详解Java解析XML的四种方法

你的名字 2022-06-18 00:13 182阅读 0赞

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。

AD：

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:

<table> 
 <tbody> 
  <tr> 
   <td> <pre>&lt;?xml version="1.0" encoding="UTF-8"?&gt; 
&lt;employees&gt; 
&lt;employee&gt; 
&lt;name&gt;ddviplinux&lt;/name&gt; 
&lt;sex&gt;m&lt;/sex&gt; 
&lt;age&gt;30&lt;/age&gt; 
&lt;/employee&gt; 
&lt;/employees&gt;</pre> </td> 
  </tr> 
 </tbody> 
</table>

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> 
 <tbody> 
  <tr> 
   <td> <pre>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
            
             Element employee=(Element)employeeList.get(i);   
    List employeeInfo=employee.getChildren();   
    for(int j=0;j
             
              System.out.println(((Element)employeeInfo.get(j)).getName()+":"+((Element)employeeInfo.get(j)).getValue());   
    
    }   
    }   
    } catch (JDOMException e) {   
    
    e.printStackTrace();   
    } catch (IOException e) {   
    
    e.printStackTrace();   
    }    
    
    }   
    }