一个servlet处理多个功能

servlet中：

 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");
     }

web.xml文件：

  <servlet-mapping>
     <servlet-name>UserServlet</servlet-name>
     <url-pattern>*.do</url-pattern>
   </servlet-mapping>

jsp：

<a href="add.do">add</a>
<a href="delete.do">delete</a>
<a href="query.do">query</a>
<a href="update.do">update</a>