public String addUser() throws Exception{
		User user = new User(userid, username, userpassword);
		
		if (userService.saveOrUpdateUser(user)){ addActionMessage("User is added.");
		}else{ addActionMessage("Adding user failed."); }
		
		ServletOutputStream writer = null;
		try{
	        writer = response.getOutputStream();
	        writer.println("success");
	    } catch( Exception e ) { throw e;
	    } finally{ if( writer != null ) writer.close(); }
		
		return null;
	}