jsp用账号密码表登录后获取信息表的值.晕。闹不出来啊。空值！！

users表里面有userno,usersname,userpwd，role,字段，其中userno为主键，students表里面有stuno（主键），其中还是一些乱七八糟的信息。学生登陆后如何获取相应stuno的信息？跪求代码啊
下面是登录页的代码

<%@ page contentType="text/html; charset=gb2312" language="java" %>
<%@ page import="java.util.*"%>
<%@ page import="java.sql.*" errorPage=""%>
<%@ page session="true" %>
<HTML>
<HEAD>
<TITLE>登录验证</TITLE>

</HEAD>
<BODY>
<%
String user = new String(((request.getParameter("username")).trim()).getBytes("ISO-8859-1"));
String pass = new String(((request.getParameter("password")).trim()).getBytes("ISO-8859-1"));
String type = new String(((request.getParameter("role")).trim()).getBytes("ISO-8859-1"));
Class.forName("com.mysql.jdbc.Driver");
Connection con = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/ma?user=root&password=1234&useUnicode=true&characterEncoding=gb2312");
Statement stmt = con.createStatement();
String sql = "select role from users where username='" + user + "' and userpwd='" + pass + "' and role='" + type + "'";
ResultSet rs = stmt.executeQuery(sql);
if(rs.next()){
if(type.equals("1")){
session.setAttribute("username",user);
                     session.setAttribute("role",type);
                     response.sendRedirect("student/student.html");
}else if(type.equals("2")){
session.setAttribute("username",user);
                     session.setAttribute("role",type);
                     response.sendRedirect("teacher/teacher.html");

}else if(type.equals("0")){
session.setAttribute("username",user);
                     session.setAttribute("role",type);
                     response.sendRedirect("admin/admin.html");
}
   }

else
{
%>

<style type="text/css">

</style>

<meta http-equiv="Content-Type" content="text/html; charset=gb2312"><style type="text/css">

</style>

<DIV align=center>
  </TD>
  <IMG
      src="images/line.jpg"
      width=757 height=5 border=0>
  <TD width=21><p> </p>
        <table width="317" height="183" border="2" align="center">
              <tr>
                <td height="175" bgcolor="#9999FF"><p align="center" class="STYLE19 STYLE20"><span class="STYLE12">用户名不存在或密码错误。</span></p>
                  <p align="center" class="STYLE20 STYLE6">请<a href="index.html">重新登录</a>！</p></td>
              </tr>
            </table>
        <p> </p>
          <p> </p></TD>
    <TD vAlign=top width=503>
      <TABLE id=table2 cellSpacing=0 cellPadding=0 width="100%" border=0>
        <TBODY>
        <TR>          </TR></TBODY></TABLE>

</TD></TR>
  <TR>
    <TD height=52></TD></TR>
  <TR>
    <TD colSpan=3><IMG height=5
      src="file/line.jpg"
      width=757 border=0></TD>
  </TR>
  <TR>
    <TD height=15></TD></TR>
  <TR>
    <TD colspan="3">
      <P align=right>                     </P></TD>
</TR></TBODY>
</TABLE>
</DIV>

<%
}

rs.close();
stmt.close();
con.close();
%>
</BODY>
</HTML>
--------------------编程问答-------------------- 哪里为空呀,
String user = new String(((request.getParameter("username")).trim()).getBytes("ISO-8859-1"));
String pass = new String(((request.getParameter("password")).trim()).getBytes("ISO-8859-1"));
String type = new String(((request.getParameter("role")).trim()).getBytes("ISO-8859-1"));

你这三个都有值不呀? --------------------编程问答-------------------- 首先，楼主贴代码的时候最好能选择菜单栏第七个按钮，选择“插入源代码”
其次，楼主是哪里没有得到值呢？按位置输出一下，看看。 --------------------编程问答-------------------- 我想对楼主说的是，你的users表和students表的关联字段是什么，两个表没有联系怎么能取出信息呢 --------------------编程问答--------------------

--------------------编程问答-------------------- userName=new String(userName.getByte("ISO-8859-1"),"UTF-8") --------------------编程问答-------------------- 把出现问题的地方标出来 --------------------编程问答--------------------

补充：Java ,  Web 开发