Xapth 添加注释头

private static void updateMybatisXml(String url, String username, String password) {
  DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
  dbf.setIgnoringElementContentWhitespace(false);
  try {
    DocumentBuilder db = dbf.newDocumentBuilder();
    Document xmldoc = db.parse(xmlPath);

    Element root = xmldoc.getDocumentElement();
    Element per = (Element) selectSingleNode("/configuration/environments/environment/dataSource", root);
    NodeList properties = per.getElementsByTagName("property");

    Element urlElement = (Element) properties.item(1);
    urlElement.setAttribute("value", url);
    Element userNameElement = (Element) properties.item(2);
    userNameElement.setAttribute("value", username);
    Element passwordElement = (Element) properties.item(3);
    passwordElement.setAttribute("value", password);

    TransformerFactory factory = TransformerFactory.newInstance();
    Transformer transformer = factory.newTransformer();
    DOMImplementation domImpl = xmldoc.getImplementation();
    DocumentType doctype = domImpl.createDocumentType("configuration",
        "-//mybatis.org//DTD Config 3.0//EN",
        "http://mybatis.org/dtd/mybatis-3-config.dtd");
    transformer.setOutputProperty(OutputKeys.DOCTYPE_PUBLIC, doctype.getPublicId());
    transformer.setOutputProperty(OutputKeys.DOCTYPE_SYSTEM, doctype.getSystemId());
    transformer.transform(new DOMSource(xmldoc), new StreamResult(new File(xmlPath)));
  } catch (Exception e) {
    System.out.println(e.getMessage());
  }
}

public static Node selectSingleNode(String express, Element source) {
  Node result = null;
  XPathFactory xpathFactory = XPathFactory.newInstance();
  XPath xpath = xpathFactory.newXPath();
  try {
    result = (Node) xpath.evaluate(express, source, XPathConstants.NODE);
    System.out.println(result);
  } catch (XPathExpressionException e) {
    System.out.println(e.getMessage());
  }

  return result;
}