请问service这么写有没有问题?

public interface Service {

	Dao dao = Server.getInstance().getIoc().get(Dao.class);
}

public interface UserService extends Service{

	public void saveAppUser(AppUser user);	
}

@IocBean(name="userService")
public class UserServiceImpl implements UserService{

	public void saveAppUser(AppUser user) {
		dao.insert(user);
	}
	
}