class UserController{
  private MailSender mailSender;
  private UserService userService;
  public UserController(UserService userService, MailSender mailSender)
  public renderHtml(List<User> users);
}

class MailSender{
  private MailTemplate mailTemplate;
  public void sendEmailTo(String email,String content);
}

class UserService{
  private DBConnection conn;

  public List<User> getUserList();
  public User getUserByEmail(String email);
}