package org.apache.turbine.modules.screens;
   
   /*
    * 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.commons.lang.StringUtils;
  import org.apache.commons.lang.exception.ExceptionUtils;
  
  import org.apache.ecs.ConcreteElement;
  import org.apache.ecs.StringElement;
  
  import org.apache.velocity.context.Context;
  
  import org.apache.turbine.Turbine;
  import org.apache.turbine.TurbineConstants;
  import org.apache.turbine.services.template.TurbineTemplate;
  import org.apache.turbine.services.velocity.TurbineVelocity;
  import org.apache.turbine.util.RunData;
  
  /***
   * Base Velocity Screen.  The buildTemplate() assumes the template
   * parameter has been set in the RunData object.  This provides the
   * ability to execute several templates from one Screen.
   *
   * <p>
   *
   * If you need more specific behavior in your application, extend this
   * class and override the doBuildTemplate() method.
   *
   * @author <a href="mailto:mbryson@mont.mindspring.com">Dave Bryson</a>
   * @author <a href="mailto:hps@intermeta.de">Henning P. Schmiedehausen</a>
   * @version $Id: VelocityScreen.java 534527 2007-05-02 16:10:59Z tv $
   */
  public class VelocityScreen
      extends TemplateScreen
  {
      /*** The prefix for lookup up screen pages */
      private String prefix = TurbineConstants.SCREEN_PREFIX + "/";
  
      /***
       * Velocity Screens extending this class should overide this
       * method to perform any particular business logic and add
       * information to the context.
       *
       * @param data Turbine information.
       * @param context Context for web pages.
       * @exception Exception, a generic exception.
       */
      protected void doBuildTemplate(RunData data,
                                     Context context)
              throws Exception
      {
      }
  
      /***
       * Needs to be implemented to make TemplateScreen like us.  The
       * actual method that you should override is the one with the
       * context in the parameter list.
       *
       * @param data Turbine information.
       * @exception Exception, a generic exception.
       */
      protected void doBuildTemplate(RunData data)
              throws Exception
      {
          doBuildTemplate(data, TurbineVelocity.getContext(data));
      }
  
      /***
       * This builds the Velocity template.
       *
       * @param data Turbine information.
       * @return A ConcreteElement.
       * @exception Exception, a generic exception.
       */
      public ConcreteElement buildTemplate(RunData data)
          throws Exception
      {
          String screenData = null;
  
          Context context = TurbineVelocity.getContext(data);
  
          String screenTemplate = data.getTemplateInfo().getScreenTemplate();
         String templateName
             = TurbineTemplate.getScreenTemplateName(screenTemplate);
 
         // The Template Service could not find the Screen
         if (StringUtils.isEmpty(templateName))
         {
             log.error("Screen " + screenTemplate + " not found!");
             throw new Exception("Could not find screen for " + screenTemplate);
         }
 
         try
         {
             // if a layout has been defined return the results, otherwise
             // send the results directly to the output stream.
             if (getLayout(data) == null)
             {
                 TurbineVelocity.handleRequest(context,
                         prefix + templateName,
                         data.getResponse().getOutputStream());
             }
             else
             {
                 screenData = TurbineVelocity
                         .handleRequest(context, prefix + templateName);
             }
         }
         catch (Exception e)
         {
             // If there is an error, build a $processingException and
             // attempt to call the error.vm template in the screens
             // directory.
             context.put (TurbineConstants.PROCESSING_EXCEPTION_PLACEHOLDER, e.toString());
             context.put (TurbineConstants.STACK_TRACE_PLACEHOLDER, ExceptionUtils.getStackTrace(e));
 
             templateName = Turbine.getConfiguration()
                 .getString(TurbineConstants.TEMPLATE_ERROR_KEY,
                            TurbineConstants.TEMPLATE_ERROR_VM);
 
             screenData = TurbineVelocity.handleRequest(
                 context, prefix + templateName);
         }
 
         // package the response in an ECS element
         StringElement output = new StringElement();
         output.setFilterState(false);
 
         if (screenData != null)
         {
             output.addElement(screenData);
         }
         return output;
     }
 
     /***
      * Return the Context needed by Velocity.
      *
      * @param data Turbine information.
      * @return A Context.
      *
      * @deprecated Use TurbineVelocity.getContext(data)
      */
     public static Context getContext(RunData data)
     {
         return TurbineVelocity.getContext(data);
     }
 }