Session验证码案例Java

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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

在生成验证码的时候将它的值存入到 session 中，在比对的时候再取出来进行对比

index.jsp

<%--
  Created by IntelliJ IDEA.
  User: tanglei
  Date: 2020/6/26
  Time: 下午 12:48
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>login</title>


    <script>
        window.onload = function(){document.getElementById("img").onclick = function(){this.src="/login_time_war_exploded/checkCode?time="+new Date().getTime();}
        }


    </script>
    <style>
        div{color: red;}

    </style>
</head>
<body>

<form action="/login_time_war_exploded/login" method="post">
    <table>
        <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 id="img" src="/login_time_war_exploded/checkCode"></td>
        </tr>
        <tr>
            <td colspan="2"><input type="submit" value="登录"></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

<%--
  Created by IntelliJ IDEA.
  User: tanglei
  Date: 2020/6/26
  Time: 下午 6:27
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1><%=request.getSession().getAttribute("user")%>, 欢迎您 </h1>
</body>
</html>

验证码 checkCode.java

package cn.guizimo.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("/checkCode")
public class CheckCode extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        int width = 100;
        int height = 50;
        // 创建图片对象
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_BGR);

        // 美化
        Graphics g = image.getGraphics();
        // 背景
        g.setColor(Color.PINK);
        g.fillRect(0, 0, width, height);
        // 边框
        g.setColor(Color.BLUE);
        g.drawRect(0, 0, width - 1, height - 1);

        String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
        Random ran = new Random();
        StringBuilder sb = new StringBuilder();
        for (int i = 1; i <= 4; i++) {int index = ran.nextInt(str.length());
            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
        req.getSession().setAttribute("checkCode_session",checkCode_session);

        // 干扰线
        g.setColor(Color.GREEN);
        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);
        }


   // 输出图片到浏览器
        ImageIO.write(image, "jpg", resp.getOutputStream());

    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {this.doPost(req, resp);
    }
}

login.java

package cn.guizimo.servlet;

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 javax.servlet.http.HttpSession;
import java.io.IOException;

@WebServlet("/login")
public class Login extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1. 设置 request 编码
        req.setCharacterEncoding("utf-8");
        //2. 获取参数
        String username = req.getParameter("username");
        String password = req.getParameter("password");
        String checkCode = req.getParameter("checkCode");
        //3. 先获取生成的验证码
        HttpSession session = req.getSession();
        String checkCode_session = (String) session.getAttribute("checkCode_session");
        // 删除 session 中存储的验证码
        //session.removeAttribute("checkCode_session");
        //3. 先判断验证码是否正确
        if(checkCode_session!= null && checkCode_session.equalsIgnoreCase(checkCode)){
            // 忽略大小写比较
            // 验证码正确
            // 判断用户名和密码是否一致
            if("zhangsan".equals(username) && "123".equals(password)){// 需要调用 UserDao 查询数据库
                // 登录成功
                // 存储信息，用户信息
                session.setAttribute("user",username);
                // 重定向到 success.jsp
                resp.sendRedirect(req.getContextPath()+"/success.jsp");
            }else{
                // 登录失败
                // 存储提示信息到 request
                req.setAttribute("login_error","用户名或密码错误");
                // 转发到登录页面
                req.getRequestDispatcher("/login.jsp").forward(req,resp);
            }


        }else{
            // 验证码不一致
            // 存储提示信息到 request
            req.setAttribute("cc_error","验证码错误");
            // 转发到登录页面
            req.getRequestDispatcher("/login.jsp").forward(req,resp);

        }
    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {this.doPost(req, resp);
    }
}

Session验证码案例Java

Session– 验证码案例（Java）

案例

思路

代码

index.jsp

success.jsp

验证码 checkCode.java

login.java

测试

登录界面

验证码错误

用户名密码错误

登录成功