简易案例：后台生成验证码

最新推荐文章于 2024-05-14 08:49:32 发布

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最新推荐文章于 2024-05-14 08:49:32 发布

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本文链接：https://blog.youkuaiyun.com/cx9977/article/details/109182603

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简易案例：后台生成验证码

作用

1. 防止恶意注册
2. 避免重复提交

代码

前端代码

<%--
  Created by IntelliJ IDEA.
  User: yllch
  Date: 2020/10/20
  Time: 10:15
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>用户注册页面</title>
</head>
<body>

<form action="" method="get">
    <center>
        用户名：<input type="text" name="username" placeholder="请输入用户名">
        <br> <br>
        密  &nbsp;码：<input type="password"  name="password" placeholder="请输入密码">
        <br> <br>
        验证码：<input type="text" name="yan" placeholder="请输入验证码">
    </center>
    <br>
    <center><img id="san" src="http://localhost:8080/ReqiestResponse_war_exploded/yan" alt="" height="50px" width="180px">
       <button onclick="change()">刷新</button>
    </center>

    <br>

    <center><input type="submit" value="提交"></center>
</form>
</body>
</html>
<script>
    function change() {
        document.getElementById("san").src("http://localhost:8080/ReqiestResponse_war_exploded/yan" + new Date().getTime());
    }
</script>

后端代码

@WebServlet(name = "ServletYan", value = "/yan")
public class ServletYan extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        int width=200;
        int height=100;
        //生成验证码 用代码来生成图片
        BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_BGR);
        //美化图片
        Graphics graphics = bufferedImage.getGraphics();
        graphics.setColor(Color.PINK);
        //填充背景
        graphics.fillRect(0,0,width,height);
        //设置边框
        graphics.setColor(Color.LIGHT_GRAY);
        graphics.drawRect(0,0,width-1,height - 1);
        //生成随机验证码
        graphics.setFont(new Font("楷体",Font.PLAIN,44));
        graphics.setColor(Color.gray);
        Random random = new Random();
        String s="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
        for (int i = 1; i <= 4; i++) {
            int nextInt = random.nextInt(s.length());
            char c = s.charAt(nextInt);
            graphics.drawString(String.valueOf(c),width/5*i,height / 5*3);

        }
        //画干扰线
        graphics.setColor(Color.BLACK);
        for (int i = 0; i < 10; i++) {
            int w = random.nextInt(width);
            int h = random.nextInt(height);
            int w1= random.nextInt(width);
            int h1 = random.nextInt(height);
            graphics.drawLine(w,h,w1,h1);

        }
        //响应
        ImageIO.write(bufferedImage,"png",response.getOutputStream());
    }

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

运行结果

好看一点的验证码

主体代码

@WebServlet(name = "ServletZheng", value = "/yan1")
public class ServletZheng extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        int width = 200;
        int height = 69;
        BufferedImage verifyImg = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        //生成对应宽高的初始图片
        String randomText = VerifyCode.drawRandomText(width, height, verifyImg);
        //单独的一个类方法，出于代码复用考虑，进行了封装。
        //功能是生成验证码字符并加上噪点，干扰线，返回值为验证码字符
        request.getSession().setAttribute("verifyCode", randomText);
        response.setContentType("image/png");//必须设置响应内容类型为图片，否则前台不识别
        OutputStream os = response.getOutputStream(); //获取文件输出流
        ImageIO.write(verifyImg, "png", os);//输出图片流
        os.flush();
        os.close();//关闭流
    }

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

工具类代码

package SanWa.YanZheng;

import java.awt.*;
import java.awt.image.BufferedImage;
import java.util.Random;

public class VerifyCode {

    public static String drawRandomText(int width, int height, BufferedImage verifyImg) {

        Graphics2D graphics = (Graphics2D) verifyImg.getGraphics();

        graphics.setColor(Color.gray);//设置画笔颜色-验证码背景色

        graphics.fillRect(0, 0, width, height);//填充背景

        graphics.setFont(new Font("微软雅黑", Font.BOLD, 40));

        //数字和字母的组合

        String baseNumLetter = "123456789abcdefghijklmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ";

        StringBuffer sBuffer = new StringBuffer();

        int x = 10;  //旋转原点的 x 坐标

        String ch = "";

        Random random = new Random();

        for (int i = 0; i < 4; i++) {

            graphics.setColor(getRandomColor());

            //设置字体旋转角度

            int degree = random.nextInt() % 30;  //角度小于30度

            int dot = random.nextInt(baseNumLetter.length());

            ch = baseNumLetter.charAt(dot) + "";

            sBuffer.append(ch);

            //正向旋转

            graphics.rotate(degree * Math.PI / 180, x, 45);

            graphics.drawString(ch, x, 45);

            //反向旋转

            graphics.rotate(-degree * Math.PI / 180, x, 45);

            x += 48;

        }

        //画干扰线

        for (int i = 0; i < 6; i++) {

            // 设置随机颜色

            graphics.setColor(getRandomColor());

            // 随机画线

            graphics.drawLine(random.nextInt(width), random.nextInt(height),

                    random.nextInt(width), random.nextInt(height));

        }

        //添加噪点

        for (int i = 0; i < 30; i++) {

            int x1 = random.nextInt(width);

            int y1 = random.nextInt(height);

            graphics.setColor(getRandomColor());

            graphics.fillRect(x1, y1, 2, 2);

        }
        return sBuffer.toString();
    }

    /**
     * 随机取色
     */

    private static Color getRandomColor() {
        Random ran = new Random();
        Color color = new Color(ran.nextInt(256),
                ran.nextInt(256), ran.nextInt(256));
        return color;
    }
}

运行结果