Source code: com/sample/tutorial/update/controller/servlet/UpdateTutorialServlet.java

   /*
    * UpdateTutorialServlet.java
    *
    * Copyright (c) 2001, 2002 Aendvari, Ltd. All Rights Reserved.
    *
    * See the file LICENSE for terms of use.
    *
    */
   
  package com.sample.tutorial.update.controller.servlet;
  
  import java.io.*;
  
  import javax.servlet.*;
  import javax.servlet.http.*;
  
  import com.aendvari.cerberus.component.assembly.*;
  import com.aendvari.cerberus.component.descriptor.*;
  import com.aendvari.cerberus.component.descriptor.parser.*;
  import com.aendvari.cerberus.component.directory.*;
  
  import com.aendvari.common.model.*;
  import com.aendvari.common.model.xalan.*;
  
  import com.aendvari.common.util.*;
  
  import com.aendvari.hermes.broker.*;
  import com.aendvari.hermes.broker.http.*;
  
  import com.aendvari.satyr.servlet.*;
  import com.aendvari.satyr.servlet.gateway.HttpFormGateway.ContextModifier;
  import com.aendvari.satyr.servlet.gateway.tethys.*;
  
  import com.aendvari.tethys.tag.*;
  
  import java.util.*;
  
  /**
   * Main servlet for the update tutorial.
   *
   * @author  Trevor Milne
   *
   */
  
  public class UpdateTutorialServlet extends HttpServlet
  {
    protected final String Broker = "tutorial-update/broker";
  
    /**
     * Process an HTTP "GET" request.
     *
     * @param    request            The servlet request being processed.
     * @param    response          The servlet response being created.
     *
     * @exception  IOException          Thrown if an input/output error occurs.
     * @exception  ServletException      Thrown if a servlet exception occurs.
     *
     */
  
    public void doGet(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException
    {
      ModelTree modelTree = null;
  
      // retrieve model tree from session, if any
      try
      {
        modelTree = ServletModelUtil.getModelTree(request.getSession());
      }
      catch (ServletModelUtil.NoModelException exception)
      {
        // create application view model
  
        // determine the location of the application model
        String path = getServletContext().getRealPath("model.xml");
  
        // create a model tree instance
        modelTree = new XalanModelTree();
  
        // load the model from the stream
        try
        {
          modelTree.loadFromFile(path);
        }
        catch (ModelParserException parseException)
        {
          throw new ServletException(parseException);
        }
  
        // place the model into the client's session
        ServletModelUtil.setModelTree(request.getSession(), modelTree);
      }
  
      // show the main screen
  
      // get the message broker
      MessageBroker broker = (MessageBroker)getServletConfig().getServletContext().getAttribute(Broker);
  
      // create a context for the connection
     HttpMessageBrokerContext brokerContext = new HttpMessageBrokerContext();
 
     brokerContext.setServletConfig(getServletConfig());
     brokerContext.setRequest(request);
     brokerContext.setResponse(response);
     brokerContext.setSession(request.getSession());
 
     // place model into broker context for components to use
     brokerContext.getProperties().setObject("model", modelTree);
 
     // create a connection
     MessageBrokerConnection connection = broker.createConnection();
 
     // set the context into the connection
     connection.setContext(brokerContext);
 
     // tell login view to display
     connection.publish(
       connection.getTopic("main.show"), connection.createMessage());
   }
 
   /**
    * Process an HTTP "POST" request.
    *
    * @param    request            The servlet request being processed.
    * @param    response          The servlet response being created.
    *
    * @exception  IOException          Thrown if an input/output error occurs.
    * @exception  ServletException      Thrown if a servlet exception occurs.
    *
    */
 
   public void doPost(HttpServletRequest request, HttpServletResponse response)
     throws ServletException, IOException
   {
     try
     {
       // retrieve the model from the session
       final ModelTree modelTree = ServletModelUtil.getModelTree(request.getSession());
 
       // retrieve the message broker from the servlet context
       MessageBroker broker = (MessageBroker)getServletConfig().getServletContext().getAttribute(Broker);
 
       // process the HTTP post
       MessageGateway.process(broker, getServletConfig(), request, response,
         null,
         // use an anonymous class to extend the gateway
         new ContextModifier() {
           public void modifyContext(
             MessageBrokerContext context,
             ServletConfig servletConfig,
             HttpServletRequest request, HttpServletResponse response)
               throws ServletException
           {
             // place model into broker context for components to use
             context.getProperties().setObject("model", modelTree);
           }
         },
         null);
     }
     // if no model tree, then there is no session, start the application
     catch (ServletModelUtil.NoModelException exception)
     {
       doGet(request, response);
     }
   }
 
   /**
    * Initialize the servlet.
    *
    * @exception  ServletException      Thrown if a servlet exception occurs.
    *
    */
 
   public void init()
     throws ServletException
   {
     // create the MessageBroker
     MessageBroker broker = new MessageBroker();
     getServletConfig().getServletContext().setAttribute(Broker, broker);
 
     // assemble components
     try
     {
       // retrieve component configuration
       String configuration = getServletConfig().getInitParameter("configuration");
 
       // get assembly descriptor stream
       InputStream input = ResourceLoader.getResourceAsStream(configuration);
 
       // parse the descriptor
       AssemblyParser parser = new AssemblyParser();
       AssemblyDescriptor descriptor = parser.parse(input);
 
       // create connection to broker
       MessageBrokerConnection connection = broker.createConnection();
 
       // create output objects
       AssemblyContext context = new AssemblyContext(broker);
       ComponentDirectory directory = new ComponentDirectory();
 
       // assemble components
       ComponentAssembler assembler = new ComponentAssembler(context, descriptor, directory);
       assembler.assemble();
     }
     catch (Exception exception)
     {
       exception.printStackTrace(System.err);
       throw new ServletException(exception);
     }
 
     System.out.println("UpdateTutorialServlet initialized");
   }
 }