Session和Cookie综合案例

案例：验证码,rememberMe

1. 案例需求：
    1. 访问带有验证码的登录页面login.jsp
    2. 用户输入用户名，密码以及验证码。
        * 如果用户名和密码输入有误，跳转登录页面，提示:用户名或密码错误
        * 如果验证码输入有误，跳转登录页面，提示：验证码错误
        * 如果全部输入正确，则跳转到主页success.jsp，显示：用户名,欢迎您


2. 分析：其中有几个点需要注意,是要使用session的
    1. 验证码生成之后的获取,是存放在session中的
    2. 登录成功之后,user对象是存放在session中的,为了在success中获取用户信息
    3. 在写回信息(错误信息)也是放在session中的,也可以放在request中,但是在登陆成功之后的返回并不友好(是返回servlet不是jsp页面)
    4. 其中记住我使用的是cookie(通过用户选择下拉菜单栏来设置记住的时长或不记住)

3. 代码实现(省略了数据库,实体类,userdao工具类)
    * UserDao类
    public class UserDao {
        //获取jdbctemplate对象
        private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource());

        //select方法
        public User login(User loginUser){
            try {
                String sql = "select * from user where username = ? and password = ?";
                User user = template.queryForObject(sql, new BeanPropertyRowMapper<>(User.class),
                        loginUser.getUsername(),loginUser.getPassword());
                return user;
            } catch (DataAccessException e) {
                return null;
            }
        }

    }

    * loginServlet
    package com.qin.servlet;

    import com.qin.dao.UserDao;
    import com.qin.domain.User;

    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.*;
    import java.io.IOException;

    @WebServlet("/loginServlet")
    public class LoginServlet extends HttpServlet {
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            //设置页面的编码
            request.setCharacterEncoding("utf-8");
            //获取session
            HttpSession session = request.getSession();
            //如果页面刷新之后请求要删除之前存储的的错误信息session
            session.removeAttribute("loginerror");
            session.removeAttribute("checkerror");

            //获取系统生成验证码
            String checkCode = (String) session.getAttribute("checkCode");
            //让验证码获取之后失效
            session.removeAttribute("checkCode");
            //获取参数,封转对象
            String username = request.getParameter("username");
            String password = request.getParameter("password");
            User user = new User(username, password);

            //获取用户填写的验证码
            String checkcode = request.getParameter("checkcode");
            //忽略大小写比较checkcode
            if (checkCode != null && checkCode.equalsIgnoreCase(checkcode)) {

                //判断用户名密码是否输入正确
                UserDao dao = new UserDao();
                User login = dao.login(user);
                if (login != null) {
                    //登录成功,跳转success.jsp

                    //登录成功时候判断记住密码
                    rememberMe(request, response, username, password);

                    //设置user的session
                    request.getSession().setAttribute("user", login);
                    response.sendRedirect("/day16/success.jsp");

                } else {
                    //写回信息(使用request域对象,不建议,因为在登陆之后返回是返回的servlet)
                    //request.setAttribute("loginerror", "用户名或密码错误");
                    //request.getRequestDispatcher("/login.jsp").forward(request, response);

                    //使用session域对象
                    session.setAttribute("loginerror","用户名或密码错误");
                    response.sendRedirect("/day16/login.jsp");
                }
            } else {
                //写回信息(使用request域对象,不建议)
                //request.setAttribute("checkerror", "验证码错误");
                //request.getRequestDispatcher("/login.jsp").forward(request, response);

                //使用session域对象
                session.setAttribute("checkerror","验证码错误");
                response.sendRedirect("/day16/login.jsp");
            }


        }
        //抽取方法是否记住我
        private void rememberMe(HttpServletRequest request, HttpServletResponse response, String username, String password) {
            //获取是否记住密码的参数
            String remember = request.getParameter("remember");
            //使用cookie
            if (remember != null) {
                Cookie cookie = new Cookie("remName", username);
                Cookie cookie1 = new Cookie("remPass", password);
                int time = 0;
                if ("0".equals(remember)){
                    //不记住
                    time = 0;
                }
                if ("1".equals(remember)){
                    //一天
                    time = 60*60*24;
                }
                if ("2".equals(remember)){
                    //一周
                    time = 60*60*24*7;

                }
                if ("3".equals(remember)){
                    //一个月
                    time = 60*60*24*30;
                }
                //设置cookie的存活时间
                cookie.setMaxAge(time);
                cookie1.setMaxAge(time);
                //response返回cookie
                response.addCookie(cookie);
                response.addCookie(cookie1);
            }
        }

