How to use Micronaut & depenency injection in a single-file Groovy script? - groovy

Question

I want to use Micronaut from a Groovy script. It seems that annotations such as #Inject and #PostConstruct are not processed.
Here is the code I tried:
#!/usr/bin/env nix-shell
#!nix-shell -i groovy
#Grapes([
#Grab('ch.qos.logback:logback-classic'),
#Grab('io.micronaut:micronaut-runtime')
])
package org.sdf // NPE without package
import io.micronaut.runtime.Micronaut
import javax.inject.*
import javax.annotation.*
#Singleton
class Component {
}
#Singleton
class App implements Runnable {
#Inject
Component comp
#Override
#PostConstruct
public void run() {
// Never runs
assert this.comp != null
assert false
}
}
static void main(String... args) {
Micronaut.run(App, args);
}
It doesn't run post-construct method and logs this:
22:17:43.669 [main] DEBUG i.m.context.DefaultBeanContext - Resolved bean candidates [] for type: interface io.micronaut.runtime.EmbeddedApplication
22:17:43.671 [main] INFO io.micronaut.runtime.Micronaut - No embedded container found. Running as CLI application
How can I use Micronaut with dependency injection in a single-file Groovy script?

Answer 1

How can I use Micronaut with dependency injection in a single-file
Groovy script?
You would have to compile all of the code in your script with Micronaut's annotation processors configured on the compile time classpath for your script. Technically that could be done with a single script but as a practical matter I don't think many folks are going to have a good reason to do or build support for making that more easily done.
FYI: Not an answer to your question as asked but one simple alternative approach is to not define all of your bean related classes in a single script, instead define them in their own separate source files in a project configured to build with Maven or Gradle using our annotation processors and then consume those classes from your script using #Grab like you have for other dependencies.