DataSource是怎么连接oracle的啊？

有个项目用到到数据源，但是不会用，急盼赐教！
    Context ctx = new InitialContext();
    ds = (DataSource) ctx.lookup("d:test/oracle");
    conn = ds.getConnection();
这块有问题，"d:test/oracle"这里是我的表空间存放数据文件的目录，以下是连接数据库的代码，运行时报错：
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


/**
*
*/
package com.cattsoft.util;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

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

/**
* @author Administrator
*
*/
public class ConnOracle {

private DataSource ds;
private Connection conn;
private PreparedStatement ps;

/*
<Resource name="DTmobile" auth="Container" type="javax.sql.DataSource"
driverClassName="oracle.jdbc.OracleDriver"
url="jdbc:oracle:thin:@127.0.0.1:1521:orcl"
username="cattsoft"
password="catts