Has anyone built something on Cloudflare Workers with Kotlin? Any gotchas or anything I should look out for? 🙏

Heya, have you run into other Kotlin/Java code generators from OpenAPI than https://github.com/OpenAPITools/openapi-generator/ and https://github.com/swagger-api/swagger-codegen ? They both leave a lot to be desired on the generating model classes side (not to mention, say, clients) with quite buggy implementations compared to, say, OpenAPI Typescript generator.

I’m trying to setup a Spring Boot (3.1.0) app with Spring security (default version for Spring Boot 3.1.0). I’m having trouble setting up a

JwtDecoder

bean due to an ambiguous constructor in a java class The error I get is:

/auth0/my-auth0-demo/auth0/src/main/kotlin/com/curbee/auth0/SecurityConfig.kt:48:7
Kotlin: None of the following functions can be called with the arguments supplied: 

public constructor DelegatingOAuth2TokenValidator<T : OAuth2Token!>(vararg tokenValidators: OAuth2TokenValidator<TypeVariable(T)!>!) defined in org.springframework.security.oauth2.core.DelegatingOAuth2TokenValidator

public constructor DelegatingOAuth2TokenValidator<T : OAuth2Token!>(tokenValidators: (Mutable)Collection<OAuth2TokenValidator<TypeVariable(T)!>!>!) defined in org.springframework.security.oauth2.core.DelegatingOAuth2TokenValidator

To help assist, the constructors for the class in error: `DelegatingOAuth2TokenValidator.java`:

public DelegatingOAuth2TokenValidator(Collection<OAuth2TokenValidator<T>> tokenValidators) {
		Assert.notNull(tokenValidators, "tokenValidators cannot be null");
		this.tokenValidators = new ArrayList<>(tokenValidators);
	}

	@SafeVarargs
	public DelegatingOAuth2TokenValidator(OAuth2TokenValidator<T>... tokenValidators) {
		this(Arrays.asList(tokenValidators));
	}

I’ve tried all kinds of combinations to try and get this to compile. e.g. •

DelegatingOAuth2TokenValidator<OAuth2TokenValidator<Jwt>>(withIssuer)

•

DelegatingOAuth2TokenValidator<OAuth2TokenValidator<Jwt>>(*withIssuer)

•

DelegatingOAuth2TokenValidator<OAuth2TokenValidator<Jwt>>(listOf(withIssuer))

•

DelegatingOAuth2TokenValidator<OAuth2TokenValidator<Jwt>>(*listOf(withIssuer))

•

DelegatingOAuth2TokenValidator<OAuth2TokenValidator<Jwt>>(java.utils.Arrays.asList(withIssuer))

I could use some help figuring how to give a hint to which consructor

I am trying to understand how to properly use the Repository pattern when creating a backend server. Should its functions be strictly CRUD like, or is it acceptable to have some use-case-specific "logic" related to the Entities it works represented there? For example, is this something I should rather split?

sealed class Event {
    abstract val receivedAt: Instant
    abstract val occurredAt: Instant
    ...

    data class Incoming(
        override val receivedAt: Instant,
        override val occurredAt: Instant,
        ...
    ) : Event()

    sealed class Stored : Event() {
        abstract val authorUid: ULong

        data class Pending(
            override val receivedAt: Instant,
            override val authorUid: ULong,
            override val occurredAt: Instant,
           ...
        ) : Stored()

        data class Uploaded(
            override val receivedAt: Instant,
            override val authorUid: ULong,
            override val occurredAt: Instant,
            ...
            val uploadedAt: Instant
        ) : Stored()
    }
}

interface EventRepository {
    fun storeEvent(authorUid: ULong, event: Event.Incoming): Event.Stored.Pending
    fun confirmEvent(event: Event.Stored.Pending, uploadTime: Instant = Instant.now()): Event.Stored.Uploaded
    fun getEvents(): Collection<Event.Stored>
    fun getEventsCount(): ULong
    fun pendingEvents(): Collection<Event.Stored.Pending>
    fun pendingEventsCount(): ULong
}

Not sure this is the right place, but for the life of me I cannot figure out what is going wrong with a command I am trying to run. I want to use the ProcessBuilder api to run a command, but it is erroring out. my code

fun String.runCommand(workingDir: File): ProcessUtils.Result {
    val parts = this.split("\\s".toRegex())
    val proc = ProcessBuilder(parts)
      .directory(workingDir)
      .redirectOutput(ProcessBuilder.Redirect.PIPE)
      .redirectError(ProcessBuilder.Redirect.PIPE)
      .start()

    proc.waitFor(60, TimeUnit.SECONDS)
    val exitCode = proc.exitValue()
    val outputText = proc.inputStream.bufferedReader().readText().trim()
    return ProcessUtils.Result(exitCode, outputText)
  }

I have confirmed that

_workingDir.exists_() && _workingDir_._isDirectory_()

is true, but when the proc starts, it errors out with a dir not found error. Cannot fathom how the first statement can be true (confirmed dir does exist) but the proc cannot find it. My only guess is a permissions issue, but I cant find anything to confirm this is the case. Anyone have any ideas?

