Spring IllegalStateException while publishing events within a transactional reactive method if 'event listener' method has @Transactional annotation

Affects: Spring Boot 2.2.0.M3

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If we publish the events within the transactional reactive methods, for example:

@Transactional
public Mono<Model> create(Model model, ModelEvent.Type type) {
    return repo.save(model)
            .doOnSuccess(m -> publisher.publishEvent(new ModelEvent(m, type)));
}

then IllegalStateException is raised with a message:

Specified transaction manager is not a PlatformTransactionManager: org.springframework.data.mongodb.ReactiveMongoTransactionManager

if the 'event listener' method has @Transactional annotation (with MANDATORY parameter, for example, to check if we are really in the existent transaction):

@Transactional(propagation = Propagation.MANDATORY)
@EventListener(condition = "#event.withTransactional()")
public void handleEventWithTransactional(ModelEvent event) {
    log.info("[i] Handled event: {}, with transactional", event.getModel());
}

Detailed demo is here.

Comment From: snicoll

Unfortunately, what you're trying to do is not supported. See the note in the reference documentation. Using @EventListener the way you do and expect to run in the transaction is not accurate as the way events are fired can be asynchronous (which is why @TransactionalEvenListener exists in the first place).