public class BaseUser{
 private long id;
 @NotNull
 private String lastName;
}

public class SuperUser extends BaseUser{
 private String firstName;
}

@Controller
public class EditUser{

 @RequestMapping(value="/edituser",method=RequestMethod.GET)
 public String getForm(@RequestParam("userType")long userType,Model model){
   model.addAttribute(getUserByType(userType));
   return "form";
 }

 private BaseUser getUserByType(long typeId){
   if(typeId==1){
     return new BaseUser();
   }
   else{
    return new SuperUser();
   }
 }

 @RequestMapping(value="/edituser",method=RequestMethod.POST)
 public String postForm(@Valid BaseUser baseUser,Binding result){
  if (result.hasErrors())
    return "form";
  else{
  //some actions , casting to type base or super user
  return "next";
  }
 }
}