详解Java解析XML的四种方法

XML现在已经成为一种通用的数据交换格式,它的平台无关性,语言无关性,系统无关性,给数据集成与交互带来了极大的方便。对于XML本身的语法知识与技术细节,需要阅读相关的技术文献,这里面包括的内容有DOM(Document Object Model),DTD(Document Type Definition),SAX(Simple API for XML),XSD(Xml Schema Definition),XSLT(Extensible Stylesheet Language Transformations),具体可参阅w3c官方网站文档http://www.w3.org获取更多信息。

XML在不同的语言里解析方式都是一样的,只不过实现的语法不同而已。基本的解析方式有两种,一种叫SAX，另一种叫DOM。SAX是基于事件流的解析,DOM是基于XML文档树结构的解析。假设我们XML的内容和结构如下: 

<?xml version="1.0" encoding="UTF-8"?> 
<employees> 
<employee> 
<name>ddviplinux</name> 
<sex>m</sex> 
<age>30</age> 
</employee> 
</employees>

　　本文使用JAVA语言来实现DOM与SAX的XML文档生成与解析。 
首先定义一个操作XML文档的接口XmlDocument 它定义了XML文档的建立与解析的接口。

package org.hxwl.axis.service;
/**
* SAX是基于事件流的解析,DOM是基于XML文档树结构的解析
* @author ZENGSONG
*
*/
public interface XmlDocument {
/**
* 建立XML文档
* @param fileName 文件全路径名称
*/
public void createXml(String fileName);
/**
* 解析XML文档
* @param fileName 文件全路径名称
*/
public void parserXml(String fileName);
}

　　

1.DOM生成和解析XML文档

为 XML 文档的已解析版本定义了一组接口。解析器读入整个文档，然后构建一个驻留内存的树结构，然后代码就可以使用 DOM 接口来操作这个树结构。优点：整个文档树在内存中，便于操作；支持删除、修改、重新排列等多种功能；缺点：将整个文档调入内存（包括无用的节点），浪费时间和空间；使用场合：一旦解析了文档还需多次访问这些数据；硬件资源充足（内存、CPU）。 

package org.hxwl.axis.service.impl;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.hxwl.axis.service.XmlDocument;
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;
/**
* DOM生成与解析XML文档
* @author ZENGSONG
*
*/
public class DomDemo implements XmlDocument {
private Document document;
private String fileName;

public void init() {
try {
DocumentBuilderFactory factory = DocumentBuilderFactory
.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
this.document = builder.newDocument();

} catch (ParserConfigurationException e) {
// TODO Auto-generated catch block
System.out.println(e.getMessage());
}
}

@Override
public void createXml(String fileName) {
// TODO Auto-generated method stub
Element root = this.document.createElement("employee");
this.document.appendChild(root);
Element employee = this.document.createElement("employee");
Element name = this.document.createElement("name");
name.appendChild(this.document.createTextNode("郭靖"));
employee.appendChild(name);
Element sex = this.document.createElement("sex");
sex.appendChild(this.document.createTextNode("男"));
employee.appendChild(sex);
Element age = this.document.createElement("age");
age.appendChild(this.document.createTextNode("30"));
employee.appendChild(age);

root.appendChild(employee);

TransformerFactory tFactory = TransformerFactory.newInstance();
try {
Transformer transformer = tFactory.newTransformer();
DOMSource source = new DOMSource(document);
transformer.setOutputProperty(OutputKeys.ENCODING, "gb2312");
transformer.setOutputProperty(OutputKeys.INDENT, "yes");
PrintWriter pw = new PrintWriter(new FileOutputStream(fileName));
StreamResult result = new StreamResult(pw);
transformer.transform(source, result);
System.out.println("生成XML文件成功!");

} catch (TransformerConfigurationException e) {
// TODO Auto-generated catch blockk
e.printStackTrace();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (TransformerException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}

