java - 我对 XPath 做错了什么？

Question

我正在尝试将 xsd 架构作为 xml 文档进行操作，我相信这应该不是问题。但是面对 XPath 的麻烦。无论我尝试什么 XPath，它都不会返回任何内容。尝试使用或不使用 namespace 但没有成功。请帮助我了解我做错了什么？

我的 xml 是:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.mydomain.com" xmlns="http://www.mydomain.com" elementFormDefault="qualified">

  <xs:complexType name="Label">
    <xs:choice maxOccurs="unbounded" minOccurs="0">
      <xs:element name="Listener"/>
    </xs:choice>
  </xs:complexType>

</xs:schema>

应用程序代码是:

DocumentBuilderFactory domFactory = DocumentBuilderFactory.newInstance();
domFactory.setValidating(false);
domFactory.setNamespaceAware(true);
domFactory.setIgnoringComments(true);
domFactory.setIgnoringElementContentWhitespace(true);

try {
    DocumentBuilder builder = domFactory.newDocumentBuilder();
    Document dDoc = builder.parse("C:/Temp/test.xsd");

    // This part works
    Node rootNode = dDoc.getElementsByTagName("xs:schema").item(0);
    System.out.println(rootNode.getNodeName());

    // This part doesn't work
    XPath xPath1 = XPathFactory.newInstance().newXPath();
    NodeList nList1 = (NodeList) xPath1.evaluate("//xs:schema", dDoc, XPathConstants.NODESET);  
    System.out.println(nList1.item(0).getNodeName());

    // This part doesn't work
    XPath xPath2 = XPathFactory.newInstance().newXPath();
    NodeList nList2 = (NodeList) xPath2.evaluate("//xs:element", rootNode, XPathConstants.NODESET); 
    System.out.println(nList2.item(0).getNodeName());

}catch (Exception e){
    e.printStackTrace();
}

Answer 1

使用 XPath.setNamespaceContext() 设置命名空间上下文。这会将 xs 前缀绑定(bind)到 http://www.w3.org/2001/XMLSchema 命名空间。