package org.apache.turbine.modules.layouts;

 import javax.servlet.http.HttpServletResponse;

 import org.apache.logging.log4j.LogManager;

 /*

  * 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.

  */

 import org.apache.logging.log4j.Logger;

 import org.apache.turbine.Turbine;

 import org.apache.turbine.annotation.TurbineService;

 import org.apache.turbine.modules.Layout;

 import org.apache.turbine.pipeline.PipelineData;

 import org.apache.turbine.services.velocity.VelocityService;

 import org.apache.turbine.util.RunData;

 import org.apache.velocity.context.Context;

 /**

  * This Layout module allows Velocity templates

  * to be used as layouts.

  *

  * @author <a href="mailto:tv@apache.org">Thomas Vandahl</a>

  */

 public abstract class VelocityLayout implements Layout

 {

     /** Logging */

     protected final Logger log = LogManager.getLogger(this.getClass());

     /** The prefix for lookup up layout pages */

     protected static final String prefix = PREFIX + "/";

     /** Injected service instance */

     @TurbineService

     protected VelocityService velocityService;

     /**

      * Method called by LayoutLoader.

      *

      *

      * @param pipelineData PipelineData

      * @throws Exception generic exception

      */

     @Override

     public void doBuild(PipelineData pipelineData)

         throws Exception

     {

         RunData data = pipelineData.getRunData();

         // Get the context needed by Velocity.

         Context context = velocityService.getContext(pipelineData);

         // Provide objects to Velocity context

         populateContext(pipelineData, context);

         // Grab the layout template set in the VelocityPage.

         // If null, then use the default layout template

         // (done by the TemplateInfo object)

         String templateName = data.getTemplateInfo().getLayoutTemplate();

         // Set the locale and content type

         data.getResponse().setLocale(data.getLocale());

         data.getResponse().setContentType(data.getContentType());

         log.debug("Now trying to render layout {}", templateName);

         // Finally, generate the layout template and send it to the browser

         render(pipelineData, context, templateName);

     }

     /**

      * Populate Velocity context

      *

      * @param pipelineData PipelineData

      * @param context the Velocity context

      *

      * @throws Exception if evaluation fails

      */

     protected abstract void populateContext(PipelineData pipelineData, Context context)

         throws Exception;

     /**

      * Render layout

      *

      * @param pipelineData PipelineData

      * @param context the Velocity context

      * @param templateName relative path to Velocity template

      *

      * @throws Exception if rendering fails

      */

     protected void render(PipelineData pipelineData, Context context, String templateName)

         throws Exception

     {

         velocityService.handleRequest(context,

                 prefix + templateName,

                 pipelineData.get(Turbine.class, HttpServletResponse.class)

                     .getOutputStream());

     }

 }