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。

/** 
* 
* @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 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));   
 
}   
 
}  
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, 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。

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;   
/**  
*  
* @author hongliang.dinghl  
* JDOM 生成与解析XML文档  
*  
*/  
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;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();   
}   
 
}   
}   

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