public static void main(String[] args) throws JDOMException, IOException
    {
        SAXBuilder builder = new    SAXBuilder();
        Document doc = builder.build(new File("abc.xml"));
        Text txt = (Text) XPath.selectSingleNode(doc,"gmd:message/gmd:yxxid/text()");
            System.out.println(txt.getText());
    }

------解决方案--------------------
学习

------解决方案--------------------
JDOM本身支持命名空间的提取，在取节点时再带上命名空间这个参数即可。