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

// 生成驗證碼
String code = kaptchaProducer.createText();

BufferedImage kaptchaImage = kaptchaProducer.createImage(code);

ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
ImageIO.write(kaptchaImage, "jpg", outputStream);
String base64Img = Base64.getEncoder().encodeToString(outputStream.toByteArray());

Map<String, String> imgMap = new HashMap<>();
imgMap.put(key, "data:image/jpeg;base64," + base64Img);

{ "captchaKey": "data:image/jpeg;base64,/9j/4AAQSkZJRgA..." }

Map<String, String> cacheMap = new HashMap<>();
cacheMap.put(CODE, code.toUpperCase());
captchaCache.putCaptcha(key, cacheMap);

@Override
public boolean putCaptcha(String key, Map<String, String> value) {
    try {
        cache.put(key, JSONObject.fromObject(value).toString());
    } catch (Exception ex) {
        return false;
    }
    return true;
}

		if(StringUtil.isEmpty(key)) {
			throw new BadRequestAlertException(ErrorConstants.CAPTCHA_TYPE, "The information of captcha is missing", "captcha.header", "missing");
		}

Map<String, String> validateMap = captchaCache.getCaptcha(key);

captchaCache.deleteCaptcha(key);

		if(captcha.get(CODE).equalsIgnoreCase(validateMap.get(CODE))){
			return true;
		}