@Override
public void parserXml(String fileName) {
// TODO Auto-generated method stub
try {
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
Document document = db.parse(fileName);
NodeList employees = document.getChildNodes();
for (int i = 0; i < employees.getLength(); i++) {
Node employee = employees.item(i);
NodeList employeeInfo = employee.getChildNodes();
for (int j = 0; j < employeeInfo.getLength(); j++) {
Node node = employeeInfo.item(j);
NodeList employeeMeta = node.getChildNodes();
for (int k = 0; k < employeeMeta.getLength(); k++) {
System.out.println(employeeMeta.item(k).getNodeName()
+ ":" + employeeMeta.item(k).getTextContent());
}
}
}
System.out.println("解析完毕!");
} catch (SAXException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (ParserConfigurationException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}

　　

2.SAX生成和解析XML文档

为解决DOM的问题，出现了SAX。SAX ，事件驱动。当解析器发现元素开始、元素结束、文本、文档的开始或结束等时，发送事件，程序员编写响应这些事件的代码，保存数据。优点：不用事先调入整个文档，占用资源少；SAX解析器代码比DOM解析器代码小，适于Applet，下载。缺点：不是持久的；事件过后，若没保存数据，那么数据就丢了；无状态性；从事件中只能得到文本，但不知该文本属于哪个元素；使用场合：Applet;只需XML文档的少量内容，很少回头访问；机器内存少；

Java代码

package org.hxwl.axis.service.impl;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;

import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.hxwl.axis.service.XmlDocument;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;
/**
 * SAX文档解析
 * @author ZENGSONG
 *
 */
public class SaxDemo implements XmlDocument {

	@Override
	public void createXml(String fileName) {
		// TODO Auto-generated method stub
		System.out.println("<<" + fileName + ">>");
	}

	@Override
	public void parserXml(String fileName) {
		// TODO Auto-generated method stub
		try {
			SAXParserFactory saxfac = SAXParserFactory.newInstance();
			SAXParser saxparser = saxfac.newSAXParser();
			InputStream is = new FileInputStream(fileName);

			saxparser.parse(is, new MySAXHandler());
		} catch (SAXException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (ParserConfigurationException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

class MySAXHandler extends DefaultHandler {

	boolean hasAttribute = false;

	Attributes attributes = null;

	public void startDocument() throws SAXException {

		System.out.println("文档开始打印了");

	}

	public void endDocument() throws SAXException {

		System.out.println("文档打印结束了");

	}

	public void startElement(String uri, String localName, String qName,
			Attributes attributes) throws SAXException {
		if (qName.equals("employees")) {
			return;
		}
		if (qName.equals("employee")) {
			System.out.println(qName);
		}
		if (attributes.getLength() > 0) {
			this.attributes = attributes;
			this.hasAttribute = true;
		}
	}

	public void endElement(String uri, String localName, String qName)
			throws SAXException {
		if (hasAttribute && (attributes != null)) {
			for (int i = 0; i < attributes.getLength(); i++) {
				System.out.println(attributes.getQName(0)
						+ attributes.getValue(0));
			}
		}
	}

	public void characters(char[] ch, int start, int length)
			throws SAXException {
		System.out.println(new String(ch, start, length));
	}
}

　　

3.DOM4J生成和解析XML文档

DOM4J 是一个非常非常优秀的Java XML API，具有性能优异、功能强大和极端易用使用的特点，同时它也是一个开放源代码的软件。如今你可以看到越来越多的 Java 软件都在使用 DOM4J 来读写 XML，特别值得一提的是连 Sun 的 JAXM 也在用 DOM4J。

Java代码

package org.hxwl.axis.service.impl;

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Writer;
import java.net.MalformedURLException;
import java.util.Iterator;

import org.hxwl.axis.service.XmlDocument;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.DocumentHelper;  
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
import org.dom4j.io.XMLWriter;
/**
 * Dom4j 生成XML文档与解析XML文档 
 * @author ZENGSONG
 *
 */
public class Dom4jDemo implements XmlDocument{

	@Override
	public void createXml(String fileName) {
		// TODO Auto-generated method stub
		Document document=DocumentHelper.createDocument();
		Element employees=document.addElement("employees");
		Element employee=employees.addElement("employee");
		Element name=employee.addElement("name");
		name.setText("ddvip");
		Element sex=employee.addElement("sex");
		sex.setText("男");
		Element age=employee.addElement("age");
		age.setText("30");
		
