RetryTopicBootstrapper's internal bean cannot be overriden

[celcius112]

For more information please read this discussion and propositions by @garyrussell and @tomazfernandes: #1914.

As discussed in the discussion above, it is apparently possible to override internal beans in RetryTopicBootstrapper, for instance:

  @Bean("internalDeadLetterPublishingRecovererProvider")
  public DeadLetterPublishingRecovererFactory retryTopicConfiguration(DestinationTopicResolver destinationTopicResolver) {
    return new DeadLetterPublishingRecovererFactory(destinationTopicResolver);
  }

However, after testing in a Spring Boot application, it does not seem to be possible, since RetryTopicBootstraper is bootstraped before the application configuration, as seen in this demo application:
demo 2 2.zip

[celcius112]

As a side note I think overriding internal beans is a bit error-prone, since the internals might be modified without the users being notified. As an example I will take the package-private bean names in RetryTopicInternalBeanNames, which I guess can be modified without us knowing.

[tomazfernandes]

Hello @celcius112 and @garyrussell, thanks for bringing this up. I've ran the demo and from what I can tell the bean overriding works as expected.

The RetryTopicBootstrapper only registers the beans if none is found in the container under the same name, and the actual instantiation happens on demand when the container needs the bean for some other classes' constructor, which is why it stops in the @bean breakpoint after executing the bootstrapper logic.

You can check that the instance that gets injected into ListenerContainerFactoryConfigurer is the one that gets created through the @bean method.

As for the bean names, that's a good point! I'm ok with making them public and considering them part of the public API so that users can safely override them. I'd like to hear @garyrussell's take on this.

Thanks a lot for bringing this issue, and I hope the feature has been serving you well!

[garyrussell]

Hi @tomazfernandes I am fine with making the bean names public.

[celcius112]

@tomazfernandes thank you for the change and your time !

For the demo that's on me. I did not think

		BeanDefinitionRegistry registry = (BeanDefinitionRegistry) this.applicationContext;
		if (!registry.containsBeanDefinition(beanName))

would work before the overridden bean was created. The Spring's internal are still a bit obscure to me :)