jsp 连接问题，来啊

我想用学号作为关键字，查看该生的个人信息，但是由于刚接触，有的还不明白，请高手指点，帮我改正好吗
 运行时出现：
[Microsoft][ODBC Microsoft Access Driver] ???????? ?????? 'sno='null' ??代码如下
<html>
<head>
<title>信息查询</title>
</head>
<%@ page import="java.sql.*"%>
<body>
 <pre>
<%
  String Student_sno;
  Statement stmt; 
  Student_sno=request.getParameter("sno");  
  try{
     Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
     Connection  conn=DriverManager.getConnection("jdbc:odbc:ma");
 
stmt=conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);

ResultSet rs=stmt.executeQuery("select * from student where sno='"+Student_sno+"");
out.println("他的信息如下");
   while(rs.next()){
        out.print("姓名：");
        out.println(rs.getString("name"));
        out.print("性别:");
        out.println(rs.getString("sex"));
        out.print("学号:");
        out.println(rs.getString("sno"));
        out.print("生日：");
        out.println(rs.getString("birthday"));
        out.print("所在班级：");
        out.println(rs.getString("banji"));
        out.print("宿舍：");
        out.println(rs.getString("room"));   
        out.print("联系方式：");
        out.println(rs.getString("tel"));  
        out.print("家庭住址：");
        out.println(rs.getString("address"));
  
      }
rs.close();
    stmt.close();
conn.close();
     }
      catch(Exception ex){
      out.println(ex.getMessage()); 
       }    
%>
 </pre>
</body>
</html>