XML作用：不同应用之间的通信和数据共享

Dom遍历法：对内存消耗大，容易内存溢出

SAX方法：事件驱动模式，缺点 不易操作，很难同时访问多处不同数据，对内存消耗不大，速度快

jdom方法：

dom4j方法：优秀比jdom优秀

Dom遍历法：全部加载内容到内存

DocumentBuilderFactory d=DocumentBuilderFactory.newInstance();

		try {

			DocumentBuilder bu=d.newDocumentBuilder();

			Document dom=bu.parse("pom.xml");

			NodeList nl=dom.getElementsByTagName("dependency");

			System.out.println(nl.getLength());

			for(int i=0;i<nl.getLength();i++) {

				Node node=nl.item(i);

				NodeList nnm=node.getChildNodes();

				for(int k=0;k<nnm.getLength();k++) {

					Node node1=nnm.item(k);

					if(node1.getNodeType()==Node.ELEMENT_NODE) {

						String tt=node1.getNodeName();

						String tt1=node1.getTextContent();

						System.out.println(tt+":"+tt1+"\n");

					}

				}

			}

		} catch (ParserConfigurationException e) {

			// TODO Auto-generated catch block

			e.printStackTrace();

		} catch (SAXException e) {

			// TODO Auto-generated catch block

			e.printStackTrace();

		} catch (IOException e) {

			// TODO Auto-generated catch block

			e.printStackTrace();

		}

	}

SAX方法 两个步骤：

package com.xml;

import org.xml.sax.Attributes;

import org.xml.sax.SAXException;

import org.xml.sax.helpers.DefaultHandler;

public class SAXhandler extends DefaultHandler {

	int index=0;

	public void startElement(String uri, String localName,String qName,Attributes attributes) throws SAXException {

		super.startElement(uri, localName, qName, attributes);

		if(qName=="project") {

			index++;

			System.out.println("开始遍历第"+index+"gejiedian");

			//String va=attributes.getValue("id");//已知属性名称

			int aa=attributes.getLength();

			for(int i=0;i<aa;i++) {

				String name=attributes.getQName(i);

				String va=attributes.getValue(name);

				System.out.println(name+":"+va);

			}

		}else if(qName.equals("dependency")) {

			System.out.print("节点名称："+qName);

		}

	}

	public void endElement(String uri, String localName, String qName) throws SAXException {

		super.endElement(uri, localName, qName);

		if(qName.equals("project")) {

			System.out.println("end遍历第"+index+"gejiedian");

		}

	}

	public void startDocument() throws SAXException {

		super.startDocument();

		System.out.println("解析开始");

	}

	public void endDocument() throws SAXException {

		super.endDocument();

		System.out.println("解析结束");

	}

	public void characters(char[]ch, int start, int length) throws SAXException {

		super.characters(ch, start, length);

		String value=new String(ch, start, length);

		if(!value.trim().equals("")) {

			System.out.println(value);

		}

	}

}

import java.io.IOException;

import javax.xml.parsers.ParserConfigurationException;

import javax.xml.parsers.SAXParser;

import javax.xml.parsers.SAXParserFactory;

import org.xml.sax.SAXException;

public class SAX {

	public static void main(String[] args) {

		// TODO Auto-generated method stub

		SAXParserFactory sf=SAXParserFactory.newInstance();

		try {

			SAXParser sp=sf.newSAXParser();

			SAXhandler sh=new SAXhandler();

			sp.parse("pom.xml", sh);

		} catch (ParserConfigurationException | SAXException e) {

			// TODO Auto-generated catch block

			e.printStackTrace();

		} catch (IOException e) {

			// TODO Auto-generated catch block

			e.printStackTrace();

		}

	}

}

jdom方法：需要额外jar包

import java.io.File;

import java.io.IOException;

import java.util.ArrayList;

import java.util.List;

import org.jdom.Attribute;

import org.jdom.Document;

import org.jdom.Element;

import org.jdom.JDOMException;

import org.jdom.input.SAXBuilder;

public class JDOM {

	public static void main(String[] args) throws JDOMException, IOException {

		SAXBuilder sb=new SAXBuilder();

		Document Document = sb.build(new File("pom1.xml"));

		Element rootelement=Document.getRootElement();

		List<Element> listele=rootelement.getChildren();

		List<Object> lo=new ArrayList<Object>();

		for( Element ele:listele) {

			obj o=new obj();

			System.out.println("开始"+(listele.indexOf(ele)+1)+"个");

			List<Attribute> attrs=ele.getAttributes();

			for(Attribute attr:attrs) {

				String attrname=attr.getName();

				String attrvalue=attr.getValue();

				System.out.println(attrname+":"+attrvalue);

			}

			List<Element> list_sun= ele.getChildren();

			for( Element ele1:list_sun) {

				if(ele1.getName().equals("groupId") ) {

				o.setGroupId(ele1.getValue());

			}else if(ele1.getName().equals("artifactId")) {

				o.setArtifactId(ele1.getValue());

			}

				}

			lo.add(o);

			o=null;

		}

		System.out.println(lo);

	}

}

dom4j方法：

import java.io.File;

import java.util.Iterator;

import java.util.List;

import org.dom4j.Attribute;

import org.dom4j.Document;

import org.dom4j.DocumentException;

import org.dom4j.Element;

import org.dom4j.io.SAXReader;

public class dom4j {

	public static void main(String[] args) throws DocumentException {

		SAXReader sr=new SAXReader();

		Document Document = sr.read(new File("pom1.xml"));

		Element root=Document.getRootElement();

		Iterator it=root.elementIterator();

		while(it.hasNext()) {

			Element ele=(Element) it.next();

			List<Attribute> list=ele.attributes();

			for(Attribute attr:list) {

			System.out.println(attr.getName()+":"+attr.getValue());

			}

			Iterator  suneles=ele.elementIterator();

			while(suneles.hasNext()) {

				Element ele1=(Element) suneles.next();

				System.out.println(ele1.getName()+":"+ele1.getStringValue());

				}

		}

	}

}