/**

• 使用xpath技术取得xml文件中任意级别下的内容 基于dom4j的xpath技术
• 1)能够在xml文件中，快速定位需要元素，无需从根元素一个一个的导航到需要的子元素
• Document.selectNodes()：取得所有符合xpath格式的元素
• Document.selectSingleNode()：取得所有符合xpath格式的元素的第一个元素
• Node类型是Element/Text/Attribute/Document/...类型的父接口
• */

import java.io.File;
import java.util.List;
import java.util.Scanner;import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXContentHandler;
import org.dom4j.io.SAXReader;
import org.junit.Test;/*** 使用xpath技术取得xml文件中任意级别下的内容 基于dom4j的xpath技术* 1)能够在xml文件中，快速定位需要元素，无需从根元素一个一个的导航到需要的子元素* Document.selectNodes()：取得所有符合xpath格式的元素* Document.selectSingleNode()：取得所有符合xpath格式的元素的第一个元素* Node类型是Element/Text/Attribute/Document/...类型的父接口* */public class Xpath {@Testpublic void xpathtest() throws Exception {SAXReader reader = new SAXReader();Document document = reader.read(new File("src/day2/domx/car.xml"));String xpath = "//单价";List<Element> elementList = document.selectNodes(xpath);for (Element e : elementList) {System.out.println(e.getText());System.out.println("=================");}}@Testpublic void xpathtest1() throws Exception {SAXReader reader = new SAXReader();Document document = reader.read(new File("src/day2/domx/car.xml"));String xpath = "//单价";List<Element> elementList = document.selectNodes(xpath);System.out.println("第二辆汽车的单价是：" + elementList.get(1).getText());}@Testpublic void xpathtest2() throws Exception {SAXReader reader = new SAXReader();Document document = reader.read(new File("src/day2/domx/car.xml"));String xpath = "//单价";Element element = (Element) document.selectSingleNode(xpath);System.out.println("第一辆汽车的单价是：" + element.getText());}@Testpublic void login() throws Exception {// 读取用户在键盘的输入信息Scanner scanner = new Scanner(System.in);System.out.println("用户名：");String username = scanner.nextLine();System.out.print("密码：");String password = scanner.nextLine();// System.out.println(username+":"+password);//解析XML文件，并查询指定的元素SAXReader saxReader = new SAXReader();Document document = saxReader.read(new File("src/day2/domx/users.xml"));String xpath = "//user[@username='"+username+"' and @password='"+password+"']" ;Element element =   (Element) document.selectSingleNode(xpath);if(element != null){System.out.println("登陆成功");}else{System.out.println("登陆失败");}}}

user.xml

<?xml version="1.0" encoding="UTF-8"?>
<root><user id = "id001" username ="liwen" password="123456"></user><user id = "id002" username ="python" password="23456"></user>
</root>

结果：
用户名：
liwen
密码：123456
登陆成功