kotlinlang #server

Join us on May 10 for Event Streaming with Apache Pulsar and Kotlin. In this webinar, we will demonstrate how to enhance event-driven microservices with advanced capabilities, such as on-the-fly serialization or parallel processing. Save the date: https://kotl.in/9ya3p9

🎉 9

👍 5

Gillian Buijs

05/04/2022, 4:35 PM

Given a classic maven based Java EE app running on Websphere Liberty with Angular frontend, would it be feasible to port it to KMP? We started using Kotlin in the backend instead of Java. I would want to ditch the Angular frontend (it's old and made badly) and use React with Kotlin/JS. Primary benefit would be typesafe coupling between frontend and backend and using Kotlin for both (instead of TS yuck). Ideally I would want to use the backend as-is and keep the Gradle usage to a bare minimum because everything is maven based (company policy). Kind of a broad question I know, but if anyone has some experience/advice it's appreciated 👍

Marco Pierucci

05/05/2022, 4:00 PM

Hello! Is there any good alternative to KgraphQL ? Joined a team that was using this to mock a graphql endpoint on an android project. But seems that has usages of MethodHandle.invoke and MethodHandle.invokeExact which wont allow me to run under api 26

André Martins

05/05/2022, 4:18 PM

Hello, I’m trying to measure the time it takes to execute a function although I want to log the time it took even if the function throws any exception. I came up with this approach but seems ugly to me. What you guys think? Is there any other approach?

val (result, duration) = measureTimedValue {
    try {
        foo()
    } catch (ex: Throwable) {
        ex
    }
}
when(result) {
    is Throwable -> println("Error ${duration.inWholeMilliseconds} ms")
    else -> println("Success ${duration.inWholeMilliseconds} ms")
}

Kristian Nedrevold

05/05/2022, 6:41 PM

Is there a good database framework/abstraction layer in kotlin that uses a non-blocking driver? I am implementing a ktor backend with a postgres database, and am looking for something like jdbi that uses a non-blocking driver.

mbonnin

05/09/2022, 2:32 PM

Is there a public Docker image that comes with kotlin preinstalled that I could build upon ?

Jarkko Miettinen

05/10/2022, 10:24 AM

Hey, I ended up with doing silly things with Redis and storing a changed class there with same key as earlier. This of course blew up my retrieval code as older versions could not be deserialized from JSON anymore. Any thoughts on how versioning of such (data?) classes could be automated? I am thinking of creating a simple object graph traversal that mostly allows for simple collections and basic types. But that seems like a lot of work for something that I think has been solved already. So what's the best way to store potentially changing Kotlin objects, serialized as JSON, to Redis?

Kevin Del Castillo

05/10/2022, 10:15 PM

Is it wise to run an API server with Kotlin/Native or is it preferred to run it with the JVM for now?

Andrzej Sawoniewicz

05/13/2022, 2:17 PM

Hi guys. In our project there is a lot of boilerplate code and I am considering migrate to Kotlin. However we have 3 layers of model classes (ATO, actual model, DTO) and therefore we use mappers heavily (with complex composition structure). For now we use Remap but it is not working too well with Kotlin. I was considering to switch to MapStruct but it is also not supporting the Kotlin directly. There is a library to create builders automatically but it is rather simple and not supported anymore. What do you think would be the best solution here? Manual mapping, MapStruct or something else?

stvn

05/14/2022, 1:40 PM

Hey, im learning jwt-authorization with Ktor using this tutorial https://ktor.io/docs/jwt.html#flow , my question is for tips how to generate safe shared secret and is there some requirements for it? i’m planning storing it in Heroku config-var.

fulstaph

05/14/2022, 2:21 PM

Hello! I'm trying to implement web service usig Ktor and Exposed. The server itself works fine, but application tests are failing without an active database connection.

class ApplicationTest {
    @Test
    fun testRoot() = testApplication {
        val response = client.get("/")
        assertEquals(HttpStatusCode.OK, response.status)
    }
}

basically this sample test is failing because it seems like

testApplication

tries to init hikari conn pool. If I run database everything is ok. Can I substitute this w/ in memory database somehow? Or better yet, drop the DB connection altogether and use service layer mock? Sorry if the question is dumb, I have no experience with JVM ecosystem, would be glad to get any suggestions.

