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:
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。
/** * * @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.xmlTest;import java.io.File;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;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;/** * ClassName: XmlTest date: 2015年2月28日 上午10:57:42 * * @author limh * @since JDK 1.7 DOM生成与解析XML文档 */public class XmlDomDemoTest implements XmlDocument { private Document document; 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 fileName1) { String fileName = fileName1; //创建File对象，参数为String类型，表示目录名 File myFile = new File(fileName); //判断文件是否存在，如果不存在则调用createNewFile()方法创建新目录，否则跳至异常处理代码 if(!myFile.exists()) try { myFile.createNewFile(); } catch (IOException e1) { e1.printStackTrace(); } 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, "utf-8"); 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()); } } public static void main(String[] args) { String pathname = "/home/zhangmeng/桌面/232323/ccc.xml"; XmlDomDemoTest xmldomdemotest = new XmlDomDemoTest(); xmldomdemotest.init(); //xmldomdemotest.createXml(pathname);//创建xml xmldomdemotest.parserXml(pathname);//解析xml }}
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.xmlTest;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 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.xmlTest;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); //判断文件是否存在，如果不存在则调用createNewFile()方法创建新目录，否则跳至异常处理代码 if(!inputXml.exists()) try { inputXml.createNewFile(); } catch (IOException e1) { e1.printStackTrace(); } 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"); } public static void main(String[] args) { String pathname = "/home/zhangmeng/桌面/232323/a22222.xml"; Dom4jDemo xmldomdemotest = new Dom4jDemo(); //xmldomdemotest.createXml(pathname);//创建xml xmldomdemotest.parserXml(pathname);//解析xml }} 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.xmlTest;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; i < employeeList.size(); i++) { Element employee = (Element) employeeList.get(i); List employeeInfo = employee.getChildren(); for (int j = 0; j < employeeInfo.size(); j++) { System.out.println(((Element) employeeInfo.get(j)) .getName() + ":" + ((Element) employeeInfo.get(j)).getValue()); } } } catch (JDOMException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } }}