Using @QuarkusMain in Kotlin produces warnings on startup

[jehrenzweig-leagueapps]

I'm following the "Application Initialization and Termination" guide's instructions on how to add a custom startup method to a Quarkus application. The guide is written for Java but I'm using Kotlin; here's the code I've written thus far:

package com.leagueapps.microservices.poc.potato.application

import io.quarkus.runtime.Quarkus
import io.quarkus.runtime.annotations.QuarkusMain

@QuarkusMain
object ApplicationStartup {
	@JvmStatic
	fun main(args: Array<String>) {
		Quarkus.run(*args)
	}
}

The following item now appears in my log when the Quarkus application starts up:

2022-06-21 14:26:00,973 INFO  [io.qua.arc.pro.BeanProcessor] (build-31) Found unrecommended usage of private members (use package-private instead) in application beans:
	- Bean constructor void <init>() on com.leagueapps.microservices.poc.potato.application.ApplicationStartup

Are there any changes I can/should make to my code? The message doesn't really give me much to go on... my code doesn't declare any private member, and as far as I know Kotlin doesn't support making anything package-private through the use of visibility keywords. I also don't know what the Bean constructor void <init> on message means.

[quarkus-bot[bot]]

/cc @evanchooly

[jehrenzweig-leagueapps]

Through the power of trial and error, I found a Kotlin code solution that does not produce the warning:

import io.quarkus.runtime.Quarkus
import io.quarkus.runtime.annotations.QuarkusMain

@QuarkusMain
class ApplicationStartup {
	companion object {
		@JvmStatic
		fun main(args: Array<String>) {
			Quarkus.run(*args)
		}
	}
}

And this seems to be a way to declare a code block like the second one mentioned in the guide, but in Kotlin:

import io.quarkus.runtime.Quarkus
import io.quarkus.runtime.QuarkusApplication
import io.quarkus.runtime.annotations.QuarkusMain

@QuarkusMain
class ApplicationStartup {
	companion object {
		@JvmStatic
		fun main(args: Array<String>) {
			println("Running ApplicationStartup.main() method")
			Quarkus.run(MyApp::class.java, *args)
		}
	}

	class MyApp : QuarkusApplication {
		override fun run(vararg args: String): Int {
			println("Do startup logic here")
			Quarkus.waitForExit()
			return 0
		}
	}
}

[evanchooly]

In your first attempt, you were using a top level object. These are singleton by definition and uninstantiable because the constructor is private. your second attempt used an actual class whose default/noarg constructor is public by default. So when the static main is attached to that class, there's a public constructor. When it's attached to that object, there is not.

[jehrenzweig-leagueapps]

Great, thank you for that info. I figured there was a reasonable explanation for the behavior... I just wasn't finding it, & didn't know how to go about searching for it. Still learning the ropes w/ both Kotlin & Quarkus.