/*
    * $Id: DefinitionDispatcherAction.java 471754 2006-11-06 14:55:09Z husted $
    *
    * 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.struts.tiles.actions;
  
  import java.io.IOException;
  import java.io.PrintWriter;
  
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.struts.action.Action;
  import org.apache.struts.action.ActionForm;
  import org.apache.struts.action.ActionForward;
  import org.apache.struts.action.ActionMapping;
  import org.apache.struts.tiles.ComponentDefinition;
  import org.apache.struts.tiles.DefinitionsFactoryException;
  import org.apache.struts.tiles.DefinitionsUtil;
  import org.apache.struts.tiles.FactoryNotFoundException;
  import org.apache.struts.tiles.NoSuchDefinitionException;
  import org.apache.struts.tiles.TilesUtil;
  
  /**
   * <p>An <strong>Action</strong> that dispatches to a Tiles Definition
   * that is named by the request parameter whose name is specified
   * by the <code>parameter</code> property of the corresponding
   * ActionMapping.
   * This action is useful in following situations:
   * <li>
   * <ul>To associate an Url to a definition</ul>
   * <ul>To use Struts &lt;html:link&gt; tag on a definition</ul>
   * </li>
   * <p>To configure the use of this action in your
   * <code>struts-config.xml</code> file, create an entry like this:</p>
   *
   * <code>
   *   &lt;action path="/saveSubscription"
   *           type="org.apache.struts.tiles.actions.DefinitionDispatcherAction"
   *           parameter="def"/&gt;
   *     &lt;forward name="success"   path="anything" //&gt;
   *     &lt;forward name="error"     path="path.to.error.page" //&gt;
   * </code>
   *
   * <p>which will use the value of the request parameter named "def"
   * to pick the appropriate definition name.
   * <p>  The value for success doesn't matter. The forward will forward to
   * appropriate definition.
   * <p> The value for error should denote a valid jsp path or definition name.
   *
   * @version $Rev: 471754 $ $Date: 2006-11-06 08:55:09 -0600 (Mon, 06 Nov 2006) $
   */
  public class DefinitionDispatcherAction extends Action {
  
      /**
       * Commons Logging instance.
       */
      protected static Log log = LogFactory.getLog(DefinitionDispatcherAction.class);
  
      /**
       * Process the specified HTTP request, and create the corresponding HTTP
       * response (or forward to another web component that will create it),
       * with provision for handling exceptions thrown by the business logic.
       *
       * @param mapping The ActionMapping used to select this instance
       * @param form The optional ActionForm bean for this request (if any)
       * @param request The HTTP request we are processing
       * @param response The HTTP response we are creating
       *
       * @exception Exception if the application business logic throws
       *  an exception
       * @since Struts 1.1
       */
      public ActionForward execute(
          ActionMapping mapping,
          ActionForm form,
          HttpServletRequest request,
          HttpServletResponse response)
          throws Exception {
  
         // Identify the request parameter containing the method name
         // If none defined, use "def"
         String parameter = mapping.getParameter();
         if (parameter == null) {
             parameter = "def";
         }
 
         // Identify the method name to be dispatched to
         String name = request.getParameter(parameter);
         if (name == null) {
             log.error("Can't get parameter '" + parameter + "'.");
 
             return mapping.findForward("error");
         }
 
         // Try to dispatch to requested definition
         try {
             // Read definition from factory, but we can create it here.
             ComponentDefinition definition =
                 TilesUtil.getDefinition(
                     name,
                     request,
                     getServlet().getServletContext());
 
             if (log.isDebugEnabled()) {
                 log.debug("Get Definition " + definition);
             }
 
             DefinitionsUtil.setActionDefinition(request, definition);
 
         } catch (FactoryNotFoundException e) {
             log.error("Can't get definition factory.", e);
             return mapping.findForward("error");
 
         } catch (NoSuchDefinitionException e) {
             log.error("Can't get definition '" + name + "'.", e);
             return mapping.findForward("error");
 
         } catch (DefinitionsFactoryException e) {
             log.error("General Factory error '" + e.getMessage() + "'.", e);
             return mapping.findForward("error");
 
         } catch (Exception e) {
             log.error("General error '" + e.getMessage() + "'.", e);
             return mapping.findForward("error");
         }
 
         return mapping.findForward("success");
 
     }
 
     /**
      * @deprecated This will be removed after Struts 1.2.
      */
     protected void printError(HttpServletResponse response, String msg)
         throws IOException {
         response.setContentType("text/plain");
         PrintWriter writer = response.getWriter();
         writer.println(msg);
         writer.flush();
         writer.close();
     }
 }