第一步:通过 DocumentBuilderFactory 获取解析工厂
DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
第二步:获取解析器
DocumentBuilder builder = builderFactory.newDocumentBuilder();
第三步:通过解析的 parser 方法获取 Document 对象
Document document = builder.parse(new File(“books.xml”));
第四步:获取 XPath 对象
XPath xPath = XPathFactory.newInstance().newXPath()