Shameless plug. I’m starting a series on youtube on Quarkus in Kotlin. I’d appreciate any comments in the comment section if you have suggestions:

I am using ktor with ContentNegotiation. What is the idiomatic way to handle the unchecked exceptions you can get when retrieving a response using ktor client? example code

val responseData: ReservedCitizenResponse = response.body()

. If there is something wrong in the response body this will just crash with an JsonDecodingException as an unchecked exception. It would be nice if the .body() function returned a Result monad so you could handle the cases of successful and unsuccessful serialization.

Question regarding logging, in the context of a Spring project, using SLF4J, Coroutines and Datadog, asking here to see if someone else has encountered this before. When logging our uncaught exceptions in normal non-coroutine code, the exception is logged by slf4j. The logs are picked up by a Datadog agent, and sent to Datadog. When the exception is shown in Datadog, it takes up one line in the logger, with the stacktrace placed in the log entry’s details. We recently added coroutines to this service, defining an

ApplicationScope

like

class ApplicationScope(applicationScope: CoroutineScope) : CoroutineScope by applicationScope
// Then provided like
@Bean
fun applicationScope(): ApplicationScope {
  return ApplicationScope(CoroutineScope(SupervisorJob() + <http://Dispatchers.IO|Dispatchers.IO>))
}

then converted an existing function to be fire-and-forget by using `launch`:

fun doSomething(...) = applicationScope.launch {...}

When an unhandled exception is thrown in the coroutine, somehow it doesn’t follow the normal logging/formatting process. Instead of a single error line in the log, we get each line in the stacktrace showing up as a separate line in the logs. This then shows up in the timeline as a whole lot of errors (50-100+) occurring at the same time. Has someone who uses this combination of coroutines-slf4j-datadog experienced this before? Could it be that the logger is not picking up these unhandled exceptions and it’s logging to the console? Or maybe we need to add something special to the

ApplicationScope

to get SLF4J/Datadog to parse/format this error properly?

Hello, I'm very noob for android development can anyone please tell me how to implement real api with @post method in my android studio with kotlin project.

hi, folks! I have a question about

is

checks and delegation from a class to an object. Ktor has an extension function on

ApplicationRequest

that uses

when(this)

to check if the request

is

a

ServletApplicationRequest

. The problem is that the actual request object that I call the extension function on, is a

RoutingApplicationRequest

, which is a class that delegates to the original request object. Which in turn causes

is ServletApplicationRequest

to be false, as

is

only seems to check class inheritance hierarchies, and not delegation. Is there a way to work around this? Or is it an issue/bug that Ktor needs to handle differently to work as expected? FYI, here’s the full extension function:

public val ApplicationRequest.javaSecurityPrincipal: Principal?
    get() = when (this) {
        is ServletApplicationRequest -> servletRequest.userPrincipal
        else -> null
    }

and here’s the class that the instance of the request object is a member of:

public class RoutingApplicationRequest(
    override val call: RoutingApplicationCall,
    override val pipeline: ApplicationReceivePipeline,
    request: ApplicationRequest
) : ApplicationRequest by request

Does @JvmRecord give any performance benetfits? For example around heap footprint, object equality/hashcode etc?

Hello all!

This message was deleted.

How can we read config data into code from custom properties file and assigning this values in application.conf?

Please assist me. I'm receiving a parsing error when I try to read from application.conf into the code.

Error - Property 'ktor.database.url' not found and throwing applicationconfigurationexception

Hello guys! looking for tips and tricks for using kotlin native/JVM on AArch64 for backend systems/microservices

Looking for suggestions on Coroutines book for server side applications (Non-Android platform). Any book which you would recommend here. thanks..

hello i work on spring boot app using Kotlin lang if the HTTP method is GET and i request the endpoint with POST method it throw server error, so how to catch this error and throw runtime error instead. thank's

Hi. I am new to Ktor and I have a problem. My problem is that items in database have a numeric id that needs to be increase by one each request. Right now if I receive 2 or more requests at the same time they query the same last item from database having the same item. I need to wait until the first request is completed before accepting a new one, so I can keep the correct order in the database. Something like a request queue or Channel or similar. So, my question is. How can I make the pipeline sequencial? and wait until it is completed before starting a new one?