Hi everyone! Not sure if this is the right place, but it was the best that I found for the question I’m planning to start a new backend project using Kotlin and I was wondering about the options of web framework to use. I know Spring is a pretty solid one, but maybe there are others more suited for Kotlin specific applications. So, what web frameworks do you guys recommend?

Hi, I'm trying to develop a ktor application, which has a lot of user-generated "structures", similar to Notion databases. I would want to give the user the capability to do standard stuff like sort, filter etc. with these structures. In this sense, does it make sense for me to use ORMs for that? do I still get the advantages of syntactic sugar and safety?

Hello, I am trying to run Kotlin on Jupyterhub. I am having a problem with reading this jar file from time to time. It works some time (after repeating calling the code) but fails very often. Can someone point me to the right direction to look please?

@file:Repository("https://repo1.maven.org/maven2") @file:DependsOn("org.apache.logging.log4jlog4j api2.20.0") var c = org.apache.logging.log4j.util.Constants.EMPTY_BYTE_ARRAY c

This is just to test whether I can access a field/method of a jar.

It may give an error often: Line_34.jupyter.kts (3:49 - 65) Unresolved reference: EMPTY_BYTE_ARRAY So, it can't find that particular field in the jar, but other fields can be found. Just not this one. I wonder why...

Hi everybody, i have a micronaut application with kotlin and gradle kotlin dsl. I want to pass env variables, such as DB_PASS=“XXX” DB_NAME=“XXX”, such that i can access them in main function. What is the best way to do it? My initial thought was to use gradle properties (-P) but i can’t seem to get them working. Any expert who knows what to do here?

plugins {
    id("org.jetbrains.kotlin.jvm") version "1.8.20"
    id("org.jetbrains.kotlin.plugin.allopen") version "1.8.20"
    id("com.google.devtools.ksp") version "1.8.20-1.0.10"
    id("com.github.johnrengelman.shadow") version "8.1.1"
    id("io.micronaut.application") version "4.0.0-M2"
}

version = project.properties["version"] as String? ?: "0.0.1"
group = "dk.****"

val kotlinVersion = project.properties["kotlinVersion"]
repositories {
    mavenCentral()
}

dependencies {
    implementation("io.micronaut:micronaut-jackson-databind")
    implementation("io.micronaut.kotlin:micronaut-kotlin-runtime")
    implementation("io.micronaut:micronaut-management")
    implementation("org.jetbrains.kotlin:kotlin-reflect:${kotlinVersion}")
    implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8:${kotlinVersion}")
    runtimeOnly("ch.qos.logback:logback-classic")
    runtimeOnly("com.fasterxml.jackson.module:jackson-module-kotlin")
    testImplementation("io.micronaut:micronaut-http-client")
}

application {
    mainClass.set("dk.***.ApplicationKt")
}
java {
    sourceCompatibility = JavaVersion.toVersion("17")
}

tasks {
    compileKotlin {
        compilerOptions {
            jvmTarget.set(org.jetbrains.kotlin.gradle.dsl.JvmTarget.JVM_17)
        }
    }
    compileTestKotlin {
        compilerOptions {
            jvmTarget.set(org.jetbrains.kotlin.gradle.dsl.JvmTarget.JVM_17)
        }
    }
}
graalvmNative.toolchainDetection.set(false)
micronaut {
    runtime("netty")
    testRuntime("kotest5")
    processing {
        incremental(true)
        annotations("dk.***.*")
    }
}

[Different Database for Testing] TL;DR : if you know how to properly use different KMongo databases when testing pieces of code that statically reference a database variable, you might just be my saviour Hi everyone, I apologise in advance if this message has nothing to do here, please do say so if it is the case. I'm working on a web-app with Kotlin MPP which I am discovering. I am starting to want to develop a test base to have healthier code practices, but I ran into a problem when wanting to test my KMongo database accesses for the Kotlin/JVM part. My controller (and test class) access MyService 's methods which are stored in its companion object

val myCollection = database.getCollection<Object>()
class MyService {
    companion object {
        suspend fun myMethod(){
            myCollection.doSomething()
        }
    }
}

