Session案例一次性验证码登录

来源：互联网发布：mac qq接收文件编辑：程序博客网时间：2024/04/30 02:16

验证码的实现原理：
在一个Servlet中生成验证，并把验证码上的数据保存在Session，用户提交验证码之后，会提交给另外一个Servlet程序。在获取用户提交数据的Servlet中的从Session中把验证码取出，在取出的同时从Session中把验证码删除。

1.注册页面：register.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>    <base href="<%=basePath%>">    <title>My JSP 'login.jsp' starting page</title>    <meta http-equiv="pragma" content="no-cache">    <meta http-equiv="cache-control" content="no-cache">    <meta http-equiv="expires" content="0">        <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">    <meta http-equiv="description" content="This is my page">    <!--    <link rel="stylesheet" type="text/css" href="styles.css">    -->    <script type="text/javascript">        function _changImg(){            document.getElementById("myimg").src = "/day11/checkImg?" + new Date().getMilliseconds();        }    </script>  </head>  <body>    <center>        <form action="/day11/regist" method="post">            <table>                <tr>                    <td>用户名<font color="red">*</font></td>                    <td><input type="text" name="name"/></td>                </tr>                           <tr>                    <td>密码</td>                    <td><input type="password" name="password"/></td>                </tr>                                                   <tr>                    <td>输入验证码</td>                    <td>                        <input type="text" name="form_checkcode" />                        <img style="cursor: pointer;" alt="" src="/day11/checkImg" id="myimg" onclick="_changImg();"/>                        <a href="javascript:void(0);" onclick="_changImg();">看不清，换一张</a>                        <font color="red">${imgError }</font>                    </td>                </tr>                               <tr>                    <td><input type="submit" value="注册" /></td>                </tr>            </table>                </form>    </center>  </body></html>

2.生成验证码参考：cn.itcast.session.CheckImgServlet

public class CheckImgServlet extends HttpServlet {    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        int width = 120;        int height = 40;        // 先生成一张纸        BufferedImage bufi = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);        // 画笔        Graphics g = bufi.getGraphics();        // 设置背景颜色        // 修改画笔颜色        g.setColor(Color.white);        // 填充        g.fillRect(0, 0, width, height);        // 绘制边框        // 设置边框颜色        g.setColor(Color.red);        // 画边框        g.drawRect(0, 0, width - 1, height - 1);        // 准备一些数据        String data = "ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890abcdefghijklmnopqrstuvwxyz";        // 生成随机对象        Random r = new Random();        String checkcode = "";        // 生成4个随机的数字        for (int i = 0; i < 4; i++) {            // 生成随机颜色            g.setColor(new Color(r.nextInt(255), r.nextInt(255), r.nextInt(255)));            // 设置字体            g.setFont(new Font("宋体", Font.ITALIC, 25));            String c = data.charAt(r.nextInt(data.length())) + "";            g.drawString(c, 10 + (20 * i), 30);            checkcode += c;        }        // 将生成的验证码放到 session中        request.getSession().setAttribute("session_checkcode", checkcode);        // 画干扰线        for (int i = 0; i < 8; i++) {            // 设置随机颜色            g.setColor(new Color(r.nextInt(255), r.nextInt(255), r.nextInt(255)));            // 画线 两点确定一线            g.drawLine(r.nextInt(width), r.nextInt(height), r.nextInt(width), r.nextInt(height));        }        // 将图片输出到浏览器        ImageIO.write(bufi, "jpg", response.getOutputStream());    }    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {    }}

3.验证码的验证参考：cn.itcast.session.RegistServlet

public class RegistServlet extends HttpServlet {    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {    }    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        // 校验验证码的有效性: 服务端生成的验证码 和 表单提交的验证码一致才算有效        // 服务端生成的验证码 保存在 session容器中        // 获得session中的验证码        HttpSession session = request.getSession();        String session_checkcode = (String) session.getAttribute("session_checkcode");        // 使用完后，迅速清除session中验证码的属性        session.removeAttribute("session_checkcode");        // 获得表单提交的验证码        String form_checkcode = request.getParameter("form_checkcode");        // 判断什么是非法 如果非法，终止        if (session_checkcode == null || !session_checkcode.equals(form_checkcode)) {            // 说明验证码错误            request.setAttribute("imgError", "验证码错误！");            // 将request对象转发给 login.jsp            request.getRequestDispatcher("/login.jsp").forward(request, response);            // 结束当前方法            return;        }        // 如果合法， 继续校验用户名和密码的有效        String username = request.getParameter("username");        String password = request.getParameter("password");    }}

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