XML编程:利用java程序去增删改查(CRUD)xml中的数据

解析思想:
dom解析
sax解析
基于这两种解析思想市面上就有了很多的解析api
sun jaxp既有dom方式也有sax方式,并且这套解析api已经加入到j2se的规范中,意味这不需要导入任何第三方开发包就可以直接使用这种解析方式.但是这种解析方式效率低下,没什么人用.
dom4j 可以使用dom方式高效的解析xml.
pull

!!dom4j

导入开发包,通常只需要导入核心包就可以了,如果在使用的过程中提示少什么包到lib目录下在导入缺少的包即可

解析的xml文件：

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

<书架> 
  <书 出版社="北京出版社"> 
    <书名>Java就业培训教程</书名>  
    <作者>张孝祥</作者>  
    <售价>50.00元</售价>  
    <特价>20.0元</特价> 
  </书>  
  <书> 
    <书名>JavaScript网页开发</书名>  
    <作者>张孝祥</作者>  
    <售价>40.00元</售价> 
  </书> 
</书架>

SAX解析方式：

package sax;

import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;

import org.xml.sax.Attributes;
import org.xml.sax.ContentHandler;
import org.xml.sax.Locator;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.DefaultHandler;

public class SaxDemo1 {
	public static void main(String[] args) throws Exception {
		//解析器工厂
		SAXParserFactory factory=SAXParserFactory.newInstance();
		//sax解析器
		SAXParser parser = factory.newSAXParser();
		//获取读取器
		XMLReader reader = parser.getXMLReader();
		//注册事件
		reader.setContentHandler(new MyContentHander2());
		//解析xml文档
		reader.parse("book.xml");
	}
}
//读取第二本书的价格
class MyContentHander2 extends DefaultHandler{
	private String eleName="";
	private int count=0;
	@Override
	public void startElement(String uri,String localName,String qName,Attributes attributes) throws SAXException {
		super.startElement(uri,localName,qName,attributes);
		this.eleName=qName;
		
	}

	@Override
	public void endElement(String uri,String qName)
			throws SAXException {
		super.endElement(uri,qName);
		eleName="";
	}

	@Override
	public void characters(char[] ch,int start,int length)
			throws SAXException {
		super.characters(ch,start,length);
		if("书名".equals(eleName)&&++count==2){
			System.out.println(new String(ch,length));
		}
	}
	
}
class MyContentHander implements ContentHandler{

	@Override
	public void setDocumentLocator(Locator locator) {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void startDocument() throws SAXException {
		// TODO Auto-generated method stub
		System.out.println("开始读取文档....");
		
	}

	@Override
	public void endDocument() throws SAXException {
		// TODO Auto-generated method stub
		System.out.println("结束读取文档....");
		
	}

	@Override
	public void startPrefixMapping(String prefix,String uri)
			throws SAXException {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void endPrefixMapping(String prefix) throws SAXException {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void startElement(String uri,Attributes atts) throws SAXException {
		// TODO Auto-generated method stub
		System.out.println("发现开始标签,"+qName);
		
	}

	@Override
	public void endElement(String uri,String qName)
			throws SAXException {
		// TODO Auto-generated method stub
		System.out.println("结束考试标签,"+qName);
	}

	@Override
	public void characters(char[] ch,int length)
			throws SAXException {
		// TODO Auto-generated method stub
		System.out.println(new String(ch,length));
	}

	@Override
	public void ignorableWhitespace(char[] ch,int length)
			throws SAXException {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void processingInstruction(String target,String data)
			throws SAXException {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void skippedEntity(String name) throws SAXException {
		// TODO Auto-generated method stub
		
	}
	
}

dom4j解析：

package dom4j;

import java.io.FileOutputStream;
import java.util.List;

import org.dom4j.Attribute;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.DocumentHelper;
import org.dom4j.Element;
import org.dom4j.io.OutputFormat;
import org.dom4j.io.SAXReader;
import org.dom4j.io.XMLWriter;
import org.junit.Test;
public class Dom4jDemo {
	@Test
	public void attr() throws Exception{
		SAXReader reader=new SAXReader();
		Document doc = reader.read("book.xml");
		Element rootElement = doc.getRootElement();
		Element attribute = rootElement.element("书").addAttribute("出版社","北京出版社");
		
		XMLWriter writer = new XMLWriter(new FileOutputStream("book.xml"),OutputFormat.createPrettyPrint());
		writer.write(doc);
		writer.close();
	}
	@Test
	public void add()throws Exception{
		SAXReader reader=new SAXReader();
		Document doc = reader.read("book.xml");
		Element rootElement = doc.getRootElement();
		//凭空创建
		Element Telement = DocumentHelper.createElement("特价");
		Telement.setText("20.0元");
		//挂载
		rootElement.element("书").add(Telement);
		XMLWriter writer = new XMLWriter(new FileOutputStream("book.xml"),OutputFormat.createPrettyPrint());
		writer.write(doc);
		writer.close();
	}
	@Test
	public void delete()throws Exception{
		SAXReader reader=new SAXReader();
		Document doc = reader.read("book.xml");
		Element rootElement = doc.getRootElement();
		Element element = rootElement.element("书").element("特价");
		element.getParent().remove(element);
		XMLWriter writer = new XMLWriter(new FileOutputStream("book.xml"),OutputFormat.createPrettyPrint());
		writer.write(doc);
		writer.close();
	}
	@Test
	public void update() throws Exception{
		//dom4j解析器
		SAXReader reader=new SAXReader();
		//得到document
		Document doc = reader.read("book.xml");
		//得到根元素
		Element rootElement = doc.getRootElement();
		List<Element> elements = rootElement.elements();
		Element element = elements.get(0);
		element.element("售价").setText("50.00元");
		
		
		XMLWriter writer = new XMLWriter(new FileOutputStream("book.xml"),OutputFormat.createPrettyPrint());
		writer.write(doc);
		writer.close();
		
	}
	@Test
	public void find() throws Exception{
		//dom4j解析器
		SAXReader reader=new SAXReader();
		//得到document
		Document doc = reader.read("book.xml");
		//得到根元素
		Element rootElement = doc.getRootElement();
		List<Element> elements = rootElement.elements();
		Element element = elements.get(1);
		System.out.println(element.element("书名").getText());
		
		
	}
}