Yummy 22:31:37
package com.aojie.web.Servlet;

import com.aojie.domain.User;
import com.aojie.service.UserService;
import com.aojie.service.impl.UserServiceImpl;
import org.apache.commons.beanutils.BeanUtils;

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;
import java.lang.reflect.InvocationTargetException;
import java.util.Map;

/**
 * @author aojie
 * @fuction
 * @create 2020-04-28 19:53
 */
@WebServlet("/UpdateUserServlet")
public class UpdateUserServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //设置编码格式
        request.setCharacterEncoding("utf-8");
        //获取表单数据
        Map<String, String[]> parameterMap = request.getParameterMap();
        //封装对象
        User user = new User();
        try {
            BeanUtils.populate(user,parameterMap);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
        //调用service中update方法
        UserService service = new UserServiceImpl();
        service.updateUser(user);
        //重定向到UserlistServlet
        response.sendRedirect(request.getContextPath()+"/UserListServlet");
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }
}

Yummy 22:31:45
package com.aojie.web.Servlet;

import com.aojie.domain.User;
import com.aojie.service.UserService;
import com.aojie.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;

/**
 * @author aojie
 * @fuction
 * @create 2020-04-28 19:53
 */
@WebServlet("/FindUserServlet")
public class FindUserServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String id = request.getParameter("id");
        UserService service = new UserServiceImpl();
        User user = service.findUser(id);
        request.setAttribute("user",user);
        request.getRequestDispatcher("/update.jsp").forward(request,response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }
}