		Writer fileWriter;
		try {
			fileWriter = new FileWriter(fileName);
			XMLWriter xmlwriter=new XMLWriter(fileWriter);
			xmlwriter.write(document);
			xmlwriter.close();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			System.out.println(e.getMessage());
		}
	}

	@Override
	public void parserXml(String fileName) {
		// TODO Auto-generated method stub
		try {
		File inputXml=new File(fileName);
		SAXReader saxReader=new SAXReader();
		Document document = saxReader.read(inputXml);
		Element employees=document.getRootElement();
		for(Iterator i=employees.elementIterator();i.hasNext();){
			Element employee=(Element)i.next();
			for(Iterator j=employee.elementIterator();j.hasNext();){
				Element node=(Element)j.next();
				System.out.println(node.getName()+":"+node.getText());
			}
		}
		} catch (MalformedURLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (DocumentException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

　　

4.JDOM生成和解析XML  

为减少DOM、SAX的编码量，出现了JDOM；优点：20-80原则，极大减少了代码量。使用场合：要实现的功能简单，如解析、创建等，但在底层，JDOM还是使用SAX（最常用）、DOM、Xanan文档。

java 代码

package org.hxwl.axis.service.impl;

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Iterator;
import java.util.List;

import org.hxwl.axis.service.XmlDocument;
import org.jdom.Document;
import org.jdom.Element;
import org.jdom.JDOMException;
import org.jdom.input.SAXBuilder;
import org.jdom.output.XMLOutputter;

/**
 * JDOM 生成与解析XML文档
 * 
 * @author ZENGSONG
 * 
 */
public class JDomDemo implements XmlDocument {

	@Override
	public void createXml(String fileName) {
		// TODO Auto-generated method stub
		Document document;
		Element root;
		root = new Element("employees");
		document = new Document(root);
		Element employee = new Element("employee");
		root.addContent(employee);
		Element name = new Element("name");
		name.setText("ddvip");
		employee.addContent(name);
		Element sex = new Element("sex");
		sex.setText("m");
		employee.addContent(sex);
		Element age = new Element("age");
		age.setText("23");
		employee.addContent(age);
		XMLOutputter XMLOut = new XMLOutputter();
		try {
			XMLOut.output(document, new FileOutputStream(fileName));
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	@Override
	public void parserXml(String fileName) {
		// TODO Auto-generated method stub
		SAXBuilder builder=new SAXBuilder(false);    
		try {   
		Document document=builder.build(fileName);   
		Element employees=document.getRootElement();    
		List employeeList=employees.getChildren("employee");   
//		Element driverClassNameElement = (Element)XPath.selectSingleNode(employees, "//sys-config/jdbc-info/driver-class-name");
//		String driverClassName = driverClassNameElement.getText();
//		System.out.println("driverClassName = " + driverClassName);
//		
//		List provinceList = XPath.selectNodes(employees, "//sys-config/provinces-info/province");
//		for(Iterator it = provinceList.iterator();it.hasNext();){
//			Element provinceEle = (Element)it.next();
//			String proId = provinceEle.getAttributeValue("id");
//			String proName = provinceEle.getAttributeValue("name");
//
//			System.out.println("provinceId = " + proId + "   provinceName = " + proName);
//			
//			List cityEleList = (List)provinceEle.getChildren("city");
//			
//			for(Iterator cityIt = cityEleList.iterator();cityIt.hasNext();){
//				Element cityEle = (Element)cityIt.next();
//				String cityId = cityEle.getAttributeValue("id");
//				String cityName = cityEle.getText();
//
//				System.out.println("    cityId = " + cityId + "   cityName = " + cityName);
//			}
//		}
//		for(int i=0;iElement employee=(Element)employeeList.get(i);   
//				List employeeInfo=employee.getChildren();   
//				for(int j=0;jSystem.out.println(((Element)employeeInfo.get(j)).getName()+":"+((Element)employeeInfo.get(j)).getValue()); 
						
		} catch (JDOMException e) {   

		e.printStackTrace();   
//		} catch (IOException e) {   
//		e.printStackTrace();   
		}    
	}
}

　　这个JDOM解析还有待研究。

参考自：http://developer.51cto.com/art/200903/117512.htm