/*
    * $Id: VelocityRenderer.java 1306435 2012-03-28 15:39:11Z nlebas $
    *
    * 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.tiles.request.velocity.render;
  
  import java.io.IOException;
  
  import org.apache.tiles.request.Request;
  import org.apache.tiles.request.render.CannotRenderException;
  import org.apache.tiles.request.render.Renderer;
  import org.apache.tiles.request.servlet.ServletRequest;
  import org.apache.tiles.request.servlet.ServletUtil;
  import org.apache.velocity.Template;
  import org.apache.velocity.context.Context;
  import org.apache.velocity.tools.view.VelocityView;
  
  /**
   * Attribute renderer for rendering Velocity templates as attributes. <br>
   * It is available only to Servlet-based environment.<br>
   * It uses {@link VelocityView} to render the response.<br>
   * To initialize it correctly, call {@link #setParameter(String, String)} for
   * all the parameters that you want to set, and then call {@link #commit()}.
   *
   * @version $Rev: 1306435 $ $Date: 2012-03-29 02:39:11 +1100 (Thu, 29 Mar 2012) $
   */
  public class VelocityRenderer implements Renderer {
  
      /**
       * The VelocityView object to use.
       */
      private VelocityView velocityView;
  
      /**
       * Constructor.
       *
       * @param velocityView The Velocity view manager.
       */
      public VelocityRenderer(VelocityView velocityView) {
          this.velocityView = velocityView;
      }
  
      /** {@inheritDoc} */
      @Override
      public void render(String path, Request request) throws IOException {
          if (path == null) {
              throw new CannotRenderException("Cannot dispatch a null path");
          }
  
          ServletRequest servletRequest = ServletUtil.getServletRequest(request);
          // then get a context
          Context context = velocityView.createContext(servletRequest
                  .getRequest(), servletRequest.getResponse());
  
          // get the template
          Template template = velocityView.getTemplate((String) path);
  
          // merge the template and context into the writer
          velocityView.merge(template, context, request.getWriter());
      }
  
      /** {@inheritDoc} */
      public boolean isRenderable(String path, Request request) {
          return path != null && path.startsWith("/") && path.endsWith(".vm");
      }
  }