public Connection getConn() {
        try {
            if (conn == null || conn.isClosed()) {
                conn = DriverManager.getConnection(
                        "jdbc:mysql://124.173.158.2:3306/tianbao?autoReconnect=true&useUnicode=true&characterEncoding=utf-8",
                        "tianbao_f", "daige3");
            }
        } catch (SQLException e) {
            e.printStackTrace();
            System.out.println("getConnection()错误");
        }
        return conn;
    }