ESchouten

05/16/2022, 8:48 PM

Perhaps anyone at #server has interesting insights on this subject!

dave

05/17/2022, 9:06 AM

We're coming across this problem with LocalDynamoDB (the JAR of which still ships with a bundled Kotlin 1.3.72 and hence is basically incompatible with everything Kotlin if you want it in the same process!). Has anyone else worked around this - or even is there someone here who works for Amazon who can help to get it sorted? https://github.com/aws/aws-sdk-java-v2/issues/2487

BingZi233

05/17/2022, 11:31 PM

Hello, I have a problem. In the code below, I try to set up a static directory. Unfortunately, I ran into a 404 error. I looked at the WIKI example, but nothing improved.

Kristian Nedrevold

05/20/2022, 10:46 PM

Hey, does anyone know how I can parse 2022-05-20T19:36:27Z with kotlinx-datetime?

Alexis Cala Martínez

05/23/2022, 11:00 PM

Team i am not sure, but is there any kind of info about kotlin for MS?

😕 2

❓ 6

Thanabodee Charoenpiriyakij

05/31/2022, 11:10 AM

Hi, all I’ve a java rpc library that take data as Map<String, Obect> and return as the same type. I try to convert it to data class to make code readable. I’m finding a solution to serialize a map to object and deserialize it. Currently I found that we can use json convert object to the json and deserialize to map. But it quite a bit tricky. 🫥 I also found that kotlinx serialization has properties data serialization but the limitation is it convert nested object to flat key. 😢 Does anyone found this similar issue? How do you solve it?

Iwan Aucamp

06/02/2022, 3:31 PM

Which is a better choice for kotlin, quarkus or micronaut?

:ktor: 10

kenkyee

06/02/2022, 3:41 PM

FWIW, I found reactive support a bit quirky w/ Quarkus/Hibernate/Panache...feels like hibernate reactive isn't really there yet.

Andromadus Naruto

06/07/2022, 5:27 AM

Hi @everyone. I'm using the Komapper ORM for Kotlin and I can't seem to find a way to configure unique columns on a field via annotations. Can anyone with experience please help me with this? Thanks.

dleuck

06/08/2022, 5:26 AM

@Toshihiro Nakamura Are you using Komapper in any apps running in production? I really like the design of it, but I'm wondering if its been battle tested. We would be using it with Ktor and Postgres.

Andrzej Sawoniewicz

06/09/2022, 2:56 PM

Hi, anybody know why using @Validated on a Controller class in Spring could mess up with constructor injections? I simply get null values for all injected objects. The problem came out after migration to Kotlin from Java.

:not-kotlin: 4

Gopal S Akshintala

06/14/2022, 1:46 PM

Tech stack question: Does anyone know of examples of using Ktor for distributed systems? I am looking to implement asynchronous parallel processing, evaluating if Ktor is a right framework to start. I recently explored Spring batch which seems close to what I need, are there any similar use-cases solved with Ktor?

Cody Mikol

06/14/2022, 6:30 PM

how do you enable the k2 compiler in gradle (groovy)?

Paul-Arthur Thiery

06/15/2022, 1:35 PM

Hi ! I've checked the docs for compiling Java and Kotlin together with Maven, and I've scrupulously copied the pom.xml setup, however I'm still get

Unresolved Reference

for every single import in my

.kt

files. Using the builtin Intellij compiler works fine however ! Is this a known issue ?

IsaacMart

06/17/2022, 4:51 AM

Hello guys, Am using ktor and mongoDB as my backend for an android project. When inserting a document, the acknowledgement returns true, but when i get InsertedId, it returns null despite being inserted in the database

:not-kotlin: 4

🚔 1

Partho Paul

06/21/2022, 5:13 AM

Hi everyone, I’m using ktor and dynamodb for my backend project. I’m trying to fetch data from db using the below piece of code:

getDynamoDbClient().use { ddb ->
                return@use ddb.getItem(dbRequest)
            }

