Spring Boot @ControllerAdvice + @Transactional not working as expected

Question

I'm working on a bets website so transactions are very important. I created an ExceptionHandler using @ControllerAdvice to catch all the exceptions from business layer.

@ControllerAdvice
public class HttpExceptionHandler {

  private String getStackTrace(final Throwable throwable) {
    final StringWriter stringWriter = new StringWriter()
    final PrintWriter printWriter = new PrintWriter(stringWriter, true)
    throwable.printStackTrace(printWriter)
    stringWriter.getBuffer().toString()
  }

  private List<String> filterStackTrace(final String stackTrace) {
    def stack = stackTrace.split('\n\t')
    stack.findAll({ it.contains('com.dsindigo.trading') })
  }

  private ResponseEntity<HttpErrorResponse> buildResponse(final Exception ex, final String message) {
    HttpErrorResponse error = new HttpErrorResponse(
      stack: filterStackTrace(getStackTrace(ex)),
      message: message
    )

    new ResponseEntity<HttpErrorResponse>(error, HttpStatus.BAD_REQUEST)
  }

  @ExceptionHandler(UsernameAlreadyExistsException)
  ResponseEntity<HttpErrorResponse> catchUsernameAlreadyExists(final UsernameAlreadyExistsException ex) {
    buildResponse(ex, HttpErrorMessages.USERNAME_ALREADY_EXISTS)
  }

  @ExceptionHandler(EmailAlreadyExistsException)
  ResponseEntity<HttpErrorResponse> catchEmailAlreadyExists(final EmailAlreadyExistsException ex) {
    buildResponse(ex, HttpErrorMessages.EMAIL_ALREADY_EXISTS)
  }

  //More exceptions...

  @ExceptionHandler(Exception)
  ResponseEntity<HttpErrorResponse> catchAny(final Exception ex) {
    buildResponse(ex, HttpErrorMessages.UNKNOWN)
  }
}

So basically it catches an exception (eg. UsernameAlreadyExistsException) and creates a JSON response containing a custom message and the stacktrace (for debugging purposes).

This is an example of a service throwing custom exceptions:

@Service
class UserServiceImpl implements UserService {

  // @Autowired stuff ...

  @Override
  @Transactional
  UserDTO save(UserDTO user) {
    UserDTO current = findOneByUsername(user.username)

    if (current != null)
      throw new UsernameAlreadyExistsException()

    current = findOneByEmail(user.email)

    if (current != null)
      throw new EmailAlreadyExistsException()

    ConfigurationDTO configuration = configurationService.findOne();

    user.active = false
    user.password = bCryptPasswordEncoder.encode(user.password)
    user.balance = configuration.initialBalance

    User entity = mapper.map(user, User)
    entity = userRepository.save(entity)
    user = mapper.map(entity, UserDTO)

    transactionService.createForUser(user.id, INITIAL_CHIPS_ID, configuration.initialBalance)

    TokenDTO token = tokenService.createForUser(user.id)
    emailService.sendRegisterMessage(user.email, token.token)

    user
  }
}

The problem is, when I throw a custom exception without @Transactional the exception handler executes the right method but adding @Transactional always executes the general Exception method.

Am I missing something?

Answer 1

These declarations:

@ExceptionHandler(UsernameAlreadyExistsException)

Should be like this:

@ExceptionHandler(UsernameAlreadyExistsException.class)

Also, make sure that your exceptions are extending RuntimeException. If the exception is caught and handled anywhere else in your code (including Spring's interceptors!) it won't be handled by ControllerAdvice.