public AccountServiceError addUser(String login, String password) {
        if (isConnectionClosed())
            openConnection();

        if (isConnectionClosed())
            return new AccountServiceError(AccountServiceError.Type.DB_noConnection);

        UserDataSetDAO dao = new UserDataSetDAO(dbconn);

        UserDataSet user = null;
        try {
            user = dao.find("login", login);
        } catch(SQLException e) {
            e.printStackTrace();
        }

        if (user != null)
            return new AccountServiceError(AccountServiceError.Type.Sigiup_userAlreadyExists);

        user = new UserDataSet(login, password);
        boolean result = dao.save(user);
        if (result)
            return new AccountServiceError();
        return new AccountServiceError(AccountServiceError.Type.Signup_badUserForm);
    }