看下我的代码,哪里出错?
<%@page   import   = "java.sql.* "%>  
<%@   page   import= "java.io.* "%>  
<%@   page   import   = "java.util.* "%>  
<%
response.setContentType( "text/html;charset=8859_1 ");
request.setCharacterEncoding( "gb2312 ");
%>
<%  
String   name   = " ";
String   userId=request.getParameter( "j_username ");  
String   userPwd=request.getParameter( "j_password ");    
String   strSQL= "select   *   from   usermess   where   userid= ' "+userId+ " 'and   userpass= ' "+userPwd+ " ' ";  
int   count=0;  
if(userId.equals( " ")){%>
<script   language= "javascript "   type= "text/javascript ">
<!--
        alert( "您的用户名不能为空！ ");  
</script>
<%}
else   if(userPwd.equals( " ")){%>
    <script   language= "javascript "   type= "text/javascript ">
<!--
        alert( "您的密码不能为空！ ");  
</script>
<%}
else   {  
try   {  
Class.forName( "com.microsoft.jdbc.sqlserver.SQLServerDriver ");  
Connection   conn=DriverManager.getConnection( "jdbc:microsoft:sqlserver://192.168.50.60:1433;DatabaseName=student ", "sa ", "software ");  
Statement   st=conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE);  
ResultSet   rs=st.executeQuery(strSQL);  
if(rs.next())
{  
    count++;  
    System.out.println(count);  
}  
if(count> 0)
{    
    String   sql= "select   *   from   student   where   stuid   = ' "+userId+ " ' ";
    String   sql1= "select   *   from   teacher   where   teaid   = ' "+userId+ " ' ";
    String   sql2= "select   *   from   adminis   where   adminid   = ' "+userId+ " ' ";
    rs=st.executeQuery(sql);
    if(rs.next())
    {session.setAttribute( "loginuser ",userId);
    response.sendRedirect( "selectmain.jsp ");//进入学生主系统；
    }
    else  
    {
            rs=st.executeQuery(sql1);
            if(rs.next())
          {   session.setAttribute( "loginuser ",userId);
                      response.sendRedirect( "teachertmain.jsp ");
  }
    else
    {     rs=st.executeQuery(sql2);
          if(rs.next())
          {
  session.setAttribute( "loginuser ",userId);
                  response.sendRedirect( "adminmain.jsp ");
  }
    }