JDBC-ODBC桥连接SQLSERVER的问题，谢谢

大家好，问题一个，能否请指教：是JSP的 JDBC-ODBC桥连接SQLSERVER的TOMCAT，SQL SERVER2000 FOR JDBC，SQL SERVER2000 SP3都已安装，ODBC设好了，CLASSPATH环境变量也设好了
代码是：
   <%@ page import="java.sql.*"%>
<%@ page import="java.text.*"%>
<%@ page import="java.util.*"%>
<html>
<head><title>sdf</title></head>
<body>
sdfasdfadfsdfasdfadfsdfasdfadfsdfasdfadf
<%   Class.forName("sun.jdbc.odbc.JdbcOdbcDriver").newInstance();
   Connection con=DriverManager.getConnection("jdbc:odbc:ggy","gg","gg");
   Statement sql=con.createStatement();
   ResultSet rs=sql.executeQuery("SELECT * FROM student");
  
%><%=rs.getString("sd")%>
<%
   con.close();
%>
   
</body>
</html>但还是出错，提示是：
javax.servlet.ServletException: [Microsoft][ODBC 驱动程序管理器] 未发现数据源名称并且未指定默认驱动程序
org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:825)
org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:758)
org.apache.jsp.text_jsp._jspService(text_jsp.java:160)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:94)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:324)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)同样的设置我用驱动连接又成功，驱动代码是：
    <%@ page contentType="text/html; charset=GBK" language="java" import="java.sql.*,java.io.*"%>
<html>
<body>
以下是从Ms sql server数据库读取的数据：<hr>
<table border=1>
<tr><td>id</td><td>书名</td><td>出版社</td><td>价格</td></tr>
<%! String trans(String chi)
{
               String result = null;
               byte temp [];
               try
               {
                       temp=chi.getBytes("iso-8859-1");
                      result = new String(temp);
                }
                catch(UnsupportedEncodingException e)
                {
                        System.out.println (e.toString());
                }
   return result;
}
%>
<%   Class.forName("com.microsoft.jdbc.sqlserver.SQLServerDriver").newInstance();
   Connection con=java.sql.DriverManager.getConnection("jdbc:microsoft:sqlserver://127.0.0.1:1433;DatabaseName=MJ","gg","gg");
   Statement stmt=con.createStatement();
    ResultSet rst=stmt.executeQuery("select * from student;");
    while(rst.next())
    {
     out.println("<tr>");
     out.println("<td>"+trans(rst.getString("sd"))+"</td>");
     out.println("<td>"+trans(rst.getString("sdf"))+"</td>");
     out.println("<td>"+trans(rst.getString("ae"))+"</td>");
   
     out.println("</tr>");
    }
    
    rst.close();
    stmt.close();
    con.close();
    %>    
</table>
</body>
</html>