Java学习之道：详解Java解析XML的四种方法

ゞ浴缸里的玫瑰 2021-09-10 09:04 342阅读 0赞

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:

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。

<table style="color:rgb(51,51,51); font-family:宋体; font-size:14px; line-height:28px; background-color:rgb(248,248,248)"> 
 <tbody> 
 <tr> 
 <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px"> <pre style="margin-top:0px; margin-bottom:1em; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; font-family:'Courier New',monospace; width:392px; overflow-x:auto; overflow-y:auto; background-color:rgb(230,230,230)">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); } </pre> </td> 
 </tr> 
 </tbody> 
</table>

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;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();   }    }   }