请问老师,如何在登陆失败时将msg中的信息输出在页面上?

package com.imooc.servlet;

import com.google.code.kaptcha.Constants;
import com.imooc.service.CourseServiceImpl;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class LoginServlet extends HttpServlet {
   protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       this.doGet(request, response);
   }

   protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       String username = request.getParameter("username");
       String password = request.getParameter("password");

       String checkCode = request.getParameter("checkCode");
       String sessionKey = (String) request.getSession().getAttribute(Constants.KAPTCHA_SESSION_KEY);

       int i = CourseServiceImpl.getCd().login(username, password);
       if (i == 1 && checkCode.equalsIgnoreCase(sessionKey)) {
           System.out.println("登陆成功");
           request.getSession().setAttribute("username", username);
           if (username.equals("imooc")) {
               request.getSession().setAttribute("flag", 1);
           } else {
               request.getSession().setAttribute("flag", 0);
           }
           request.getRequestDispatcher("/jsp/server.jsp").forward(request, response);
       } else {
           System.out.println("登陆失败");
           request.setAttribute("msg", "用户名或密码错误");
           request.getRequestDispatcher("/jsp/index.jsp").forward(request, response);
       }

   }
}