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:

ddviplinux

m

30

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(">"); } 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 ");}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; Elementroot; 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(); }} }