[转]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 com.alisoft.facepay.framework.bean;
/**
*
* @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）。 

 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;
 /**
 *
 * @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；

Java代码

 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));   

 }   

 }
 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。

Java代码

 package com.alisoft.facepay.framework.bean;
 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。

 package com.alisoft.facepay.framework.bean;   

 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();
 }    

 }
 }
   

原文链接：http://developer.51cto.com/art/200903/117512.htm