struts-sandbox/tiles-documentation/src/java/org/apache/struts/webapp/tiles/skin/LayoutSwitchAction.java

/*
 * $Id$ 
 *
 * Copyright 1999-2004 The Apache Software Foundation.
 * 
 * Licensed 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.webapp.tiles.skin;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
import org.apache.struts.tiles.ComponentContext;
import org.apache.struts.tiles.ComponentDefinition;
import org.apache.struts.tiles.DefinitionsFactoryException;
import org.apache.struts.tiles.actions.TilesAction;

  /**
   * Customize layouts according to predefined "skin"
   * A "skin" is a set of layouts used together to provide a consistent
   * Look & Feel.
   * This action is called when inserting a definition's layout. It replaces
   * definition's layout by the one set in selected skin.
   * the appropriate
   * Available skins are stored in application context. They are initialized from
   * a Tile definition.
   * Currently selected skin is stored under user session, if any. Otherwise,
   * the default skin is used.
   * This action act for all layouts. A Tile's attribute (skinLayout) is used as a key to
   * know which layouts is concerned.
   */
public class LayoutSwitchAction extends TilesAction
{
    /** debug flag */
  public static boolean debug = true;
    /** Tile's attribute containing layout key */
  public static final String LAYOUT_ATTRIBUTE = "layout.attribute";
    /** Tile attribute containing name used to store user settings in session context */
  public static String USER_SETTINGS_NAME_ATTRIBUTE = "userSettingsName";
    /** Default name used to store settings in session context */
  public static String DEFAULT_USER_SETTINGS_NAME = "examples.tiles.skin.SELECTED_DEFINITION";

    /** Name of catalog in application context */
  public static final String CATALOG_NAME = "examples.tiles.skin.CATALOG_NAME";

    /** Default name used to store menu catalog in application scope */
  public static String DEFAULT_CATALOG_NAME = "tiles.examples.skin.layoutCatalog";
    /** Tile attribute containing name used to store menu catalog in application scope */
  public static String CATALOG_NAME_ATTRIBUTE = "catalogName";
    /** Tile attribute containing name of the settings definition used to initialize catalog */
  public static final String CATALOG_SETTING_ATTRIBUTE = "catalogSettings";

    /**
     * Process the specified HTTP request, and create the corresponding HTTP
     * response (or forward to another web component that will create it).
     * Return an <code>ActionForward</code> instance describing where and how
     * control should be forwarded, or <code>null</code> if the response has
     * already been completed.
     * This method should be implemented by subclasses.
     *
     * @param context The current Tile context, containing Tile attributes.
     * @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(
        ComponentContext context,
        ActionMapping mapping,
        ActionForm form,
        HttpServletRequest request,
        HttpServletResponse response)
        throws Exception
    {
    if(debug)
      System.out.println( "EnterLayoutSwitchAction"  );
      // Get attribute value indicating which layout we want
    String layoutKey = (String)context.getAttribute( LAYOUT_ATTRIBUTE );
    if(layoutKey==null)
      throw new ServletException( "Error - CustomSkinAction : attribute '"
                                  + LAYOUT_ATTRIBUTE
                                  + "' not found in Tile's attributes. Need it to select appropriate layout"  );

      // Get user current skin
    ComponentDefinition definition = getCurrentDefinition( context, request, getServlet().getServletContext() );
      // get requested layout from definition
    String layout = (String)definition.getAttribute(layoutKey);
    if(layout==null)
      throw new ServletException( "Error - CustomSkinAction : no layout defined for key '"
                                  + layoutKey
                                  + "' in currently selected skin '"
                                  + getUserSetting(context, request ) + "'."  );
      // set path to forward to
      // Not very nice solution, need to improve it
    /*
    ComponentDefinition forwarDefinition = new ComponentDefinition( "", layout, new HashMap() );
    DefinitionsUtil.setActionDefinition( request, forwarDefinition );
    */
    if(debug)
      System.out.println( "Switch to : " + layout  );
    RequestDispatcher rd = getServlet().getServletContext().getRequestDispatcher( layout );
    if(rd==null)
      throw new ServletException( "LayoutSwitch error : Can't find layout '"
                                  + layout + "'." );
    rd.include(request, response);
    if(debug)
      System.out.println( "Exit  LayoutSwitchAction"  );
    return null;
    }

    /**
     * Retrieve key associated to user.
     * This key denote a definition in catalog.
     * Return user selected key, or "default" if none is set.
     */
  public static String getUserSetting( ComponentContext context, HttpServletRequest request )
  {
  HttpSession session = request.getSession( false );
  if( session == null )
    return null;

    // Retrieve attribute name used to store settings.
  String userSettingsName = (String)context.getAttribute( USER_SETTINGS_NAME_ATTRIBUTE );
  if( userSettingsName == null )
    userSettingsName = DEFAULT_USER_SETTINGS_NAME;

  return (String)session.getAttribute(userSettingsName);
  }

    /**
     * Set user setting value.
     * This key denote a definition in catalog.
     * Return user selected key, or "default" if none is set.
     */
  public static void setUserSetting( ComponentContext context, HttpServletRequest request, String setting )
  {
  HttpSession session = request.getSession();

    // Retrieve attribute name used to store settings.
  String userSettingsName = (String)context.getAttribute( USER_SETTINGS_NAME_ATTRIBUTE );
  if( userSettingsName == null )
    userSettingsName = DEFAULT_USER_SETTINGS_NAME;

  session.setAttribute(userSettingsName, setting);
  }

    /**
     * Get currently selected skin definition.
     */
  public static ComponentDefinition getCurrentDefinition( ComponentContext context, HttpServletRequest request, ServletContext servletContext )
    throws ServletException
  {
    // Get selected key
  String selected = getUserSetting(context, request);

  DefinitionCatalog catalog = getCatalog( context, request, servletContext);
  ComponentDefinition definition =  (ComponentDefinition)catalog.get( selected );
  if( definition == null )
    definition = (ComponentDefinition)catalog.getDefault();

  return definition;
  }

    /**
     * Get catalog of available skins.
     */
  public static DefinitionCatalog getCatalog( ComponentContext context, HttpServletRequest request, ServletContext servletContext )
    throws ServletException
  {
    // Retrieve name used to store catalog in application context.
    // If not found, use default name
  String catalogName = (String)context.getAttribute( CATALOG_NAME_ATTRIBUTE );
  if(catalogName == null)
    catalogName = DEFAULT_CATALOG_NAME;

  if(debug)
    System.out.println( "Catalog name=" + catalogName );
  try
    {
    DefinitionCatalog catalog = (DefinitionCatalog)servletContext.getAttribute( catalogName );
    if(catalog == null)
      { // create catalog
      if(debug)
        System.out.println( "Create catalog" );
      String catalogSettings = (String)context.getAttribute( CATALOG_SETTING_ATTRIBUTE );
      if(catalogSettings == null)
        throw new ServletException( "Error - CustomSkinAction : attribute '"
                                  + CATALOG_SETTING_ATTRIBUTE
                                  + "' not found in Tile's attributes. Need it to initialize catalog"  );
      catalog = new DefinitionCatalog( catalogSettings, request, servletContext );
      if(debug)
        System.out.println( "Catalog created" );
      servletContext.setAttribute( catalogName, catalog );
      } // end if
    return catalog;
    }
   catch(DefinitionsFactoryException ex )
    {
    if(debug)
        System.out.println( "Exception : " + ex.getMessage() );
    throw new ServletException( ex.getMessage() );
    }
  }
}