解析XML文件

解析xml文件：
  1，dom
   dom是用于平台和语言无关的方式表示xml文档的W3C标准，把xml文档转化成一个包含其内容的树，并可以对树进行遍历。
   DocumentBuilderFactory factory=DocumentBuilderFactory.newInstance();
   DocumentBuilder builder=factory.newDocumentBuilder();
   读：
    Document doc=builder.parse(File file);
    NodeList nl=doc.getElementByTagName("NodeName");
    for(int i=0;i<nl.getLength();i++){
     doc.getElementByTagName("childNodeName").item(i).getFirstChild().getNodeValue();
     doc.getElementByTagName("childNodeName").item(i).getFirstChild().getNodeValue();
    }
   写:
    Document doc=builder.parse(File file);//如果是要创建新的xml:Document doc=builder.newDocument();
    Element root=doc.getDocumentElement("rootName");  //得到跟节点
    Element childNode=doc.createElement("childNodeName");  //创建一个子节点
    childNode.setAttribute("name","id");     //设置属性
    childNode.setTextContent("value");    //设置内容
    doc.appendChild(root);
    root.appendChild(childNode);
    TranformerFactory factory=TranformerFactory.newInstance();
    Tranformer tranformer=factory.newTranformer();
    tranformer.tranformer(new Resource(doc),new StreanResult(new File("demo.xml")))

package dom;
import java.io.File;
/**
 * 使用dom解析xml文件：DecumentBuilderFactory dbf=DecumentBuilderFactory.newInstace()
 *                     DecumentBuilder db=dbf.newDocumentBuilder()
 *                     Document d=db.parse(new File(path))
 *                     NodeList
 */

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.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;
public class DomXml {
    public static void main(String[] args) {
        writeXml();
        readXml();
    }
    public static void readXml(){
        try{
            File file=new File("demo.xml");
            DocumentBuilderFactory     dbf=DocumentBuilderFactory.newInstance();
            DocumentBuilder db=dbf.newDocumentBuilder();
            Document doc=db.parse(file);
            NodeList nl=doc.getElementsByTagName("info");
            for(int i=0;i<nl.getLength();i++){
                System.out.println("name="+doc.getElementsByTagName("name").item(i).getFirstChild().getNodeValue());
                System.out.println("password="+doc.getElementsByTagName("password").item(i).getFirstChild().getNodeValue());
            }
        }catch(Exception e){
            e.printStackTrace();
        }
    }
    public static void writeXml(){
        try{
            File file=new File("demo.xml");
            DocumentBuilderFactory dbf=DocumentBuilderFactory.newInstance();
            DocumentBuilder db=dbf.newDocumentBuilder();
//            Document doc=db.newDocument();
            Document doc=db.parse(file);
            Element root=doc.getDocumentElement();
            Element info=doc.createElement("info");
            Element info1=doc.createElement("info");
            info.setAttribute("name", "admin2");
            info.setAttribute("id", "2");
            info.setTextContent("ddd=dasd");
            info1.setAttribute("name", "admin2");
            info1.setAttribute("id", "2");
            info1.setTextContent("ddd=dasd");
            root.appendChild(info);
            root.appendChild(info1);
            TransformerFactory factory = TransformerFactory.newInstance();
            Transformer former = factory.newTransformer();
            former.transform(new DOMSource(doc), new StreamResult(new File("demo.xml")));

            
        }catch(Exception e){
            e.printStackTrace();
        }
    }
}

  2，SAX
    不需要将数据存储在内存中，不必解析整个文档，满足条件即可截至解析。采用事件模型
    SAXParserFactory factory=SAXParserFactory.newInstance();
    SAXParser saxparser = factory.newSAXParser();
    SaxHandler handler = new SaxHandler();
    saxparser.parse("dom.xml",handler);

    class SaxHandler extends DefaultHandler{
     startDecument(); //开始解析
     endDecument(); //结束解析
     startElement(url,localName,qName,attribute){
      if("childNodeName".equals(qName)){
       print("属性："+attribute.getQName);
       print("值："+attribute.getValue);
      }
     }
     endElement(url,localName,qName,attribute){}
     characters(char[],int,length){
      String NodeValue=new String(char,start,length);
      print(NodeValue);
     }
    }

package dom;

import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.DefaultHandler;

class SaxHandler extends DefaultHandler{
    @Override
    public void startDocument() throws SAXException {
        // TODO Auto-generated method stub
        super.startDocument();
        System.out.println("-------------解析开始----------------");
    }
    @Override
    public void endDocument() throws SAXException {
        // TODO Auto-generated method stub
        super.endDocument();
        System.out.println("------------解析结束------------------");
    }
    @Override
    public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
        // TODO Auto-generated method stub
        super.startElement(uri, localName, qName, attributes);
        if(qName.equals("info")){
            int length=attributes.getLength();
            for(int i=0;i<length;i++){
                System.out.print("属性："+attributes.getQName(i));
                System.out.println("值："+attributes.getValue(i));
            }
        }else{
            System.out.println("节点："+qName);
        }
    }
    @Override
    public void endElement(String uri, String localName, String qName) throws SAXException {
        // TODO Auto-generated method stub
        super.endElement(uri, localName, qName);
    }
    @Override
    public void characters(char[] ch, int start, int length) throws SAXException {
        // TODO Auto-generated method stub
        super.characters(ch, start, length);
        String flag=new String(ch,start,length);
        if(!("".equals(flag.trim()))){
            System.out.println("节点值为："+flag);
        }
        System.out.println();
    }
    
}
public class SaxXml {
    public static void main(String[] args) {
    try{
        SAXParserFactory factory=SAXParserFactory.newInstance();   //创建解析工厂
        SAXParser saxParser=factory.newSAXParser();                //创建解析器
        SaxHandler handler=new SaxHandler();
        saxParser.parse("demo.xml", handler);
    }catch(Exception e){
        e.printStackTrace();
    }
    }
}

  3，JDOM
   目的成为java特定文档模型，简化与XML的交互并且比使用DOM更快
  4，DOM4J