Session-判断用户登陆验证码是否正确

验证码为随机生成，服务器从 session 获取验证码，并和用户输入的验证码进行比对，结果通过 requesrt 转发到 success.jsp 和 login.jsp

简单登陆页面：

<html>
<head>
    <title>登陆</title>
    <script>
        window.onload = function () {
            document.getElementById("img").onclick = function(){
                this.src="/day16/checkCodeServlet?time="+new Date().getTime();
            }
        }
    </script>
    <style>
        div{
            color:red;
        }
    </style>
</head>
<body>
        <form action="/day16/loginServlet" method="post">
            <table align="center">
                <tr>
                    <td>用户名</td>
                    <td><input type="text" name="username"></td>
                </tr>
                <tr>
                    <td>密码</td>
                    <td><input type="password" name="password"></td>
                </tr>
                <tr>
                    <td>验证码</td>
                    <td><input type="text" name="checkCode"></td>
                </tr>
                <tr>
                    <td colspan="2"><img src="/day16/checkCodeServlet" id="img"></td>
                </tr>
                <tr>
                    <td colspan="2"><input type="submit" value="登陆"></td>
                </tr>
            </table>
        </form>
        <div>
            <%=request.getAttribute("cc_error")==null? "":request.getAttribute("cc_error")%>
        </div>
        <div>
            <%=request.getAttribute("login_error")==null?"":request.getAttribute("login_error")%>
        </div>
</body>
</html>

success.jsp

登陆成功后跳转到该页面，并获取用户信息展示：

<html>
<head>
    <title>Title</title>
</head>
<body>
    <h1><%=request.getSession().getAttribute("user") %>,欢迎您</h1>
</body>
</html>

LoginServlet

获取 session 中验证码信息，进行比对，并转发结果到相关页面。

@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //设置request编码
        request.setCharacterEncoding("utf-8");
        //获取参数
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        String checkCode = request.getParameter("checkCode");
        //获取生成的验证码
        HttpSession session = request.getSession();
        String checkCode_session = (String) session.getAttribute("checkCode_session");
        //删除session中存储的验证码
        session.removeAttribute("checkCode_session");
        //判断验证码是否正确
        if(checkCode_session != null &&checkCode_session.equalsIgnoreCase(checkCode)){
            //忽略大小写比较字符串
            //验证码正确
            //判断用户名和密码是否一样
            if ("zhangsan".equals(username)&&"123".equals(password)){//查询数据库
                //登陆成功
                //存储用户信息
                session.setAttribute("user",username);
                //重定向到success.jsp
                response.sendRedirect(request.getContextPath()+"/success.jsp");
            }else {
                //登陆失败
                //存储提示信息到request
                request.setAttribute("login_error","用户名或密码错误");
                //转发到登陆页面
                request.getRequestDispatcher("/login.jsp").forward(request,response);
            }
        }else {
            //验证码不一致
            //存储提示信息到request
            request.setAttribute("cc_error","验证码错误");
            //转发到登陆页面
            request.getRequestDispatcher("/login.jsp").forward(request,response);
        }

    }

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

CheckCodeServlet

生成随机验证码，并存入 session 。

@WebServlet("/checkCodeServlet")
public class CheckCodeServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        int width = 100;
        int height = 50;
        //创建一个对象，在内存中画图（验证码图片对象）
        BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_3BYTE_BGR);
        //美化图片
        //填充背景色
        Graphics g = image.getGraphics();//画笔对象
        g.setColor(Color.pink);//设置画笔颜色
        g.fillRect(0,0,width,height);
        //画边框
        g.setColor(Color.BLUE);
        g.drawRect(0,0,width -1,height-1);

        String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
        //生成随机脚标
        Random ran = new Random();
        StringBuilder sb = new StringBuilder();
        //写验证码
        for (int i = 1; i <= 4; i++) {
            int index = ran.nextInt(str.length());
            //获取字符
            char ch = str.charAt(index);
            sb.append(ch);
            g.drawString(ch+"",width/5*i,height/2);
        }
        String checkCode_session = sb.toString();
        //将验证码存入session
        request.getSession().setAttribute("checkCode_session",checkCode_session);
        //画干扰线
        g.setColor(Color.green);
        //随机生成坐标点
        for (int i = 0; i < 10; i++) {
            int x1 = ran.nextInt(width);
            int x2 = ran.nextInt(width);

            int y1 = ran.nextInt(height);
            int y2 = ran.nextInt(height);
            g.drawLine(x1,y1,x2,y2);
        }

        //键土拍你输出到页面展示
        ImageIO.write(image,"jpg",response.getOutputStream());

    }

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

Session