使用XPath对象解析xml文件
1.DocumentBuilderFactory类 工厂API，使应用程序能从XML文档获取生成DOM对象树的解析器
其构造方法受保护，用newInstance()实例化
2.创建解析器
DocumentBuilder
使用这个类，应用程序员可以从XML获得一个Document。
这个类的实例可从DocumentBuilderFactory.newDocumentBuilder()方法获得。
一旦获得此类实例，可以从各种输入源解析XML。这些输入源是InputStreams,Files,URL和SAX InputSources。
----其构造方法是受保护的
public static void main(String[] args) throws Exception {
// 创建解析工厂
DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
// 创建解析器
DocumentBuilder documentBuilder = documentBuilderFactory.newDocumentBuilder();
// 通过解析器读取配置文件--返回Document对象树--org.w3c.dom.Document
Document doc = documentBuilder.parse("config/bookstore.xml");
// 创建XPath对象
XPathFactory xPathFactory = XPathFactory.newInstance();
XPath xPath = xPathFactory.newXPath();
/*
* 1.获取bookstore节点下的book属性category值为web下的第二个 title节点的文本内容
* bookstore-》book[@category='web'][2]-》title
* xpath路径：/bookstore/book[@category='web'][2]/title/text()
*/
String titleXpath = "/bookstore/book[@category='web'][2]/title/text()";
String titleVlue = (String) xPath.evaluate(titleXpath, doc, XPathConstants.STRING);
System.out.println("1:" + titleVlue);
/*
* 2.获取bookstore节点下book属性category值为web的title属性为en的节点内容
* xpath路径：/bookstore/book[@category='web']/title[@lang='en']/text() 选取属性为en
* 的title[@lang='en']
*/
String titleXpath2 = "/bookstore/book[@category='web']/title[@lang='en']/text()";
String titleValue2 = (String) xPath.evaluate(titleXpath2, doc, XPathConstants.STRING);
System.out.println("2:" + titleValue2);
/*
* 3.获取bookstore下book属性category值为cooking的title的lang属性的值
* xpath路径：/bookstore/book[@category='cooking']/title/@lang
*/
// 获取属性的值
String str1 = "/bookstore/book[@category='cooking']/title/@lang";
String shuxing = (String) xPath.evaluate(str1, doc, XPathConstants.STRING);
System.out.println("3:" + shuxing);
/*
* 4.获取bookstore节点下的所有book的节点集合 /bookstore/book
*/
// 返回值是节点集合
String str3 = "/bookstore/book";
NodeList all = (NodeList) xPath.evaluate(str3, doc, XPathConstants.NODESET);
// 开始遍历集合
for (int i = 0; i < all.getLength(); i++) {
// book节点
Element bookelt = (Element) all.item(i);// i是获取第几个
String titleValue = (String) xPath.evaluate("title", bookelt, XPathConstants.STRING);
String authorValue = (String) xPath.evaluate("author", bookelt, XPathConstants.STRING);
String yearValue = (String) xPath.evaluate("year", bookelt, XPathConstants.STRING);
String priceValue = (String) xPath.evaluate("price", bookelt, XPathConstants.STRING);
System.out.println(
"title:" + titleValue + " author:" + authorValue + " year:" + yearValue + " price:" + priceValue);
}
}
//config/bookstore.xml
<?xml version="1.0" encoding="UTF-8"?>
<!--
1.获取bookstore节点下的book属性category值为web下的第二个
title节点的文本内容
bookstore-》book[@category='web'][2]-》title
xpath路径：/bookstore/book[@category='web'][2]/title/text()
-->
<!--
2.获取bookstore节点下book属性category值为web的title属性为en的节点内容
xpath路径：/bookstore/book[@category='web']/title[@lang='en']
选取属性为en 的title[@lang='en']
-->
<!--
3.获取bookstore下book属性category值为cooking的title的lang属性的值
xpath路径：/bookstore/book[@category='cooking']/title/@lang
-->
<!--
4.获取bookstore节点下的所有book的节点集合
/bookstore/book
-->
<bookstore>
<book category="children">
<title lang="en">Harry Potter</title>
<author>J K. Rowling</author>
<year>2005</year>
<price>29.99</price>
</book>
<book category="cooking">
<title lang="en">Everyday Italian</title>
<author>Giada De Laurentiis</author>
<year>2005</year>
<price>30.00</price>
</book>
<book category="web">
<title lang="en">Learning XML</title>
<author>XJS</author>
<year>2019</year>
<price>79.88</price>
</book>
<book category="web">
<title lang="uk">Learning stack</title>
<author>XJS</author>
<year>2019</year>
<price>100.00</price>
</book>
</bookstore>