Upon running this, I’m getting

java.lang.IncompatibleClassChangeError: Found interface kotlin.time.TimeMark, but class was expected

error. I’m doing it as it’s shown in https://github.com/awsdocs/aws-doc-sdk-examples/blob/main/kotlin/services/dynamodb/src/main/kotlin/com/kotlin/dynamodb/GetItem.kt. Am I doing anything wrong? Kotlin version: 1.7.0, Ktor version: 2.0.2, aws version: 0.16.0 TIA

👀 2

itzik kasovitch

06/27/2022, 8:14 AM

Hi, In my application that is running on top of Ktor 1.6.4 I noticed that call.receiveText() returns a garbled string if the input text is in Japanese. I ruled out that it happens on the client side. Is there some configuration I forgot to do to make receiveText handle Japanese correctly?

v79

06/27/2022, 8:10 PM

Would there be much interest in a #serverless channel? I've often wondered if Ktor could compile to Javascript to run on AWS Lambda...

:yes: 2

Alex Stelmachonak

06/28/2022, 3:35 PM

Hi all! Want to collect some ideas about the problem I have in Kotlin+Jackson space. I wanted to implement something like this:

interface HttpResponseBody {
	val asString: String
	
	inline fun <reified T : Any> asInstanceOf(format: BodyFormat): T =
        when (format) {
            BodyFormat.JSON -> jacksonObjectMapper().readValue(asString)
        }
}

so I can utilize the jackson-kotlin support of reified type parameters to not pass class instance to the deserialization method and be able to use it like this

response.body.asInstanceOf<User>(BodyFormat.JSON)

But

reified

only works in

inline

functions and I can't inline the function in interface. I was looking for not ugly way to workaround that and have similar implementation in place. So far I found two ways of doing this: 1. Convert

HttpResponseBody

to abstract class, so

inline

and

reified

are working. 2. Convert

asInstanceOf

method to the extension method of the

HttpResponseBody

interface. Both are working, but doesn't fit nicely with my other codebase (which I probably need to refactor), but I wanted to ask may be I am missing some other solutions?

Title

Alex Stelmachonak

06/28/2022, 3:35 PM

Hi all! Want to collect some ideas about the problem I have in Kotlin+Jackson space. I wanted to implement something like this:

interface HttpResponseBody {
	val asString: String
	
	inline fun <reified T : Any> asInstanceOf(format: BodyFormat): T =
        when (format) {
            BodyFormat.JSON -> jacksonObjectMapper().readValue(asString)
        }
}

so I can utilize the jackson-kotlin support of reified type parameters to not pass class instance to the deserialization method and be able to use it like this

response.body.asInstanceOf<User>(BodyFormat.JSON)

But

reified

only works in

inline

functions and I can't inline the function in interface. I was looking for not ugly way to workaround that and have similar implementation in place. So far I found two ways of doing this: 1. Convert

HttpResponseBody

to abstract class, so

inline

and

reified

are working. 2. Convert

asInstanceOf

method to the extension method of the

HttpResponseBody

interface. Both are working, but doesn't fit nicely with my other codebase (which I probably need to refactor), but I wanted to ask may be I am missing some other solutions?

mitch

06/28/2022, 9:50 PM

Hey @Alex Stelmachonak I'm curious of what others do as well but what I usually do is to define a non-inline function in the interface, and then declare an inline extension function on the interface. Something like this:

interface HttpResponseBody {
  fun <T> instanceOf(bodyFormat: BodyFormat, clazz: Class<T>): T
}

inline fun <reified T> HttpResponseBody.instanceOf(bodyFormat: BodyFormat) = instanceOf(bodyFormat, T::class.java)

Oh you had tried this already in your second approach.

Alex Stelmachonak

06/28/2022, 9:57 PM

Thanks! The issue here is that I can't just call method from interface from the extension function - jackson kotlin method

readValue

requires generic type to be

reified

, which is not possible. If I just do

T::class.java

it kind of works, but looses the benefits of Kotlin classes additional runtime data. I.e. I can't just use data class without extra

@JsonProperty

annotations.

I will put this aside for some time and will try to fix it in few days - want to have a fresh look at this

DALDEI

07/02/2022, 8:26 AM

use the same type function that jackson-kotlin uses, not T::class.java use instanceOf( bodyFormat , jacksonTypeRef<T>() )

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