帮看一下HttpServletRequest的问题！！！

public class DepartmentManager {
//...
public void viewByNO(HttpServletRequest request,HttpServletResponse response)
throws ServletException, IOException{
try{
String depno=request.getParameter("depno");
if (depno==null) request.setAttribute("msg","null!");
else request.setAttribute("msg",depno);
//DepartmentMap dm=new DepartmentMap();
//Department dep=dm.load(depno);
//request.setAttribute("dep",dep);
}catch(Exception e){

}
}
//...
}

public class DepAndDutyServlet extends HttpServlet {
//..
protected void processRequest(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
depMan.viewByNO(request,response);
}

public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
processRequest(request,response);
}

public void doPost(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
processRequest(request,response);
}
//..
}

depno的值传不给DepartmentManager，怎么回事呀？