jsp向servlet提交数据报错

jsp向servlet提交数据报错如上图，我的程序如下，我觉得并没有限制doPost的使用啊，为什么会出现这个错误呢？
public class userServlet extends HttpServlet {
PreparedStatement st=null;
ResultSet rs=null;
Connection conn=null;

private static final String sql_in = null;
private static final long serialVersionUID = 1L;
   public void destroy() {}
   protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    this.doPost(request, response);
}

public void doPost(HttpServletRequest request, HttpServletResponse response, HttpSession session) throws ServletException, IOExcepton {

你的doPost(HttpServletRequest request, HttpServletResponse response, HttpSession session) 有3个参数， this.doPost(request, response);却只有两个参数

你看看doPost方法是否在servlet中.

当然在，图中最下面那个不就是吗