我用以下代码来实现数据库的访问，

<%@ page contentType="text/html;charset=gb2312" language="java" import="javax.naming.Context,javax.sql.DataSource,javax.naming.InitialContext,java.sql.*"%>
<%
DataSource ds=null;
try
{
Context ininCtx=new InitialContext();
Context envCtx=(Context)initCtx.lookup("java:comp/env");　　　这句的initCtx这里出错了
//给出JNDI上下文，返回数据源
ds=(DataSource)envCtx.lookup("jdbc/wagl");
//获得数据库连接
if(ds!=null)
{
out.println("connection is ok!");
out.println("<br>");
Connection conn=ds.getConnection();
Statement stmt=conn.createStatement();
ResultSet rs=stmt.executeQuery("select * from Student");
while(rs.next())
{
out.println(rs.getString("ID"));
out.println(rs.getString("Name"));
out.println("<br>");
}
}
else
out.println("fail!");
}
catch(Exception e)
{
out.println(e);
}
%>

请教一下这一句是什么意思，要怎么改才能正确
谢谢