Example 7.14 Servlet Front Strategy Sample Code

public class EmployeeController extends HttpServlet {
  // Initializes the servlet.
  public void init(ServletConfig config) throws 
    ServletException {
    super.init(config);
  }

  // Destroys the servlet.
  public void destroy() {
  }

  /** Processes requests for both HTTP  
   * <code>GET</code> and <code>POST</code> methods.
   * @param request servlet request
   * @param response servlet response
   */
  protected void processRequest(HttpServletRequest 
    request, HttpServletResponse response)
    throws ServletException, java.io.IOException {
    String page;

    /**ApplicationResources provides a simple API 
     * for retrieving constants and other 
     * preconfigured values**/
    ApplicationResources resource = 
      ApplicationResources.getInstance();
    try {

      // Use a helper object to gather parameter 
      // specific information.
      RequestHelper helper = new
         RequestHelper(request);

      Command cmdHelper= helper.getCommand();

      // Command helper perform custom operation
      page = cmdHelper.execute(request, response);

    }
    catch (Exception e) {
      LogManager.logMessage(
        "EmployeeController:exception : " + 
        e.getMessage());
      request.setAttribute(resource.getMessageAttr(), 	
        "Exception occurred : " + e.getMessage());
      page = resource.getErrorPage(e);
    }
    // dispatch control to view
    dispatch(request, response, page);
  }

  /** Handles the HTTP <code>GET</code> method.
   * @param request servlet request
   * @param response servlet response
   */
  protected void doGet(HttpServletRequest request, 
    HttpServletResponse response)
    throws ServletException, java.io.IOException {
      processRequest(request, response);
  }

  /** Handles the HTTP <code>POST</code> method.
   * @param request servlet request
   * @param response servlet response
   */
  protected void doPost(HttpServletRequest request, 
    HttpServletResponse response)
    throws ServletException, java.io.IOException {
        processRequest(request, response);
  }

  /** Returns a short description of the servlet */
  public String getServletInfo() {
    return "Front Controller Pattern" + 
      " Servlet Front Strategy Example";
  }

  protected void dispatch(HttpServletRequest request, 
    HttpServletResponse response,
    String page) 
  throws  javax.servlet.ServletException, 
    java.io.IOException {
    RequestDispatcher dispatcher = 
      getServletContext().getRequestDispatcher(page);
    dispatcher.forward(request, response);
  }
}