How can I use environment specific variables in micronaut? - kotlin

Question

I'm new to micronaut and server side programming in general. The micronaut documentation, unfortunately, does not make a lot of sense to me, as I do not have a Java background. A lot of the terms like "ApplicationContext" make sense in english, but I have no idea how to use them in practice.
Trying to start with a very basic app that prints different configurations ("localhost", "dev", "prod") depending on the environment it is in.
Here's my controller
#Controller("/")
class EnvironmentController {
// this should return "localhost", "DEV", "PROD" depending on the environment
#Get("/env")
#Produces(MediaType.TEXT_PLAIN)
fun env() = "???" // what should I put here ?
// this should return the correct mongodb connection string for the environment
#Get("/mongo")
#Produces(MediaType.TEXT_PLAIN)
fun mongo() = "???" // what should I put here ?
}
Here's the application.yml. Ideally I'd have 1 yml file for each environment
micronaut:
application:
name: myApp
server:
port: 8090
environment: localhost
mongodb:
uri: 'mongodb://localhost:27017'
Application.kt is untouched with the rest of the files generated by the mn cli tool. How can I set per environment parameters, or pass the yml file as a parameter when starting micronaut?
Are there any conventions around this?

Answer 1

You can specify an environment with -Dmicronaut.environments, or by specifying them in the context builder Micronaut.run in your Application class.
https://docs.micronaut.io/latest/guide/index.html#environments
Then for example application-env.yml will be loaded.
https://docs.micronaut.io/latest/guide/index.html#propertySource
The docs are pretty clear on this

Answer 2

By default Micronaut only looks for application.yml. Then, for tests,dev and prod, it loads application.yml and overrides any values there with the ones defined in application-test.yml, application-dev.yml and application-prod.yml
If you want to enable any other environment, you need to do it manually
public static void main(String[] args) {
Micronaut.build(args)
.mainClass(Application.class)
.defaultEnvironments("dev")
.start();
}
https://docs.micronaut.io/latest/guide/index.html#_default_environment