String servletPath = request.getServletPath();

         String methodName = servletPath.substring(1);

         methodName = methodName.substring(0, methodName.length() - 3);

         Method method;

         try {

             method = getClass().getDeclaredMethod(methodName,

                     HttpServletRequest.class, HttpServletResponse.class);

             method.invoke(this, request,response);

         } catch (NoSuchMethodException | SecurityException | IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {

             // TODO Auto-generated catch block

             e.printStackTrace();

         }

     }

     private void update(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

         System.out.println("update");

     }

     private void query(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

         List<User> list = dao.getAll();

         request.setAttribute("list", list);

         request.getRequestDispatcher("/index.jsp").forward(request, response);;

         System.out.println("query");

     }

     private void delete(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

         System.out.println("delete");

     }private void add(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

         System.out.println("add");

     }

  <servlet-mapping>

     <servlet-name>UserServlet</servlet-name>

     <url-pattern>*.do</url-pattern>

   </servlet-mapping>

<a href="add.do">add</a>

<a href="delete.do">delete</a>

<a href="query.do">query</a>

<a href="update.do">update</a>