private void initialize() throws Exception {
        if (props.propertyNames().hasMoreElements()) {
            String url = props.getProperty("db.url");
            String user = props.getProperty("db.user");
            String passwd = props.getProperty("db.passwd");

            if (url != null && user != null && passwd != null) {
                try {
                    con = DriverManager.getConnection(url, user, passwd);
                } catch (SQLException ex) {
                    Logger.getLogger(DataManager.class.getName()).log(Level.SEVERE, null, ex);
                }
            }
        } else {
            throw new Exception("Properties file is missing or invalid.");
        }
    }