XML解析方式分为两种：dom和sax
dom：（Document Object Model,即文档对象模型）是W3C组织推荐的解析XML的一种方式。
sax：（Simple API for XML)不是官方标准，但它是XML社区事实上的标准，几乎所有的XML解析器都支持它。
dom和sax解析方法的区别：
1.dom解析的优点：对文档CRUD比较方便；缺点：占用内存比较大
2.sax解析的优点：占用内存少，解析速度快；取点：只适合做文档读取，不适合做文档的CRUD
XML解析开发包：Jaxp（sun）、Jdom、dom4j
使用JAXP对XML文档进行DOM解析
核心代码：
//1,创建工厂
DocumentBuilderFactory factor=DocumentBuilderFactory.newInstance();
//2,得到dom解析器
DocumentBuilder builder=factor.newDocumentBuilder();
//3,解析xml文档，得到代表文档的document
builder.parse("src/book.xml");
增，删，改 需要将更新后的内容在写到xml中
TransformerFactory tffactory=TransformerFactory.newInstance();
Transformer tf=tffactory.newTransformer();
tf.transform(new DOMSource(document),new StreamResult(new FileOutputStream("src/book.xml")));
book.xml
<?xml version="1.0" encoding="UTF-8" standalone="no"?> <书架> <span style="white-space:pre"> </span><书> <span style="white-space:pre"> </span><书名 name="XXXX">Java基础</书名> <span style="white-space:pre"> </span><进价>40元</进价> <span style="white-space:pre"> </span><零售价>159元</零售价> <span style="white-space:pre"> </span> <span style="white-space:pre"> </span></书> <span style="white-space:pre"> </span><书> <span style="white-space:pre"> </span><书名>Java从入门到精通</书名> <span style="white-space:pre"> </span><进价>90元</进价> <span style="white-space:pre"> </span><零售价>30元</零售价> <span style="white-space:pre"> </span></书> </书架>
Demo.java
package com.yong.xml;
import java.io.FileOutputStream;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import org.junit.Test;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
//使用dom方式对xml文档进行crud
public class Demo2 {
@Test
//读取book.xml文档中：<书名>Java从入门到精通</书名> 节点中的值
public void read1() throws Exception
{
DocumentBuilderFactory factory=DocumentBuilderFactory.newInstance();
DocumentBuilder builder=factory.newDocumentBuilder();
Document document=builder.parse("src/book.xml");
NodeList list =document.getElementsByTagName("书名");
//dom解析下，xml文档的每一个组成部分都会用一个对象表示，不管什么对象，
//都是Node的子类，所以在开发中科院把获取到的任意节点都当做Node对待
Node node=list.item(1);
String content=node.getTextContent();
System.out.println(content); //打印结果：Java从入门到精通
}
@Test
//得到book.xml文档中的所有标签
public void read2() throws Exception
{
DocumentBuilderFactory factory=DocumentBuilderFactory.newInstance();
DocumentBuilder builder=factory.newDocumentBuilder();
Document document=builder.parse("src/book.xml");
//得到根节点
Node root=document.getElementsByTagName("书架").item(0);
list(root);
}
private void list(Node node) {
if(node instanceof Element)
{
System.out.println(node.getNodeName());
}
NodeList list=node.getChildNodes();
for(int i=0;i<list.getLength();i++)
{
Node child=list.item(i);
list(child);// 打印出各个标签：书架 书 书名 进价 零售价 书 书名 进价 零售价
}
}
@Test
//得到book.xml中标签内的属性值 <书名 name="XXXX">Java基础</书名>
public void read3() throws Exception
{
DocumentBuilderFactory factory=DocumentBuilderFactory.newInstance();
DocumentBuilder builder=factory.newDocumentBuilder();
Document document=builder.parse("src/book.xml");
Element bookname=(Element) document.getElementsByTagName("书名").item(0);
String value=bookname.getAttribute("name");
System.out.println(value); //打印结果：XXXX
}
@Test
//向book.xml中添加 <团购>12元</团购>
public void add() throws Exception
{
DocumentBuilderFactory factory=DocumentBuilderFactory.newInstance();
DocumentBuilder builder=factory.newDocumentBuilder();
Document document=builder.parse("src/book.xml");
//创建节点
Element price=document.createElement("团购");
price.setTextContent("12元");
//把创建的节点挂到第一本书上
Element book=(Element) document.getElementsByTagName("书").item(0);
