dom4j怎么获得指定名称的节点信息

<?xml version="1.0" encoding="utf-8" ?>

 <MgUtil>

    <db_config>

        <db_driver>oracle.jdbc.driver.OracleDriver</db_driver>

        <db_url>dbc:oracle:thin:@172.16.1.101:1521:orcl</db_url>

        <db_user>zdyn</db_user>

        <db_password>zdyn</db_password>

    </db_config>

    <relationFactory>

        <classInfo></classInfo>

    </relationFactory>

 </MgUtil>

String xml ="...";

Document doc = DocumentHelper.parseText(xml);

Element root = doc.getRootElement();

Element db_config = root.element("db_config");

Element db_driver = db_config.element("db_driver");

String val_db_driver= db_driver.getTextTrim();