Spring Boot @Transactional annotation doesn't work

Question

My signupUser method saves a user and sends an email to the registered email address. If the email fails to be sent, the user data saved has to be rolled back. I've added @Transactional on the signupUser method but it doesn't roll back when an exception happens and the data gets permanently saved. I temporarily replaced the sending email part with simply throw RunTimeException to check if transactional would work but the result was the same (didn't roll back).

This method is called in a @Controller annotated class.

What am I doing wrong?

@Service
public class AuthService {

        private UserRepository userRepository;
        private final Logger logger = LoggerFactory.getLogger(AuthService.class);
        private CustomMailSender mailSender;
        private ModelMapper modelMapper;

        @Autowired
        private PasswordEncoder passwordEncoder;


    @Autowired
        public AuthService(UserRepository userRepository, CustomMailSender mailSender, ModelMapper modelMapper) {
            this.userRepository = userRepository;
            this.mailSender= mailSender;
            this.modelMapper = modelMapper;
        }

 
    @Transactional
      public void signupUser(SignUpForm signUpForm){
        userRepository.save(new User(signUpForm.getUsername(), passwordEncoder.encode(signUpForm.getPassword()), signUpForm.getEmail()));
        throw new RuntimeException("腹たつ");

        }

Answer 1

I found out it was the configuration on mySQL. I changed the engine from the default one to InnoDB and it worked!

Spring boot @Transactional doesn't rollback