Java解析xml文件

读xml文件：

 xml文件内容：

<?xml version="1.0" encoding="UTF-8"?>
<Languages cat="it">
	<lan id="1">
		<name>Java</name>
		<ide>Eclipse</ide>
	</lan>
	<lan id="2">
		<name>Swift</name>
		<ide>Xcode</ide>
	</lan>
	<lan id="3">
		<name>C#</name>
		<ide>Visual Studio</ide>
	</lan>
</Languages>

 代码：

package XMLParse;

import java.io.File;
import java.io.IOException;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

public class ReadXML {

	public static void main(String[] args) {
		try {
				//DOM方式解析xml文件
			
			DocumentBuilderFactory factory=DocumentBuilderFactory.newInstance();
			DocumentBuilder builder=factory.newDocumentBuilder();
			Document document=builder.parse(new File("languages.xml"));
			Element root=document.getDocumentElement();
			System.out.println("categary:"+root.getAttribute("cat"));
			NodeList list=root.getElementsByTagName("lan");
			for (int i = 0; i < list.getLength(); i++) {
				Element lan= (Element) list.item(i);
				System.out.println("*******************");
				System.out.println("id="+lan.getAttribute("id"));
				
				NodeList cList=lan.getChildNodes();	//会将文件里的换行也当成子节点返回到cList中
				for (int j = 0; j < cList.getLength(); j++) {
					Node c= cList.item(j);
					if(c instanceof Element) {	//因为cList中包含了空格和换行，所以需要判断是否是元素
						System.out.println(c.getNodeName()+"="+c.getTextContent());
						
					}
				}
			}
			
			
		} catch (ParserConfigurationException e) {
			e.printStackTrace();
		} catch (SAXException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		
	}

}

 注意：NodeList cList=lan.getChildNodes(); 会把原文件中的换行也当作子节点，所以需要判断：if(c instanceof Element){……}

---

创建xml文件：

import java.io.File;
import java.io.StringWriter;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerException;
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;

public class creaetXML {

	public static void main(String[] args) {
		try {
			
			DocumentBuilderFactory factory=DocumentBuilderFactory.newInstance();
			DocumentBuilder builder=factory.newDocumentBuilder();
			Document document=builder.newDocument();
			
			Element root=document.createElement("Languages");
			root.setAttribute("cat", "IT");
			
			Element lan1=document.createElement("lan");
			lan1.setAttribute("id", "1");
			Element name1=document.createElement("name");
			name1.setTextContent("java");
			Element ide1=document.createElement("ide");
			ide1.setTextContent("eclipse");
			lan1.appendChild(name1);
			lan1.appendChild(ide1);
			root.appendChild(lan1);
			document.appendChild(root);
			
			Element lan2=document.createElement("lan");
			lan2.setAttribute("id", "2");
			Element name2=document.createElement("name");
			name2.setTextContent("c#");
			Element ide2=document.createElement("ide");
			ide2.setTextContent("visual studio");
			lan2.appendChild(name2);
			lan2.appendChild(ide2);
			root.appendChild(lan2);
			
			//*************以下为输出**************
			TransformerFactory transformerFactory=TransformerFactory.newInstance();
			Transformer transformer=transformerFactory.newTransformer();
			StringWriter writer=new StringWriter();
			transformer.transform(new DOMSource(document), new StreamResult(writer));//输出到控制台
			System.out.println(writer.toString());
			
			transformer.transform(new DOMSource(document), new StreamResult(new File("newxml.xml")));
			
			
		} catch (ParserConfigurationException e) {
			e.printStackTrace();
		} catch (TransformerException e) {
			e.printStackTrace();
		}
		
		
	}

}

 其中重点是如何输出：

TransformerFactory transformerFactory=TransformerFactory.newInstance();
Transformer transformer=transformerFactory.newTransformer();
StringWriter writer=new StringWriter();
transformer.transform(new DOMSource(document), new StreamResult(writer));//输出到控制台
System.out.println(writer.toString());
			
transformer.transform(new DOMSource(document), new StreamResult(new File("newxml.xml")));

---

使用第三方库dom4j操作xml数据：

package testDom4j;

import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.DocumentHelper;

public class testDom4j {

	public static void main(String[] args) {
		String xmlString="<root><people>panghu</people></root>";
		try {
			Document document=DocumentHelper.parseText(xmlString);
			System.out.println(document.asXML());
			
		} catch (DocumentException e) {
			e.printStackTrace();
		}
	}

}

 效率高很多。