static void closeTx(Connection conn) {
        try {
            if (conn != null) {
                if (conn.isReadOnly()) {
                    conn.setReadOnly(false);  // restore NOT readOnly before return to pool
                }
                conn.close();
            }
        } catch (SQLException e) {
            LOGGER.error(e.getMessage(), e);
        } finally {
            TRANSACT_CONN.set(null);
        }
    }
@author Robert HG (254963746@qq.com) on 5/20/15.
lts-core/src/main/java/com/github/ltsopensource/store/jdbc/TxConnectionFactory.java