// 构建一个 Gmail风格 工厂并生成验证码
final GmailFactory factory = new GmailFactory();
// 构建一个数学计算验证码工厂
// final MathFactory factory = new MathFactory();
final Captcha captcha = factory.getCaptcha();

// 获取验证码图片
final BufferedImage image = captcha.getChallenge();

// 验证响应是否正确
if(captcha.validate("123456")) {
    // TODO 验证码响应正确
} else {
    // TODO 验证码响应不正确
}

// 构建使用 ehcache 进行存储的 captcha store, 也可以选用 redis 或自行实现 CaptchaStore 接口
final net.sf.ehcache.CacheManager cacheManager = net.sf.ehcache.CacheManager.getInstance();
final CaptchaStore captchaStore = new EhcacheStore(cacheManager);
final CaptchaFactory captchaFactory = new DefaultFactory();

final CaptchaService captchaService = new DefaultManageableCaptchaService(captchaStore, captchaFactory);
final String captchaToken = ...(自行生成 token 即可);

// 为 token 生成验证码
BufferedImage image = captchaService.getChallengeForId(captchaToken);

// 验证 token 对应相应是否正确
captchaService.validateResponseForId(captchaToken, "123");