Set a Pub Sub topic in Micronaut as per environment

Question

I am following this guide to initialise a GCP Pub/Sub publisher.

The coding syntax is as follows:

@PubSubClient
public interface PubSubService {

    @Topic("topic-a")
    void send(final A a);

    @Topic("topic-b")
    void send(final B b);

}

I want to set this topic value based on the environment, as I will have a different topic for QA/DEV (say topic-a-qa and topic-b-qa). Is there any way for me to set this String value in the @Topic annotation via or based on environment properties?

I do not have an option of have a different Project under the GCP account, also creating a different class for QA overriding this one is not so graceful when maintaining environments.

Answer 1

You can use placeholders inside Micronaut's annotations.

@PubSubClient
public interface PubSubService {

    @Topic("${topic.a.name:topic-a}")
    void send(final A a);

    @Topic("${topic.b.name:topic-b}")
    void send(final B b);

}

The expression ${topic.a.name:topic-a} instructs Micronaut to search for the value in the configuration under the topic.a.name key, and fall back to the value topic-a if the configuration key is not found. Then you can configure different topic names using e.g. application-qa.yml configuration file:

_{src/main/resources/application-qa.yml}

topic:
  a:
    name: topic-a-qa
  b:
    name: topic-b-qa

Lastly, just make sure that when you run the application in the QA environment you set a proper active environment, e.g.

$ java -Dmicronaut.environments=qa -jar myapp.jar