Cross-posting this here in case you folks have some insight 🙂 https://kotlinlang.slack.com/archives/C1CFAFJSK/p1663212895400299

Hey Hellu! Thank you so much for accepting me. I am pretty new at Kotlin and is working with a ktor-app right now. I have not built it from the beginning but I have the main responsibility of the application. We have some tests in the application but I wanted to higher the test-coverage by using externalServices but the problem is that I get DuplicatePluginException on io.ktor.server.plugins.contentnegotiation.ContentNegotiation because both the mock-server and my application uses the same plugin. I have tried everything I can think of and that the internet provided to me but nothing works. Can someone please help me, have som kotlin-experts in the team but they are also out of ideas :-(

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I’m having a bit of trouble with the type system. Anyone able to help me resolve this? The idea is that the type defined by the variable

e

in the

main()

function determines the return type of the

dispatch()

function. The error I’m getting is:

Type mismatch.
Required:
  Result<E>
Found:
  Result<ExampleEvent>

Hello, what is the best practice to implement assertions in unittests written in kotlin? JUnit's built-in Assertions? AssertJ? Hamcrest? Kotest?

I would like to retrieve response body message for a given 400 status code when using the spring webclient. However, I can only find the error code and not the actual error message contained in the code. I am using following snippet. how to actually extract the response body in the 400 status response .

val retrievedResource: Mono<String> = myRequest
            .retrieve()
            .onStatus(HttpStatus::is4xxClientError) { Mono.error(RuntimeException("4XX Error ${it.statusCode()}, ${it.bodyToMono(String::class.java)}")) }
            .onStatus(HttpStatus::is5xxServerError) { Mono.error(RuntimeException("5XX Error ${it.statusCode()}, ${it.bodyToMono(String::class.java)}")) }
        .bodyToMono(String::class.java)
        return retrievedResource.share().block()

Hey people!, Anyone knows how to get an SQL connection to PostgresSQL via Kotlin Native? I'm scrambling to get this done and I'm, already looking at the possibility of calling postgress command natively by making my own library, but maybe I'm just missing some easier solution?

Please Simple Question: where is the code stored after jvm work and loaded the needed classes, are the instruction set in the stack or where?

Hello friends, Do anyone know how can I load file which is there in resource folder in ktor?

hey everyone. Got a question about the better implementation of the function, maybe someone could assist. I have a function that should return different Response based on the received data from the

workflowService.findByCompanyId

, that returns data class:

data class WorkflowWithStatusLookup(val workflow: Workflow, val status: Result<WorkflowStatus>)

also, I’d like to log the exception based on the “invalid” result of the status. Here is want I’ve came up with, but I’m pretty sure it’s not optimal way

override fun listWorkflow(featureToggles: FeatureToggles): ResponseEntity<GetWorkflowsResponse> {
        return runBlocking(requestContext.coroutineContext) {
            val (valid, invalid) = workflowService.findByCompanyId(getCompanyId(), featureToggles)
                .partition { it.status.isSuccess }
            val apiResponseModel = valid.map {
                it.workflow.toWorkflowInfoResponse(it.status.getOrThrow())
            }
            return@runBlocking if (invalid.isEmpty()) {
                ResponseEntity(
                    GetWorkflowsResponse(
                        data = apiResponseModel
                    ),
                    HttpStatus.OK
                )
            } else {
                ResponseEntity(
                    GetWorkflowsResponse(
                        data = apiResponseModel,
                        meta = invalid.map { it.workflow.name }
                    ),
                    HttpStatus.PARTIAL_CONTENT
                ).also {
                    invalid.forEach {
                        throw FormNotFound(
                            it.workflow.definition.trigger.entityId!!.toString(),
                            it.workflow.companyId
                        )
                    }
                }
            }
        }
    }

For Realm Kotlin sdk, is there a simple way to serialize ObjectId? The ObjectId itself is an interface while the actual object to be serialized is ObjectIdImpl, so I always get the error

ObjectIdImpl is not registered for polymorphic serialization in the scope of ObjectId

when using a custom serializer

Hey people, in case you are curious how to use JOOQ with Spring, Arrow in a reactive way using coroutines, please take a look at my example repository at: https://github.com/sbuettner/reactive-database-access-kotlin Its very small and hopefully approachable repository with some documentation for people interested in this topic. Feedback appreciated.

Would it be possible / realistic to serialize and un-serialize an exception?

Hey all, I have a question about precompiled strings that I'd like to be able to use in annotations (so they must be

const val

and cannot be

val

). Does anybody have any suggestions? The test below fails right now, but I'd like to make it pass by only adding code. I'd love to use

.trimIndent()

when declaring

myString

but I can't. Is there something I can use that the compiler will unfold?

const val myString = """
    This is my string. I wrap it across multiple lines when it
    becomes too long, but there should be no lines visible when
    using this string. In other words, the newlines should be
    compiled out of this string, and the margin collapsed. Is
    there any compiler plugin I can use that can help make this
    a reality?
"""

class ExampleTest {
    @Test
    fun `precompiled multi-line string has no newlines`() {
        expectThat(myString).doesNotContain('/n')
    }
}