code: public boolean handle(HttpServletRequest request, HttpServletResponse response)
              throws ServletException, IOException {
          if (defaultServletName != null) {
              RequestDispatcher rd = servletContext.getNamedDispatcher(defaultServletName);
              if (rd == null) {
                  throw new IllegalStateException("A RequestDispatcher could not be located for the default servlet '" +
                          defaultServletName + "'");
              }
              rd.forward(request, response);
              return true;
          } else {
              return false;
          }
      }
docs: Process the actual dispatching.
  
  @param request current HTTP servlet request
  @param response current HTTP servlet response
  @return true, if successful
  @throws ServletException the servlet exception
  @throws IOException if an input or output error occurs while the servlet is handling the HTTP request