class DBUserGroupCallbackImpl extends AbstractUserGroupInfo implements UserGroupCallback {

	public boolean existsUser(String userId) {
		if (userId == null) {
			throw new IllegalArgumentException("UserId cannot be null");
		}
		return checkExistence(this.config.getProperty(PRINCIPAL_QUERY), userId);
	}

	public  DBUserGroupCallbackImpl(boolean activate);
	public  DBUserGroupCallbackImpl(Properties config);

}