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

    *login.jsp
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>login小案例</title>
        <script>
            window.onload = function () {
                document.getElementById("check").onclick = function () {
                    this.src = "/day16/checkServlet?time=" + new Date().getTime();
                }
            }
        </script>
        <style>
            div {
                color: red;
            }
        </style>
    </head>
    <body>
    <%--拿到cookie--%>
    <% Cookie[] cookies = request.getCookies();
        String username = null;
        String password = null;
        if (cookies != null && cookies.length > 0) {
            for (Cookie cookie : cookies) {
                String name = cookie.getName();
                if ("remName".equals(name)){
                    username = cookie.getValue();
                }
                if ("remPass".equals(name)){
                    password =  cookie.getValue();
                }
            }

        }


    %>
    <form action="/day16/loginServlet" method="post">
        <table>
            <tr>
                <td>用户名</td>
                <td><input type="text" name="username" value="<%= username==null?"":username%>"></td>
            </tr>
            <tr>
                <td>密码</td>
                <td><input type="password" name="password" value="<%= password==null?"":password%>"></td>
            </tr>
            <tr>
                <td>验证码</td>
                <td><input type="text" name="checkcode"></td>
            </tr>
            <tr>
                <td colspan="2"><img id="check" src="/day16/checkServlet"></td>
            </tr>
            <tr>
                <td>记住密码</td>
                <td>
                    <select name="remember" id="rem">
                        <option value="0" selected>--不记住--</option>
                        <option value="1">--记住一天--</option>
                        <option value="2">--记住一周--</option>
                        <option value="3">--记住一月--</option>
                    </select>
                </td>
            </tr>
            <tr>
                <td colspan="2"><input type="submit" value="登录"></td>
            </tr>
        </table>

        <div>
            <%= request.getSession().getAttribute("checkerror") == null ? "" : request.getSession().getAttribute("checkerror")%>
        </div>
        <div>
            <%= request.getSession().getAttribute("loginerror") == null ? "" : request.getSession().getAttribute("loginerror")%>
        </div>
    </form>
    </body>
    </html>

    *验证码是一个工具类(借助了java.awt.*画出来的)
    package com.qin.servlet;

    import javax.imageio.ImageIO;
    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.awt.*;
    import java.awt.image.BufferedImage;
    import java.io.IOException;
    import java.util.Random;

    @WebServlet("/checkServlet")
    public class CheckServlet extends HttpServlet {
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            //验证码的完成
            //生成验证码
            int width = 150;
            int height = 35;
            //创建img对象
            BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
            //画笔对象
            Graphics p = image.getGraphics();
            //设置画笔颜色
            p.setColor(Color.pink);
            p.fillRect(0,0,width,height);

            //画边框
            p.setColor(Color.BLUE);
            p.drawRect(0,0,width-1,height-1);
            //生产验证码并记录
            StringBuilder stringBuilder = new StringBuilder();
            //生成随机角标
            String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
            Random random = new Random();
            for (int i = 1; i <= 4; i++) {
                p.setFont(new Font("微软雅黑",Font.BOLD,16));
                char ch = str.charAt(random.nextInt(str.length()));
                stringBuilder.append(ch);
                p.drawString(ch+"",width/5*i-4,height/2+1);
            }
            String checkCode = stringBuilder.toString();


            //存入一个session
            request.getSession().setAttribute("checkCode",checkCode);

            //画干扰线
            p.setColor(Color.green);
            for (int i = 0; i < 6; i++) {
                //生成随机的四条线
                int x1 = random.nextInt(width);
                int x2 = random.nextInt(width);
                int y1 = random.nextInt(height);
                int y2 = random.nextInt(height);

                p.drawLine(x1,y1,x2,y2);
            }
            //将图片对象输出到页面
            //图片对象,后缀名,输出流
            ImageIO.write(image,"jpg",response.getOutputStream());
        }

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

    * success.jsp
    <%@ page import="com.qin.domain.User" %><%--
      Created by IntelliJ IDEA.
      User: Sun
      Date: 2018/9/17
      Time: 19:47
      To change this template use File | Settings | File Templates.
    --%>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>登录成功</title>
    </head>
    <body>


        <h1>欢迎您,<%= ((User)request.getSession().getAttribute("user")).getUsername()%></h1>
    </body>
    </html>