XML.使用java读取xml文件的四种方式

http://blog.sina.com.cn/s/blog_623b41370100g3dk.html

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:

        
        
         
          
           
           <?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; 
 
public interface XmlDocument { 
 
public void createXml(String fileName); 
 
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）。

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; 
 
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 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; 
 
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,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 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 length) 
throws SAXException { 
System.out.println(new String(ch,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; 
 
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;<wbr><wbr> 
 
import java.io.FileNotFoundException;<wbr><wbr> 
import java.io.FileOutputStream;<wbr><wbr> 
import java.io.IOException;<wbr><wbr> 
import java.util.List;<wbr><wbr> 
 
import org.jdom.Document;<wbr><wbr> 
import org.jdom.Element;<wbr><wbr> 
import org.jdom.JDOMException;<wbr><wbr> 
import org.jdom.input.SAXBuilder;<wbr><wbr> 
import org.jdom.output.XMLOutputter;<wbr><wbr> 
 
public class JDomDemo implements XmlDocument {<wbr><wbr> 
 
public void createXml(String fileName) {<wbr><wbr> 
Document document;<wbr><wbr> 
Element root;<wbr><wbr> 
root=new Element("employees");<wbr><wbr> 
document=new Document(root);<wbr><wbr> 
Element employee=new Element("employee");<wbr><wbr> 
root.addContent(employee);<wbr><wbr> 
Element name=new Element("name");<wbr><wbr> 
name.setText("ddvip");<wbr><wbr> 
employee.addContent(name);<wbr><wbr> 
Element sex=new Element("sex");<wbr><wbr> 
sex.setText("m");<wbr><wbr> 
employee.addContent(sex);<wbr><wbr> 
Element age=new Element("age");<wbr><wbr> 
age.setText("23");<wbr><wbr> 
employee.addContent(age);<wbr><wbr> 
XMLOutputter XMLOut = new XMLOutputter();<wbr><wbr> 
try {<wbr><wbr> 
XMLOut.output(document,new FileOutputStream(fileName));<wbr><wbr> 
} catch (FileNotFoundException e) {<wbr><wbr> 
e.printStackTrace();<wbr><wbr> 
} catch (IOException e) {<wbr><wbr> 
e.printStackTrace();<wbr><wbr> 
}<wbr><wbr> 
 
}<wbr><wbr> 
 
public void parserXml(String fileName) {<wbr><wbr> 
SAXBuilder builder=new SAXBuilder(false);<wbr><wbr><wbr> 
try {<wbr><wbr> 
Document document=builder.build(fileName);<wbr><wbr> 
Element employees=document.getRootElement();<wbr><wbr><wbr> 
List employeeList=employees.getChildren("employee");<wbr><wbr> 
for(int i=0;iElement employee=(Element)employeeList.get(i);<wbr><wbr> 
List employeeInfo=employee.getChildren();<wbr><wbr> 
for(int j=0;jSystem.out.println(((Element)employeeInfo.get(j)).getName()+":"+((Element)employeeInfo.get(j)).getValue());<wbr><wbr> 
 
}<wbr><wbr> 
}<wbr><wbr> 
} catch (JDOMException e) {<wbr><wbr> 
 
e.printStackTrace();<wbr><wbr> 
} catch (IOException e) {<wbr><wbr> 
 
e.printStackTrace();<wbr><wbr> 
}<wbr><wbr><wbr> 
 
}<wbr><wbr> 
}<wbr><wbr> 
 
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原文链接：https://www.f2er.com/xml/297961.html

XML.使用java读取xml文件的四种方式

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