The issue is that the

database

object called here is imported from my Server class where it is imported as such:

val client = KMongo.createClient().coroutine
val database = client.getDatabase("debug_name")
fun main(args: Array<String>): Unit = io.ktor.server.netty.EngineMain.main(args)

Now, this worked perfectly until I needed to test it (I know I should've started by the tests, my bad) The issue is that, as it is, when my test class calls

MyService.myMethod()

, the collection used is the "debug_name". I have instantiated another database in the

@BeforeClass

method from my test class, but I can't figure out how to use it. My different ideas so far have consisted of : • using a constructor for the Service class with the database to use, which I know is not a good solution • detecting the type of build running to pass a different parameter to the

getDatabase()

method (maybe via environment variables?), but I feel like this would not be optimal at all and kind of go against the idea behind testing philosophy, as it sould still be using the

database

variable stored in the

Server

file instead of a controlled test-environment database I am absolutely unsure of how to go about this and nothing I have tried has even started to work a tiny bit. If you have insights on how to properly do this, I'd be super grateful ! A wannabe-programmer

Hello, not sure if this is the best place to post the question, but here we go: Is there a way to define the resolution that Kotlin uses for `Instant`s? Reason: Our Kotlin application talks to a PostgreSQL database and saves `Instant`s in a

timestamp

column. PostgreSQL has microsecond resolution for that column. On MacOS, this works because

Clock.System.now()

also returns an

Instant

with microsecond resolution, so comparing an object before persisting it and after retrieving it from the database works. On Linux (which we use for our pipeline) this same comparison fails because

2023-06-09T07:34:27.965341799Z != 2023-06-09T07:34:27.965342Z

I found similar issues for e.g. H2, but there it seems possible to simply store nanoseconds in the database. It is not necessarily an issue to change the tests, we can simply set fixed instants (without nanosecond precision), but the question remains nevertheless: Is there a way to force Kotlin to always use a specific precision?

Hi everyone. I'm trying to use kotlin fixtures to create a builder object:

package bla.testdoubles.stubs

import bla.testdoubles.TreehouseTestFixture
import bla.testdoubles.fakes.FakeRequest
import bla.ServiceRequest

typealias Builder = ServiceRequest.ServiceRequestBuilder<FakeRequest>

val FakeRequestFixture = MyCustomTestFixture<FakeRequest> {
}

val ServiceRequestFixture = MyCustomTestFixture<Builder> {
    property<Builder, FakeRequest>(Builder::request) {
        FakeRequestFixture
    }

    property<Builder, String>("fullRequestURI") {
        // TODO: use Faker
        "123"
    }
}

The compiler says that

Builder::request

is a private member and cannot be accessed. I'm trying to refer to the automatically generated setter and not the private request variable that the Builder declared. This is the error:

Cannot access 'request': it is private in 'ServiceRequestBuilder'

The generated setter uses the

setRequest

method and that should be public. What am I doing wrong here?

Hi ! I am making utils for reflection with kotlin. However, I would like to get information through Annotation about what to change to when the variable is classed. However, after debugging, not only the field of Annotation but also the Annotation itself could not be searched in Reflection. How can I approach it?

@Target(AnnotationTarget.FIELD)
@Retention(AnnotationRetention.RUNTIME)
annotation class ReflectionTarget(
    val clazz: KClass<out Any> = Any::class,
)

data class UserInfo(
    val name: String,
    @ReflectionTarget(clazz = UserDetailsResponse::class)
    val userDetails: UserDetails,
)

data class UserDetails(
    val age: Int,
    val email: String,
)

How can I get the information of annotation and the field of annotation by reflection using the code below on runtime?

Hey, I’m having a heck of a time. I want to write a Kotlin command line app (for Linux) that makes a machine with a wifi card into a wifi direct group owner, then listens on a particular port on the wifi direct interface for incoming socket connections. Does anyone have a non-Android example in Kotlin or Java that makes a machine a wifi direct group owner then uses

ServerSocket

or similar to listen on a particular port for wifi direct group members to connect to?

Hey there guys, I have been learning the Ktor framework. The learning has been really nice and I have been trying to do a deployment of a small auth service I had written. I am deploying the jar to elastic-beanstalk and have been unsuccessful a couple of times. My environments are being terminated even before the deployment finishes. Who might happen to know why this is so? Any articles on deployments that worked for you guys would be highly appreciated.

Hey guys, wondering if there’s a way to use Kotlin value classes (inline classes) in JAX-RS. I had created a data class with properties of value class types. I couldn’t get my data class with parameters which have value class types as the request body in JAX-RS. I’m wondering if there’s any work around to get this working.

