private String doUserLogin(String userName, String userPass) {
		String outputJson = "";
		UserInfo userInfo = UserDAO.validateUserInfo(userName, userPass);
		boolean status = userInfo == null ? false : true;
		String message = userInfo == null ? "failed to login"
				: "success to login";
		UserinfoWrapper userOuput = new UserinfoWrapper();
		userOuput.setUserInfo(userInfo);
		userOuput.setStatus(status);
		userOuput.setMessage(message);
		outputJson = Gson.toJson(userOuput);
		return outputJson;
	}