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,平台的无关性使得很多场合都需要用到XML。本文将详细介绍用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();   }    }   }    

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