了解、解析、检索XML

<!-- version：XML默认的版本号码、该属性是必须存在的encoding：本XML文件的编码 -->
<?xml version="1.0" encoding="UTF-8"?>    
<data>
    <sender>喜羊羊</sender>
    <receiver>懒羊羊</receiver>
    <src>
    	 <addr>羊村</addr>
 	     <date>2022-11-11 11:11:11</date>
    </src>
    <current>狼堡</current>
    <dest>青青草原</dest>
</data>

<?xml version="1.0" encoding="UTF-8" ?>
<sheep>
    <name>懒羊羊</name>
    <age>3</age>
    <sex>男</sex>
    <hobby>睡觉</hobby>
    <sql>
        SELECT sheep FROM grassland WHERE age &gt; 2;
        <![CDATA[
            SELECT sheep FROM grassland WHERE age > 2;
        ]]>
    </sql>
</sheep>

<?xml version="1.0" encoding="UTF-8" ?>
</DOCTYPE 教室 SYSTEM "room.txt">
        <!-- 把规范导入 -->

<?xml version="1.0" encoding="UTF-8" ?>

<sheep>
    <name id = "1">懒羊羊</name>
    <age>3</age>
    <sex>男</sex>
    <hobby>睡觉</hobby>
    <sql>
        SELECT sheep FROM grassland WHERE age &gt; 2;
        <![CDATA[
            SELECT sheep FROM grassland WHERE age > 2;
        ]]>
    </sql>    
</sheep>

import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
import org.dom4j.io.SAXValidator;
import org.junit.Test;

import java.io.File;
import java.io.InputStream;
import java.util.List;


public class Dom4jTest1 {
    @Test
    public void parseXMLData() throws Exception {
        //1、创建一个Dom4j的解析器对象，代表了整个dom4j框架
        SAXReader saxReader = new SAXReader();
        // 2、把XML文件加载到内存中成为一个Document文档对象
        //Document document = saxReader.read(new File("demo5_XML/src/hello.xml"));

        //getResourceAsStream中的/是直接去src下寻找的文件
        InputStream is = Dom4jTest1.class.getResourceAsStream("/hello.xml");
        Document document = saxReader.read(is);

        // 获取根元素对象
        Element root = document.getRootElement();
        System.out.println(root.getName()); //根元素名字
        List<Element> elementList = root.elements();    //获取所有一级子元素
        //遍历
        for(Element element : elementList) {
            System.out.println(element.getName()+"   "+element.getTextTrim());
            //getText---不去空格  getTextTrim---去空格
        }
        //属性
        Element element = root.element("name");
        System.out.println(element.attribute("id").getName()+"-->"+element.attributeValue("id"));

    }
}

<!--    hello2.xml   -->
<?xml version="1.0" encoding="UTF-8" ?>

<sheep>
    <name id = "1">懒羊羊</name>
    <age>3</age>
    <sex>男</sex>
    <hobby>睡觉</hobby>

    <info>
        <name id = "2">小懒羊</name>
        <name id = "3">懒小羊</name>
        <hobby>吃草</hobby>
        <hobby>吃冰淇淋</hobby>
    </info>

    <sql>
        SELECT sheep FROM grassland WHERE age &gt; 2;
        <![CDATA[
            SELECT sheep FROM grassland WHERE age > 2;
        ]]>
    </sql>

</sheep>

import org.dom4j.Attribute;
import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.Node;
import org.dom4j.io.SAXReader;
import org.junit.Test;

import java.util.List;

//绝对路径
public class XpathTest3 {
    @Test
    public void parse01() throws Exception {
        //1.创建解析器对象
        SAXReader saxReader = new SAXReader();
        //2.把XML加载成Document文档对象
        Document document = saxReader.read(XpathTest3.class.getResourceAsStream("/hello2.xml"));
        //3.检索全部的名称
        List<Node> nameNodes = document.selectNodes("/sheep/info/name");
        for (Node nameNode : nameNodes) {
            Element  nameEle = (Element) nameNode;
            System.out.println(nameEle.getTextTrim());
        }
    }
}

import org.dom4j.Attribute;
import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.Node;
import org.dom4j.io.SAXReader;
import org.junit.Test;

import java.util.List;

//相对路径
public class XpathTest3 {
    @Test
    public void parse02() throws Exception {
        //1.创建解析器对象
        SAXReader saxReader = new SAXReader();
        //2.把XML加载成Document文档对象
        Document document = saxReader.read(XpathTest3.class.getResourceAsStream("/hello2.xml"));
        Element root = document.getRootElement();
        //3.检索全部的名称
        List<Node> hobbyNodes = root.selectNodes("./info/hobby");    //.代表了当前元素
        for (Node hobbyNode : hobbyNodes) {
            Element  nameEle = (Element) hobbyNode;
            System.out.println(nameEle.getTextTrim());
        }
    }
}

import org.dom4j.Attribute;
import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.Node;
import org.dom4j.io.SAXReader;
import org.junit.Test;

import java.util.List;

public class XpathTest3 {
    @Test
    public void parse03() throws Exception {
        //1.创建解析器对象
        SAXReader saxReader = new SAXReader();
        //2.把XML加载成Document文档对象
        Document document = saxReader.read(XpathTest3.class.getResourceAsStream("/hello2.xml"));
        //3.检索数据
        List<Node> nameNodes = document.selectNodes("//name");
        List<Node> hobbyNodes = document.selectNodes("//info//hobby");
        for (Node nameNode : nameNodes) {
            Element  nameEle = (Element) nameNode;
            System.out.println(nameEle.getTextTrim());
        }
        for (Node hobbyNode : hobbyNodes) {
            Element  nameEle = (Element) hobbyNode;
            System.out.println(nameEle.getTextTrim());
        }
    }
}

import org.dom4j.Attribute;
import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.Node;
import org.dom4j.io.SAXReader;
import org.junit.Test;

import java.util.List;

public class XpathTest3 {
   @Test
    public void parse04() throws Exception {
        //1.创建解析器对象
        SAXReader saxReader = new SAXReader();
        //2.把XML加载成Document文档对象
        Document document = saxReader.read(XpathTest3.class.getResourceAsStream("/hello2.xml"));
        //3.检索数据
        List<Node> nodes = document.selectNodes("//name[@id]");
        for (Node node : nodes) {
            Element ele = (Element) node;
            System.out.println(ele.getTextTrim() + "--->" + ele.attributeValue("id"));
        }
        // 查询name元素（包含id属性的）
        Node node = document.selectSingleNode("//name[@id=1]");
        Element ele = (Element) node;
        System.out.println(ele.getTextTrim());
    }
}