如果要定位某个XML文档中的一段特性信息，那么通过遍历DOM树的众多节点来进行查找显得有些麻烦。XPath是的访问树节点变得很容易。
需要先了解Java XML解析，可以参考Java验证解析XML
场景
<bookstore>
<book id="book1">
<name>Java 核心技术</name>
<author>Cornell </author>
<year>2014</year>
<price>89</price>
</book>
<book id="book2">
<name>深入浅出MyBatis</name>
<author>杨开振</author>
<year>2016</year>
<price>69</price>
</book>
<book id="book3">
<name>Java RESTful Web Service实战</name>
<author>韩陆</author>
<year>2016</year>
<price>59</price>
</book>
</bookstore>
如果需要得到author节点，可以通过XPath表达式/bookstore/book/author来得到所有的author节点。java代码如下。
/**
* @author gethin
* @version 创建时间：2018年4月8日 下午3:17:04
* 类说明
*/
public class ReadXMLByDOMWithXpath {
private static DocumentBuilderFactory dBuilderFactory = null;
private static DocumentBuilder dBuilder = null;
private static XPathFactory xPathFactory = null;
private static XPath xPath = null;
static {
try {
/**
* 要读入一个XML文档，首先要有一个DocumentBuilder对象 可以从DocumentBuilderFactory中得到这个对象
*/
dBuilderFactory = DocumentBuilderFactory.newInstance();
//设置验证
dBuilderFactory.setValidating(true);
//忽略空白字符节点
dBuilderFactory.setIgnoringElementContentWhitespace(true);
dBuilder = dBuilderFactory.newDocumentBuilder();
xPathFactory = XPathFactory.newInstance();
xPath = xPathFactory.newXPath();
dBuilder.setErrorHandler(new ErrorHandler() {
public void warning(SAXParseException exception) throws SAXException {
throw exception;
}
public void fatalError(SAXParseException exception) throws SAXException {
// TODO Auto-generated method stub
throw exception;
}
public void error(SAXParseException exception) throws SAXException {
// TODO Auto-generated method stub
throw exception;
}
});
} catch (ParserConfigurationException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
//获得所有的author节点并输出
public static void showAuthorByXPath(String fileName) throws SAXException, IOException, XPathExpressionException {
Document document = dBuilder.parse(fileName);
NodeList nodeList = (NodeList) xPath.evaluate("/bookstore/book/author", document, XPathConstants.NODESET);
for (int i = 0; i < nodeList.getLength(); i++) {
Element author = (Element) nodeList.item(i);
System.out.println(author.getTextContent().trim());
}
}
public static List<Book> listBooksWithXpath(String fileName)
throws XPathExpressionException, SAXException, IOException {
List<Book> books = new ArrayList<Book>();
// 可通过DocumentBuilder对象的parse()方法读入整个文档
Document document = dBuilder.parse(fileName);
// 获得所有book节点
NodeList nodeList = (NodeList) xPath.evaluate("/bookstore/book", document, XPathConstants.NODESET);
for (int i = 0; i < nodeList.getLength(); i++) {
Element bookElement = (Element) nodeList.item(i);
// 获得该book节点下的所有属性节点
NodeList bookAttribute = bookElement.getChildNodes();
// 用来存储第i个节点的内容
List<String> bookContent = new ArrayList<String>();
Book book = new Book();
book.setId(Integer.parseInt(bookElement.getAttribute("id").replace("book", "").trim()));
for (int j = 0; j < bookAttribute.getLength(); j++) {
Element atturbute = (Element) bookAttribute.item(j);
bookContent.add(atturbute.getTextContent().trim());
}
book.setName(bookContent.get(0));
book.setAuthor(bookContent.get(1));
book.setYear(Integer.parseInt(bookContent.get(2)));
book.setPrice(Integer.parseInt(bookContent.get(3)));
books.add(book);
}
return books;
}
public static void main(String args[]) {
String fileName = "./src/main/java/com/gethin/xmlparser/bookstore.xml";
try {
List<Book> books = ReadXMLByDOMWithXpath.listBooksWithXpath(fileName);
for (Book book : books) {
System.out.println(book);
}
showAuthorByXPath(fileName);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
运行截图：
DOM结合XPath解析XML文档
请参考，源码github链接
