tomcat+SQL server2000数据连接池的有关问题？

tomcat+SQL server2000数据连接池的问题？？
代码：
      package   com.yl.test;


import   java.sql.Connection;
import   java.sql.ResultSet;
import   java.sql.Statement;

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

public   class   DBUtil   {
public   static   void   main(String[]   args)   throws   Exception
{
        DataSource   ds   =   null;
        Context   ctx   =   new   InitialContext();
        System.out.println( "0000000000000000 ");
if(ctx==null)
{
throw   new   Exception( "no   context ");
}
else
ds=(DataSource)   ctx.lookup( "java:comp/env/jdbc/test ");
System.out.println( "1111111111111 ");
Connection   con=ds.getConnection();
Statement   st=con.createStatement();
ResultSet   rs=st.executeQuery( "select   *   from   TABLE1 ");
while(rs!=null)
{
System.out.println( "name== "+rs.getString( "name "));
}
rs.close();
st.close();
con.close();
            }

}
报错
Exception   in   thread   "main "   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(Unknown   Source)
at   javax.naming.InitialContext.getDefaultInitCtx(Unknown   Source)
at   javax.naming.InitialContext.getURLOrDefaultInitCtx(Unknown   Source)
at   javax.naming.InitialContext.lookup(Unknown   Source)
at   com.yl.test.DUtil. <init> (DUtil.java:19)
at   com.yl.test.DUtil.main(DUtil.java:56)
各位英雄，帮忙看看在线等待啊，汗！

------解决方案--------------------
給一段例子你看看：

public Connection getConnectionByDBPool() {
Connection conn = null;
Context initCtx = null;
Object obj = null;

try {
initCtx = new InitialContext();

if(initCtx==null){
throw new Exception( "没有匹配的环境 ");
}

switch(DBServer) {
case 0: //tomcat
Context ctx = (Context) initCtx.lookup( "java:comp/env ");
obj = (Object) ctx.lookup(jndi_Name);
break;
case 1: // jboss
String jndi_name= "java:/ " + jndi_Name;
obj = (Object) initCtx.lookup(jndi_name);
break;
case 2: //weblogic
obj = (Object) initCtx.lookup(jndi_Name);
break;
}

DataSource ds = (javax.sql.DataSource)obj;

if (ds==null) {
throw new Exception( "没有匹配的数据库 ");
}
conn = ds.getConnection();

} catch (Exception e) {
e.printStackTrace();
}

return conn;
}