🎉 Hey everyone! Exciting news - http4k v5 has dropped. Feel free to give it this reddit post some love and share the news! both http4k and http4k-connect v5 are available now from Maven Central! 🎉 https://www.reddit.com/r/http4k/comments/14f6apy/http4k_platform_v5_new_servers_loom_tracerbullet/

hello everyone 🙂 I am attempting to make with kotlin a desktop application that listens to port(s) for messages and returns responses (i.e. input output). It will only be handling requests from host user (from web browser). This seems like a tcp/ip application. I want to make this as lightweight as possible. From these requirements, ktor seems like possibly overkill for library choice . Using a jetty (not netty) or cio (avoiding http layer) seems like the most lightweight options . But maybe I should avoid ktor all together because it would be great to not use a servlet. My first solution (for mvp) was just a while loop that listens for messages on ports, and then I deserialized with code I wrote, etc. So what I am looking for is a library that could do this (that I wont have to maintain, and is hopefuly better then just a while loop) that does not use a servlet (because It is over kill)

Hi! So I'm trying to create a simple multiplayer web game using Ktor, but am confused about how I should properly update UI on the client side. For example, If Player 1 wins the game, I would like to show, "You have won the game!" to Player 1 and, "Player 1 has won" to Player 2. Should I send the display text to each of the clients from the server, or should the clients just be told which player has won and determine what to display based on that? Or, does it not really matter?

Hi! I am currently working on a new validation library (yet another) and I want to be sure it fits your expectations. I've created a short survey (5 questions only) to gather facts about validation usage inside Kotlin's ecosystem. I would be really grateful if you could take a few minutes of your time to answer and help me with this project. 🙏 https://forms.gle/wfX9cte8GYhpiQTp6

Hello! Not sure if this is the correct place to ask, but is there something like

numpy

for kotlin? I was copying a small script I have for border detection from python to kotlin and stuff like matrix operations were a pain to do.

Hi, so I have an object that has a bunch of normal fields, and then it has an array field with enums in it. I have the object stored in the table with an integer ID, but I'm not quite sure how to store the array, I assume I need another table, but I'm not sure how to link it all together. Also, I need to make sure the order of the array is retained inside the table. Any and all help would be greatly appreciated!

Is there a way to access route parameters inside of an

authenticate(...)

call in Ktor? Alternatively, is there a way to update a session every time a route is called without having to call a function inside of each endpoint handler? Edit: I ended up solving this using the alternative solution with custom plugins to update the session.

Hi, I’m looking into redirecting a RTMP publish stream through my Ktor backend to another streaming server. This streaming server is only accessible via my backend. I see that with Netty as my Ktor server engine I can handle RTSP streams, but I cannot seem to find any ‘recent’ resources on this with RTMP. In short: RTMP publish stream to an endpoint on my backend -> do some operations in my backend -> forward this RTMP publish stream towards my streaming server. Any answer towards the right direction is appreciated!

RE verifying JWTs with AWS KMS. It's possible to call the KMS API for every single verification, but it seems possible to download the KMS public key and then proceed to use that. Undoubtedly, this is the ideal route for long-lived applications, but it's less clear for serverless applications on AWS Lambda, where cold-start is important to optimize for. It seems to me that downloading and using the public key would always be slower the first time rather than just verifying with the API. However, I haven't yet tested this. Does anyone have any experience with this tradeoff?

K ktor 🪙 Hello Kotlin community! This is my first post here hope it might help someone! With the release of mongodb kotlin integration, I'm creating a template repository to see how easy to use it is The repository can be found here: https://github.com/tkrason/ktor-koin-mongodb-template Honestly, my first impressions are extremely positive and I would say that stack of: • Ktor • Koin • MongoDB seems to be super powerful! Especially the seemingly seamless saving of data classes. Does anyone know about some projects that are already implementing similar stack?

Hey team, I’m running into an issue where the

compileKotlin

task when trying to build my kotlin project is infinitely looping. I left it running and as we can see it didn’t finish for 1.5 hours. I don’t think I changed anything in particular other than upgrading the kotlin plugin on Intellij. Is anyone else facing this recently? Some metadata if anyone finds it useful:

kotlin("jvm") version "1.7.21"
distributionUrl=https\://services.gradle.org/distributions/gradle-7.3-bin.zip

I tried changing the kotlin compiler to use the experimental K2 as well but no luck. Unfortunately its blocking some critical development that needs to happen in my organization so any advice would be much appreciated! 🙏