StringBuilder sb = new StringBuilder()
SecureRandom secureRandom = null;
try {
secureRandom = SecureRandom.getInstance("SHA1PRNG");
} catch (NoSuchAlgorithmException e) {
throw new ServiceException("獲取SecureRandom隨機數失敗");
}
sb.append(secureRandom.nextInt(999999));
return sb.toString();