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)。

　　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。

/**   
 * 定义XML文档建立与解析的接口  
 */  
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 com.alisoft.facepay.framework.bean;

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.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 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) {
			System.out.println(e.getMessage());
		}
	}

	public void createXml(String fileName) {
		Element root = this.document.createElement("employees");
		this.document.appendChild(root);
		Element employee = this.document.createElement("employee");
		Element name = this.document.createElement("name");
		name.appendChild(this.document.createTextNode("丁宏亮"));
		employee.appendChild(name);
		Element sex = this.document.createElement("sex");
		sex.appendChild(this.document.createTextNode("m"));
		employee.appendChild(sex);
		Element age = this.document.createElement("age");
		age.appendChild(this.document.createTextNode("30"));
		employee.appendChild(age);
		root.appendChild(employee);
		TransformerFactory tf = TransformerFactory.newInstance();
		try {
			Transformer transformer = tf.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) {
			System.out.println(e.getMessage());
		} catch (IllegalArgumentException e) {
			System.out.println(e.getMessage());
		} catch (FileNotFoundException e) {
			System.out.println(e.getMessage());
		} catch (TransformerException e) {
			System.out.println(e.getMessage());
		}
	}

	public void parserXml(String fileName) {
		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 (FileNotFoundException e) {
			System.out.println(e.getMessage());
		} catch (ParserConfigurationException e) {
			System.out.println(e.getMessage());
		} catch (SAXException e) {
			System.out.println(e.getMessage());
		} catch (IOException e) {
			System.out.println(e.getMessage());
		}
	}
}

　　 

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

import java.io.FileInputStream;   
import java.io.FileNotFoundException;   
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.xml.sax.Attributes;   
import org.xml.sax.SAXException;   
import org.xml.sax.helpers.DefaultHandler;   
 
public class SaxDemo implements XmlDocument {   
	public void createXml(String fileName) {   
		System.out.println("<<"+filename+">>");   
	}   
	public void parserXml(String fileName) {   
		SAXParserFactory saxfac = SAXParserFactory.newInstance();   
		try {   
			SAXParser saxparser = saxfac.newSAXParser();   
			InputStream is = new FileInputStream(fileName);   
			saxparser.parse(is, new MySAXHandler());   
		} catch (ParserConfigurationException e) {   
			e.printStackTrace();   
		} catch (SAXException e) {   
			e.printStackTrace();   
		} catch (FileNotFoundException e) {   
			e.printStackTrace();   
		} catch (IOException e) {   
			e.printStackTrace();   
		}   
	}   
}   
public 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));   
	}   
}  

import java.io.FileInputStream; 
import java.io.FileNotFoundException; 
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.xml.sax.Attributes; 
import org.xml.sax.SAXException; 
import org.xml.sax.helpers.DefaultHandler; 

public class SaxDemo implements XmlDocument { 
	public void createXml(String fileName) { 
		System.out.println("<<"+filename+">>"); 
	} 
	public void parserXml(String fileName) { 
		SAXParserFactory saxfac = SAXParserFactory.newInstance(); 
		try { 
			SAXParser saxparser = saxfac.newSAXParser(); 
			InputStream is = new FileInputStream(fileName); 
			saxparser.parse(is, new MySAXHandler()); 
		} catch (ParserConfigurationException e) { 
			e.printStackTrace(); 
		} catch (SAXException e) { 
			e.printStackTrace(); 
		} catch (FileNotFoundException e) { 
			e.printStackTrace(); 
		} catch (IOException e) { 
			e.printStackTrace(); 
		} 
	} 
} 
public 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

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

/** * * @author hongliang.dinghl * Dom4j 生成XML文档与解析XML文档 */
public class Dom4jDemo implements XmlDocument {
	public void createXml(String fileName) {
		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("m");
		Element age = employee.addElement("age");
		age.setText("29");
		try {
			Writer fileWriter = new FileWriter(fileName);
			XMLWriter xmlWriter = new XMLWriter(fileWriter);
			xmlWriter.write(document);
			xmlWriter.close();
		} catch (IOException e) {
			System.out.println(e.getMessage());
		}
	}

	public void parserXml(String fileName) {
		File inputXml = new File(fileName);
		SAXReader saxReader = new SAXReader();
		try {
			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 (DocumentException e) {
			System.out.println(e.getMessage());
		}
		System.out.println("dom4j parserXml");
	}
}

　　 

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。

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.List;
import org.jdom.Document;
import org.jdom.Element;
import org.jdom.JDOMException;
import org.jdom.input.SAXBuilder;
import org.jdom.output.XMLOutputter;

public class JDomDemo implements XmlDocument {
	public void createXml(String fileName) {
		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();
		}
	}

	public void parserXml(String fileName) {
		SAXBuilder builder = new SAXBuilder(false);
		try {
			Document document = builder.build(fileName);
			Element employees = document.getRootElement();
			List employeeList = employees.getChildren("employee");
			for (int i = 0; i < employeeList.size(); i++) {
				Element employee = (Element) employeeList.get(i);
				List employeeInfo = employee.getChildren();
				for (int j = 0; j < employeeInfo.size(); j++) {
					System.out.println(((Element) employeeInfo.get(j))
							.getName()
							+ ":" + ((Element) employeeInfo.get(j)).getValue());
				}
			}
		} catch (JDOMException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}