1.pom依赖

        <!-- 谷歌 Captcha验证码依赖 -->
        <dependency>
            <groupId>com.github.axet</groupId>
            <artifactId>kaptcha</artifactId>
            <version>0.0.9</version>
        </dependency>

2.新建CaptchaConfig.java文件

/**
 * 谷歌 Captcha验证码配置类
 */
@Configuration
public class CaptchaConfig {

    @Bean
    public DefaultKaptcha defaultKaptcha() {
        // 验证码生成器
        DefaultKaptcha defaultKaptcha = new DefaultKaptcha();
        // 配置
        Properties properties = new Properties();
        // 是否有边框
        properties.setProperty("kaptcha.border","yes");
        // 设置边框颜色
        properties.setProperty("kaptcha.border.color","105,179,90");
        // 验证码
        properties.setProperty("kaptcha.session.code","code");
        // 验证码文本字符颜色，默认为黑色
        properties.setProperty("kaptcha.textproducer.font.color","blue");
        // 设置字体样式
        properties.setProperty("kaptcha.textproducer.font.names","宋体,楷体,微软雅黑");
        // 字体大小，默认为40
        properties.setProperty("kaptcha.textproducer.font.size","30");
        // 字符长度，默认为5
        properties.setProperty("kaptcha.textproducer.char.length","4");
        // 字符间距，默认为2
        properties.setProperty("kaptcha.textproducer.char.space","4");
        // 验证码图片宽度，默认为200
        properties.setProperty("kaptcha.iamge.width","100");
        // 验证码图片高度，默认为40
        properties.setProperty("kaptcha.iamge.height", "40");
        Config config = new Config(properties);
        defaultKaptcha.setConfig(config);
        return defaultKaptcha;
    }
}

3.新建CaptchaController接口

/**
 * 谷歌 Captcha验证码 接口
 */
@RestController
public class CaptchaController {
    @Autowired
    private DefaultKaptcha defaultKaptcha;

    @ApiOperation(value = "验证码")
    @GetMapping(value = "/captcha",produces = "image/jpeg")
    public void captcha(HttpServletRequest request, HttpServletResponse response) {
        // 定义response输出类型为image/jpeg类型
        response.setDateHeader("Expires", 0);
        response.setHeader("Cache-Control", "no-store, no-cache, must-revalidate");
        response.addHeader("Cache-Control", "post-check=0, pre-check=0");
        response.setHeader("Pragma", "no-cache");
        response.setContentType("image/jpeg");

        // 开始生成验证码
        String text = defaultKaptcha.createText(); // 获取验证码文本内容
        System.out.println("验证码文本内容：" + text);
        request.getSession().setAttribute("captcha", text);
        BufferedImage image = defaultKaptcha.createImage(text); // 根据文本内容创建图形验证码
        ServletOutputStream outputStream = null;
        try {
            outputStream = response.getOutputStream();
            ImageIO.write(image, "jpg", outputStream); // 输出流输出图片，格式为jpg
            outputStream.flush();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (null != outputStream) {
                try {
                    outputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        // 生成验证码结束
    }
}