Allow `DeadLetterPolicy.deadLetterTopic` to be non-fully-qualified

[onobc]

Current Behavior

Currently, the DeadLetterPolicy.deadLetterTopic must be fully-qualified or it will not be able to find the topic to send the dead message to.

Note

It may currently allow a relative topic when the defaults.topic.[tenant|namespace] are not specified in application.yml but need to verify this.

Desired Behavior

When the DeadLetterPolicy.deadLetterTopic is not fully-qualified , it should automatically use the project’s default tenant and namespace configuration. This way, we wouldn’t need to manually write the full path in every DeadLetterPolicy, making the configuration more intuitive and less error-prone.

Note

Discovered in 1216

[therepanic]

Hi, @onobc! It doesn't look too complicated, I would offer my help if you don't mind.

[onobc]

Hi @therepanic ! Yes, please do 🥳

We do auto-fully-qualify in most locations, namely:

• PulsarAdmin
• DefaultPulsarReaderFactory
• DefaultPulsarProducerFactory
• DefaultPulsarConsumerFactory

Look at the DefaultPulsarConsumerFactory#ensureTopicNamesFullyQualified method for an example.

The trick in this case will be to post-process the deadLetterPolicy specified on the @PulsarListener and we can do something similar in one of the following locations:

• org.springframework.pulsar.config.MethodPulsarListenerEndpoint#setDeadLetterPolicy
• org.springframework.pulsar.annotation.PulsarListenerAnnotationBeanPostProcessor#resolveDeadLetterPolicy

I have not thought about which location is best suited but will need to be sure we have the default available at this time.

Also don't forget our Reactive counterpart @ReactivePulsarListener 😸

[oneby-wang]

Hi, @onobc Chris, if this fix feat: Allow DeadLetterPolicy.deadLetterTopic to be non-fully-qualified #1241 is ok, I'll create a pull request.

[therepanic]

Hi, @oneby-wang. Like you see, I already working on this, thanks. I will make PR soon.