java-xpath学习

Posted 2020-10-31

/**

• 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 {

    @Test
    public 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("=================");
        }

    }

    @Test
    public 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());

    }

    @Test
    public 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());
    }

    @Test
    public 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