SpringBoot实现Thymeleaf验证码生成

使用后台返回验证码图片，验证码存到session中后端实现校验，前端只展示验证码图片。

本篇用SpringBoot Thymeleaf实现验证码生成。

创建springboot项目 引入依赖

完整pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.6.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>web</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>web</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>

        <!-- ThymeLeaf 依赖 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

application.yml配置 Thymeleaf

#Thymeleaf配置
spring:
  mvc:
    static-path-pattern: /**
  thymeleaf:
    mode: HTML
    encoding: UTF-8
    #关闭缓存
    cache: false

创建CaptchaController.java 类

package com.example.web.controller;

import com.example.web.util.VerifyCode;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.imageio.ImageIO;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;

@RestController
public class CaptchaController {
    /* 获取验证码图片*/

    @RequestMapping("/getVerifyCode")
    public void getVerificationCode(HttpServletResponse response, HttpServletRequest request) {
        try {
            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
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

创建VerifyCode.java 工具类

package com.example.web.util;

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.WHITE);//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";

        StringBuilder builder = new StringBuilder();
        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) + "";
            builder.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 builder.toString();
    }

    /**
     * 随机取色
     */
    private static Color getRandomColor() {
        Random ran = new Random();
        return new Color(ran.nextInt(256),
                ran.nextInt(256), ran.nextInt(256));

    }
}

创建UserController.java 类

package com.example.web.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
public class UserController {
    @RequestMapping("/login")
    public String login() {
        return "login";
    }
}

resources/templates目录下创建login.html

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Show User</title>
</head>
<body>
<a href="javascript:void(0);" rel="external nofollow" title="点击更换验证码">
    <img th:src="@{getVerifyCode}" onclick="changeCode()" class="verifyCode"/>
</a>
</body>
<!-- 引入JQuery -->
<script src="../static/js/jquery.min.js" th:src="@{/js/jquery.min.js}"></script>
<script>
    function changeCode() {
        const src = "/getVerifyCode?" + new Date().getTime(); //加时间戳，防止浏览器利用缓存
        $('.verifyCode').attr("src", src);
    }
</script>
</html>

启动项目访问http://localhost:8080/login

点击图片可以更换验证码，至于后面的后台验证就不讲了。
参考文章后台java 实现验证码生成

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