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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。

作者:cnlw1985来源:javaeye|2009-03-31 13:12

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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();  
}   

}  
}  
 

【编辑推荐】

  1. XML新手入门 创建构造良好的XML
  2. 实现XML和Web服务时要避免的三种常见错误
  3. 数据库中的pureXML优点介绍
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