# 具体遇到的问题
UserServlet中怎么获取登录用户名？

# 报错信息的截图

# 相关课程内容截图

# 尝试过的解决思路和结果

# 粘贴全部相关代码，切记添加代码注释（请勿截图）

package com.imooc.web.action;

import java.io.IOException;

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 com.imooc.domain.User;

import com.imooc.service.UserService;

import com.imooc.service.impl.UserServiceImpl;

@WebServlet("/LoginServlet")

public class LoginServlet extends HttpServlet {

private static final long serialVersionUID = 1L;

  

    public LoginServlet() {

        super();

       

    }

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

//接收参数

String methodName=request.getParameter("method");

//判断

if("login".equals(methodName)) {

login(request,response);

}else if("logout".equals(methodName)) {

logout(request,response);

}

}

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

//1、销毁session

request.getSession().invalidate();

//2、跳转到登录页面

response.sendRedirect(request.getContextPath()+"/login.jsp");

}

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

// 完成验证码的校验:

// 获得session中保存的验证码的信息

String code1 = (String) request.getSession()

.getAttribute(com.google.code.kaptcha.Constants.KAPTCHA_SESSION_KEY);

// 接收前台表单提交的验证码的信息

String code2 = request.getParameter("checkCode");

if (code2 == null || !code2.equalsIgnoreCase(code1)) {

request.setAttribute("msg", "验证码输入不正确!");

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

return;

}

//接收页面提交过来的用户名和密码

String username=request.getParameter("username");

String password=request.getParameter("password");

//输出接收到的用户名和密码

System.out.println(username+"   "+password);

//数据封装

User user=new User();

user.setUsername(username);

user.setPassword(password);

//处理数据

UserService userService=new UserServiceImpl();

User existUser=userService.login(user);

//根据处理结果，完成页面跳转

if(existUser==null) {

//登录失败，返回到登录页面

request.setAttribute("msg", "用户名或密码错误");

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

}else {

//登录成功,保存用户信息

request.getSession().setAttribute("existUser", existUser);

response.sendRedirect(request.getContextPath()+"/MessageServlet");

// response.sendRedirect(request.getContextPath()+"/message_list.jsp");

}

}

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

doGet(request, response);

}

}

package com.imooc.web.action;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

@WebServlet("/UserServlet")

public class UserServlet extends HttpServlet {

private static final long serialVersionUID = 1L;

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

String methodName=request.getParameter("method");

if("edit".equals(methodName)) {

//根据已登录用户信息，将用户全部信息传递到edit_user.jsp页面

edit(request,response);

}

}

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

doGet(request, response);

}

/**

* 根据用户登录的信息，将所有用户信息查询出来并跳转至edit_jsp页面

* @param request

* @param response

*/

private void edit(HttpServletRequest request, HttpServletResponse response) {

//从登录用户中获取用户名

String userName=(String) request.getSession().getAttribute("existUser.getUsername");

System.out.println(userName);

}

}

​在这里输入代码，可通过选择【代码语言】突出显示