Session的应用——三天免登录

本是古典何须时尚 2023-08-17 16:10 129阅读 0赞

1、使用Cookie实现的登录的不足：

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            Connection con=null;
            login log= null;
          String account=request.getParameter("username");//获得表单数据只在此Servlet起作用 String password=request.getParameter("password");
            Cookie cookie=new Cookie(account,password);
            cookie.setPath("/Servlet_login_war_exploded/cookie");
            cookie.setMaxAge(3*24*3600);
            response.addCookie(cookie);
            try {
                con=C3p0Utils.getConnection();
                QueryRunner qr = new QueryRunner();
                String sql = "Select * from login where account=? and password=?";
                Object[] select = {account,password};
                log = qr.query(con, sql, new BeanHandler<login>((login.class)), select);
                if(log!=null){
    
                    response.getWriter().write("nihao"+account);
                }
                else{
    
                    response.getWriter().write("wrong");
                }
    
            }
            catch (SQLException e) {
                throw new RuntimeException(e);
            }
        }

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            response.setContentType("text/html; charset=utf-8");//设置浏览器编码格式
            response.getWriter().write("<html>");
            response.getWriter().write("<head>");
            response.getWriter().write("<title>");
            response.getWriter().write("Login");
            response.getWriter().write("</title>");
            response.getWriter().write("</head>");
            response.getWriter().write("<body bgcolor=\"aqua\">");
            response.getWriter().write("<center>");
            response.getWriter().write("<h3>");
       response.getWriter().write("欢迎你"+request.getParameter("account"));
            response.getWriter().write("</h3>");
            response.getWriter().write("</center>");
            response.getWriter().write("</body>");
        }

使用Cookie虽然实现了三天免登陆的基础功能，但是，如果在用Cookie登录成功后需要重定向到另外一个Cookie时，request获取的值在重定向的Servlet中已经不再起作用了。访问的结果只能是空值。

![1392562-20190920210007160-749070875.png][]

2、使用Session的请求共享功能，实现在不同的Servlet跳转过程中依旧能够通过request获得用户信息。

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            request.setCharacterEncoding("utf-8");
            response.setContentType("text/html; charset=utf-8");//设置浏览器编码格式
            Cookie[] cookies=request.getCookies();
            Connection con=null;
            login log= null;
            int successNum=0;
            try {
                con= C3p0Utils.getConnection();
                QueryRunner qr = new QueryRunner();
                String sql = "Select * from login";
                List<login> list = qr.query(con, sql, new BeanListHandler<login>((login.class)));
                if(cookies!=null) {
        //验证数据库中是否有与Cookie对应的用户
                    for (int i = 0; i < list.size(); i++) {
                        log= list.get(i);
                    for (Cookie cookie : cookies) {
                            if((log.getAccount().equals(cookie.getName()))&&(log.getPassword().equals(cookie.getValue()))){ HttpSession httpSession=request.getSession(); httpSession.setAttribute("login",log); successNum++; }
                    }
                    }
                    if(successNum>=1){
    
                        response.sendRedirect("/Servlet_login_war_exploded/main");//重定向
                    }
                    else{
                        request.getRequestDispatcher("page").forward(request,response);
                    }
    
                }
                else{
                    request.getRequestDispatcher("page").forward(request,response);//请求转发
                }
            }
            catch (SQLException e) {
                throw new RuntimeException(e);
            }
        }

在通过Cookie登录成功后，创建了Session，对Session进行了赋值，而在重定向到MainServlet后，可以冲Session中获取值。虽然在不同的Servlet中，是不同的请求，但是依旧能够通过Session获取值。

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        login log= (login) request.getSession().getAttribute("login");
            response.setContentType("text/html; charset=utf-8");//设置浏览器编码格式
            response.getWriter().write("<html>");
            response.getWriter().write("<head>");
            response.getWriter().write("<title>");
            response.getWriter().write("Login");
            response.getWriter().write("</title>");
            response.getWriter().write("</head>");
            response.getWriter().write("<body bgcolor=\"aqua\">");
            response.getWriter().write("<center>");
            response.getWriter().write("<h3>");
           response.getWriter().write("欢迎你"+log.getAccount());
            response.getWriter().write("</h3>");
            response.getWriter().write("</center>");
            response.getWriter().write("</body>");
        }

![1392562-20190920214140394-390986435.png][]

转载于:https://www.cnblogs.com/zhai1997/p/11559989.html

[1392562-20190920210007160-749070875.png]: /images/20230810/dc9a8184824641c6bec4aa9d4dfe6c57.png
[1392562-20190920214140394-390986435.png]: /images/20230810/c69ace6084894e3abafc742797e8ccaa.png