访问数据源时出现以下错误？

[lvsevens]

配置context.xml

<Resource name="jdbc/news" auth="Container" type="javax.sql.DataSource" maxActive="100" maxIdle="30" maxWait="10000" username="city" password="sa" driverClassName="oracle.jdbc.driver.OracleDriver" url="jdbc:oracle:thin:@localhost:1521:orcl" />

配置web.xml

<resource-ref>
  	<description>book</description>
  	<res-ref-name>jdbc/news</res-ref-name>
  	<res-type>javax.sql.DataSource</res-type>
  	<res-auth>Container</res-auth>	
  </resource-ref>

测试

package org.example.test;

import java.sql.Connection;
import java.sql.SQLException;


import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.sql.DataSource;


public class Test{
	public static void main(String[] agrs){
			try {
				Context	ctx = new InitialContext();
				DataSource ds=(DataSource)ctx.lookup("java:comp/env/jdbc/news");
				Connection con=ds.getConnection();
				System.out.println("连接成功");
			} catch (NamingException e) {
				e.printStackTrace();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		
	}
}

报的错误是

javax.naming.NoInitialContextException: Need to specify class name in environment or system property, or as an applet parameter, or in an application resource file:  java.naming.factory.initial
	at javax.naming.spi.NamingManager.getInitialContext(NamingManager.java:645)
	at javax.naming.InitialContext.getDefaultInitCtx(InitialContext.java:288)
	at javax.naming.InitialContext.getURLOrDefaultInitCtx(InitialContext.java:325)
	at javax.naming.InitialContext.lookup(InitialContext.java:392)
	at org.example.test.Test.main(Test.java:17)