERVICE_PROVIDER_KEY = "org.apache.myfaces.spi.ServiceProviderFinder";

     /**

      * Define the class name of a custom ServiceProviderFinder implementation.

      * 

      * <p>This class is used to override the default SPI scanning algorithm, that relies on the thread

      * context class loader to locate entries under META-INF/services folder.

      * </p>

      */

     @JSFWebConfigParam(since = "2.0.3", desc = "Class name of a custom ServiceProviderFinder implementation.")

     private static final String SERVICE_PROVIDER_FINDER_PARAM = "org.apache.myfaces.SERVICE_PROVIDER_FINDER";

     /**

      * 

      * @param ectx

      * @return

      */

     public static ServiceProviderFinder getServiceProviderFinder(ExternalContext ectx)

     {

         ServiceProviderFinder slp = (ServiceProviderFinder) ectx.getApplicationMap().get(SERVICE_PROVIDER_KEY);

         if (slp == null)

         {

             slp = _getServiceProviderFinderFromInitParam(ectx);

             if (slp == null)

             {

                 slp = new DefaultServiceProviderFinder();

             }

             // cache on ApplicationMap

             setServiceProviderFinder(ectx, slp);

         }

         return slp;

     }

     /**

      * Set a ServiceProviderFinder to the current application, to locate 

      * SPI service providers used by MyFaces.  

      * 

      * This method should be called before the web application is initialized,

      * specifically before AbstractFacesInitializer.initFaces(ServletContext)

      * otherwise it will have no effect.

      * 

      * @param ectx

      * @param slp

      */

     public static void setServiceProviderFinder(ExternalContext ectx, ServiceProviderFinder slp)

     {

         ectx.getApplicationMap().put(SERVICE_PROVIDER_KEY, slp);

     }

     public static void setServiceProviderFinder(ServletContext ctx, ServiceProviderFinder slp)

     {

         ctx.setAttribute(SERVICE_PROVIDER_KEY, slp);

     }

     /**

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

      * @param context

      * @return

      */

     private static ServiceProviderFinder _getServiceProviderFinderFromInitParam(ExternalContext context)

     {

         String initializerClassName = context.getInitParameter(SERVICE_PROVIDER_FINDER_PARAM);

         if (initializerClassName != null)

         {

             try

             {

                 // get Class object

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

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

                 {

                     throw new FacesException("Class " + clazz 

                             + " does not implement ServiceProviderFinder");

                 }

                 // create instance and return it

                 return (ServiceProviderFinder) ClassUtils.newInstance(clazz);

             }

             catch (ClassNotFoundException cnfe)

             {

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

             }

         }

         return null;

     }

 }