book.appendChild(price);
//把更新后内存写回到xml文档
TransformerFactory tffactory=TransformerFactory.newInstance();
Transformer tf=tffactory.newTransformer();
tf.transform(new DOMSource(document),new StreamResult(new FileOutputStream("src/book.xml")));
}
@Test
//向book.xml中指定位置上添加节点
public void add2() throws Exception
{
DocumentBuilderFactory factory=DocumentBuilderFactory.newInstance();
DocumentBuilder builder=factory.newDocumentBuilder();
Document document=builder.parse("src/book.xml");
//创建节点
Element price=document.createElement("批发");
price.setTextContent("8元");
//得到参考点
Element refNode=(Element) document.getElementsByTagName("零售价").item(0);
//得到要挂崽的节点
Element book=(Element) document.getElementsByTagName("书").item(0);
//往book节点的指定位置插崽
book.insertBefore(price,refNode);
//把更新后内存写回到xml文档
TransformerFactory tffactory=TransformerFactory.newInstance();
Transformer tf=tffactory.newTransformer();
tf.transform(new DOMSource(document),new StreamResult(new FileOutputStream("src/book.xml")));
}
@Test
//向book.xml文档节点上添加属性， <书名 >Java基础</书名>上添加 name="XXXX"属性
public void addAttr() throws Exception
{
DocumentBuilderFactory factory=DocumentBuilderFactory.newInstance();
DocumentBuilder builder=factory.newDocumentBuilder();
Document document=builder.parse("src/book.xml");
Element bookname=(Element) document.getElementsByTagName("书名").item(0);
bookname.setAttribute("name","XXXX");
//把更新后内存写回到xml文档
TransformerFactory tffactory=TransformerFactory.newInstance();
Transformer tf=tffactory.newTransformer();
tf.transform(new DOMSource(document),new StreamResult(new FileOutputStream("src/book.xml")));
}
@Test
//删除book.xml中的指定节点方法一
public void delete1() throws Exception
{
DocumentBuilderFactory factory=DocumentBuilderFactory.newInstance();
DocumentBuilder builder=factory.newDocumentBuilder();
Document document=builder.parse("src/book.xml");
//得到要删除的节点
Element e=(Element) document.getElementsByTagName("售价").item(0);
//得到要删除的节点的爸爸
Element book=(Element) document.getElementsByTagName("书").item(0);
//爸爸删崽
book.removeChild(e);
//把更新后内存写回到xml文档
TransformerFactory tffactory=TransformerFactory.newInstance();
Transformer tf=tffactory.newTransformer();
tf.transform(new DOMSource(document),new StreamResult(new FileOutputStream("src/book.xml")));
}
@Test
//删除book.xml中的指定节点方法二
public void delete2() throws Exception
{
DocumentBuilderFactory factory=DocumentBuilderFactory.newInstance();
DocumentBuilder builder=factory.newDocumentBuilder();
Document document=builder.parse("src/book.xml");
//得到要删除的节点
Element e=(Element) document.getElementsByTagName("售价").item(0);
e.getParentNode().removeChild(e);
//把更新后内存写回到xml文档
TransformerFactory tffactory=TransformerFactory.newInstance();
Transformer tf=tffactory.newTransformer();
tf.transform(new DOMSource(document),new StreamResult(new FileOutputStream("src/book.xml")));
}
@Test
//更改book.xml中节点的属性
public void update() throws Exception
{
DocumentBuilderFactory factory=DocumentBuilderFactory.newInstance();
DocumentBuilder builder=factory.newDocumentBuilder();
Document document=builder.parse("src/book.xml");
//得到要修改的节点
Element e=(Element) document.getElementsByTagName("售价").item(0);
e.setTextContent("2201元");
//把更新后内存写回到xml文档
TransformerFactory tffactory=TransformerFactory.newInstance();
Transformer tf=tffactory.newTransformer();
tf.transform(new DOMSource(document),new StreamResult(new FileOutputStream("src/book.xml")));
}
}
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