.java

@Controller
@RequiredArgsConstructor
public class ExampleController {
  
    private final ExampleService exampleService;
  
    private final AccountRepository accountRepository;

    @PostMapping("/email-login")
    public String sendEmailLoginLink(String email
            , Model model
            , RedirectAttributes attributes) {
        Account account = accountRepository.findByEmail(email);

        if (account == null) {
            model.addAttribute("error", "유효한 이메일 주소가 아닙니다.");

            return "account/email-login";
        }

        if (!account.canSendConfirmEmail()) {
            model.addAttribute("error", "이메일 로그인은 1시간 뒤에 사용할 수 있습니다.");

            return "account/email-login";
        }

        exampleService.sendLoginLink(account);
        attributes.addFlashAttribute("message", "이메일 인증 메일을 발송했습니다.");

        return "redirect:/email-login";
    }
}


@Service
@Slf4j
@Transactional
@RequiredArgsConstructor
public class ExampleService {

    private static final String EXAMPLE_LINK_TEMPLATE = "템플릿 경로";

    private final TemplateEngine templateEngine;
  
    private final EmailService emailService;

    public void sendLoginLink(Account account) {
        account.generateEmailCheckToken();
        Context context = getContext(account);
        String message = templateEngine.process(EXAMPLE_LINK_TEMPLATE, context);

        EmailMessage emailMessage = EmailMessage.builder()
                .to(account.getEmail())
                .subject("이메일 제목")
                .message(message)
                .build();

        emailService.send(emailMessage);
    }

    private Context getContext(Account account) {
        Context context = new Context();
        context.setVariable("name", account.getName());
        context.setVariable("message", "메일 메시지");

        return context;
    }
}