具体实现

导入Kaptcha依赖

<dependency>  
    <groupId>com.github.penggle</groupId>  
    <artifactId>kaptcha</artifactId>  
    <version>2.3.2</version>  
</dependency>

配置Kaptcha

设置验证码的方式有两种，一个是设置图片类的，一个是设置文本类的，具体配置代码如下所示：

@Configuartion
public class KaptchaConfig {
	@Bean
	public DefaultKaptcha getDefaultKaptcha() {
		com.google.code.kaptcha.impl.DefaultKaptcha defaultKaptcha = new com.google.code.kaptcha.impl.DefaultKaptcha();
		Properties properties = new Properties();
		// 图片边框
		properties.setProperty("kaptcha.border", "yes");
		// 边框颜色
		properties.setProperty("kaptcha.border.color", "105,179,90");
		// 字体颜色
		properties.setProperty("kaptcha.textproducer.font.color", "red");
		// 图片宽
		properties.setProperty("kaptcha.image.width", "110");
		// 图片高
		properties.setProperty("kaptcha.image.height", "40");
		// 字体大小
		properties.setProperty("kaptcha.textproducer.font.size", "30");
		// session key
		properties.setProperty("kaptcha.session.key", "code");
		// 验证码长度
		properties.setProperty("kaptcha.textproducer.char.length", "4");
		// 字体
		properties.setProperty("kaptcha.textproducer.font.names", "宋体,楷体,微软雅黑");

		properties.setProperty("kaptcha.noise.color", "35,37,38");

		Config config = new Config(properties);
		defaultKaptcha.setConfig(config);

		return defaultKaptcha;
	}
}

控制层代码实现

@Api(tags = {"Google-kaptcha验证码"})
@RestController
@RequestMapping("/api/kaptcha")
public class KaptchaController {

    @Autowired
    DefaultKaptcha defaultKaptcha;

    @ApiOperation(value = "生成验证码")
    @GetMapping("/defaultKaptcha")
    public void defaultKaptcha(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse)
            throws Exception {
        byte[] captchaChallengeAsJpeg = null;
        ByteArrayOutputStream jpegOutputStream = new ByteArrayOutputStream();
        try {
            // 生产验证码字符串并保存到session中
            String createText = defaultKaptcha.createText();
            httpServletRequest.getSession().setAttribute("verificationCode", createText);
            // 使用生成的验证码字符串返回一个BufferedImage对象并转为byte写入到byte数组中
            BufferedImage challenge = defaultKaptcha.createImage(createText);
            ImageIO.write(challenge, "jpg", jpegOutputStream);
        } catch (IllegalArgumentException e) {
            httpServletResponse.sendError(HttpServletResponse.SC_NOT_FOUND);
            return;
        }

        // 定义response输出类型为image/jpeg类型，使用response输出流输出图片的byte数组
        captchaChallengeAsJpeg = jpegOutputStream.toByteArray();
        httpServletResponse.setHeader("Cache-Control", "no-store");
        httpServletResponse.setHeader("Pragma", "no-cache");
        httpServletResponse.setDateHeader("Expires", 0);
        httpServletResponse.setContentType("image/jpeg");
        ServletOutputStream responseOutputStream = httpServletResponse.getOutputStream();
        responseOutputStream.write(captchaChallengeAsJpeg);
        responseOutputStream.flush();
        responseOutputStream.close();
    }

    @ApiOperation(value = "校对验证码")
    @PostMapping("/checkVerificationCode")
    public Result<?> checkVerificationCode(@RequestParam(value = "verificationCode") String verificationCode, HttpServletRequest httpServletRequest) {
        String verificationCodeIn = (String) httpServletRequest.getSession().getAttribute("verificationCode");
        httpServletRequest.getSession().removeAttribute("verificationCode");
        if (StringUtils.isEmpty(verificationCodeIn) || !verificationCodeIn.equals(verificationCode)) {
            return Result.failureMsg("验证码错误，或已失效");
        }
        return Result.success();
    }
}

Swagger调用结果演示