解决Javaweb 提交表单到servlet时出现空白页面,但网站不报错问题

package cn.itcast.web.servlet; 
import cn.itcast.domain.User;
import cn.itcast.service.UserService;
import cn.itcast.service.impl.UserServiceImpl; 
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.Http.httpservlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
 
@WebServlet("/findUserServlet")
public class FindUserServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 
        // 1.获取id
        String id = request.getParameter("id");
        // 2.通过id查找User
        UserService service = new UserServiceImpl();
        User user = service.findUserById(id);
        // 3.存储
        request.setAttribute("user",user);
        // 4.转发
        request.getRequestDispatcher("/update.jsp").forward(request, response); 
    } 
 
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    }
}

this.doPost(request, response);