2021-12-02 XML学习

一、基本概念

1. xml元素：
   元素是指从开始标签到结束标签的内容

2. xml文档必须有根元素

3. 这个符号里面的不会被解析

    <![CDATA[
    
    ]]>

二、xml解析

两种xml解析技术，DOM和Sax（过时）

第三方解析： jdom在dom基础上进行封装，dom4j又进行封装，puu主要用在Android

三、Dom4j类库的使用–进行xml解析

<books>
    <book sn="SN12341232">
        <name>book1name>
        <price>9.9price>
        <author>班主任author>
    book>
    <book sn="SN12341231">
        <name>book2name>
        <price>99.99price>
        <author>班长author>

    book>
books>

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

import java.math.BigDecimal;
import java.util.List;

public class Dom4jTest {
     
    @Test
    public void test1() throws DocumentException {
     
        //创建一个SaxReader输入流，去读取xml配置文件，生成Document对象
        SAXReader saxReader=new SAXReader();
        Document document=saxReader.read("src/books.xml");
        System.out.println(document);
    }

    @Test
    public void test2 () throws Exception
    {
     
        //1. 读取books.xml文件
        SAXReader reader=new SAXReader();
        Document document=reader.read("src/books.xml");//注意：在Junit测试中，相对路径时从模块名开始算
        //2. 通过document对象获取根元素
        Element rootElement = document.getRootElement();
        System.out.println(rootElement);
        //3. 通过根元素获取book标签对象
        //element()和elements()都是通过标签名查找子元素
        List<Element> books = rootElement.elements("book");
		 //4. 遍历，处理每个book标签转换为Book类

        for(Element book:books)
        {
     
            //asXML 把标签对象转换为标签字符串
            //System.out.println(book.asXML());
            Element nameElement=book.element("name");
            //getText 获取标签中的文本内容
            String nameText=nameElement.getText();
            // 直接获取指定标签名
            String priceText = book.elementText("price"); // Double.parseDouble(priceText)  String->double
            String authorText=book.elementText("author");
            String snValue=book.elementText("sn");
            System.out.println(new Book(snValue,nameText,new BigDecimal(priceText),authorText));


        }

       

    }


}

import java.math.BigDecimal;

public class Book {
     
    private String sn;
    private String name;
    private BigDecimal price;
    private String author;
    public Book()
    {
     

    }

    public Book(String sn, String name, BigDecimal price, String author) {
     
        this.sn = sn;
        this.name = name;
        this.price = price;
        this.author = author;
    }



    public String getSn() {
     
        return sn;
    }

    public void setSn(String sn) {
     
        this.sn = sn;
    }

    public String getName() {
     
        return name;
    }

    public void setName(String name) {
     
        this.name = name;
    }

    public BigDecimal getPrice() {
     
        return price;
    }

    public void setPrice(BigDecimal price) {
     
        this.price = price;
    }

    public String getAuthor() {
     
        return author;
    }

    public void setAuthor(String author) {
     
        this.author = author;
    }
}