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。

/** 
* 
* @author hongliang.dinghl 
* 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）。

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; 
/** 
* 
* @author hongliang.dinghl 
* DOM生成与解析XML文档 
*/ 
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；

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;   
/**  
*   
* @author hongliang.dinghl  
* SAX文档解析  
*/  
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();   

}   

}   

}   

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 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,length));   

}   

}  
package com.alisoft.facepay.framework.bean; 
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; 
/** 
* 
* @author hongliang.dinghl 
* SAX文档解析 
*/ 
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(); 
} 
} 
} 
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,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 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 length) 
throws SAXException { 
System.out.println(new String(ch,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。

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。