更改jdk的默认xml解析器

在命令行下运行java程序;

设置classpath=.;E:\normal\dev\j2ee\xml\xerces\xerces-2_9_1\xercesImpl.jar

(或E:\normal\dev\j2ee\xml\xerces\xerces-2_9_1\xercesImpl.jar;.)

执行:

javac DOMStudentsInfo.java

java DOMStudentsInfo

无论是否存在jaxp.properties文件都可运行,

jaxp.properties内容为:

javax.xml.parsers.DocumentBuilderFactory=org.apache.xerces.jaxp.DocumentBuilderFactoryImpl

javax.xml.parsers.SAXParserFactory=org.apache.xerces.jaxp.SAXParserFactoryImpl

运行结果为:

E:\MyDoc\dev\Temp Pro\eclipse\lesson3\src>java DOMStudentsInfo

JAXP: find factoryId =javax.xml.parsers.DocumentBuilderFactory

JAXP: found jar resource=META-INF/services/javax.xml.parsers.Document

uilderFactory using ClassLoader: sun.misc.Launcher$AppClassLoader@198

1f

JAXP: found in resource, value=org.apache.xerces.jaxp.DocumentBuilder

actoryImpl

JAXP: created new instance of class org.apache.xerces.jaxp.DocumentBu

lderFactoryImpl using ClassLoader: sun.misc.Launcher$AppClassLoader@1

821f

DocumentBuilderFactory: org.apache.xerces.jaxp.DocumentBuilderFactory

mpl

DocumentBuilder: org.apache.xerces.jaxp.DocumentBuilderImpl

Name: 张三

Age: 20

---------------

Name: 李四

Age: 21

---------------

ps:

1. 修改环境变量后必需重新打开cmd窗口!

2. DOMStudentsInfo.java 内容为:

import java.io.File;

import java.io.IOException;

import javax.xml.parsers.DocumentBuilder;

import javax.xml.parsers.DocumentBuilderFactory;

import javax.xml.parsers.ParserConfigurationException;

import org.w3c.dom.*;

import org.xml.sax.SAXException;

public class DOMStudentsInfo {

public static void main(String[] args) {

System.setProperty("jaxp.debug","TRUE");

DocumentBuilderFactory dbf =DocumentBuilderFactory.newInstance();

System.out.println("DocumentBuilderFactory: "+dbf.getClass().getName());

try {

DocumentBuilder db =dbf.newDocumentBuilder();

System.out.println("DocumentBuilder: "+db.getClass().getName());

Document doc =db.parse(new File("Students.xml"));

NodeList nl =doc.getElementsByTagName_r("student");

int len =nl.getLength();

for(int i=0;i<len;i++)

{

   Element ele =(Element) nl.item(i);

   Node ndName =ele.getElementsByTagName_r("name").item(0);

   Node ndAge =ele.getElementsByTagName_r("age").item(0);

   

   String strName =ndName.getFirstChild().getNodue();

   String strAge =ndAge.getFirstChild().getNodue();

   

   System.out.println("Name: "+strName);

   System.out.println("Age: "+strAge);

   System.out.println("---------------");

}

}

catch (ParserConfigurationException e) {

// TODO Auto-generated catch block

e.printStackTrace();

} catch (SAXException e)

{

   // TODO Auto-generated catch block

   e.printStackTrace();

} catch (IOException e)

{

   // TODO Auto-generated catch block

   e.printStackTrace();

}

}

}

3.然而在eclipse3.5.1下，不管是否正存在jaxp.properties以及是否设置了classpath=E:\normal\dev\j2ee\xml\xerces\xerces-2_9_1\xercesImpl.jar;. eclipse运行结果都为:

JAXP: find factoryId =javax.xml.parsers.DocumentBuilderFactory

JAXP: loaded from fallback value: com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderFactoryImpl

JAXP: created new instance of class com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderFactoryImpl using ClassLoader: null

DocumentBuilderFactory: com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderFactoryImpl

DocumentBuilder: com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl

Name: 张三

Age: 20

---------------

Name: 李四

Age: 21

---------------

但是,当eclipse导入了xercesImpl.jar,则总是输出:

JAXP: find factoryId =javax.xml.parsers.DocumentBuilderFactory

JAXP: found jar resource=META-INF/services/javax.xml.parsers.DocumentBuilderFactory using ClassLoader: sun.misc.Launcher$AppClassLoader@19821f

JAXP: found in resource, value=org.apache.xerces.jaxp.DocumentBuilderFactoryImpl

JAXP: created new instance of class org.apache.xerces.jaxp.DocumentBuilderFactoryImpl using ClassLoader: sun.misc.Launcher$AppClassLoader@19821f

DocumentBuilderFactory: org.apache.xerces.jaxp.DocumentBuilderFactoryImpl

DocumentBuilder: org.apache.xerces.jaxp.DocumentBuilderImpl

Name: 张三

Age: 20

---------------

Name: 李四

Age: 21

---------------

-----------------------------------------------------

总结:

1. 使用eclipse时若需替换jdk默认的xml解析器,则中需要导入相应的工厂实现。

2. 使用命令行执行java程序时,要在环境变量下包含工厂实现文件的绝对路径。