I spent a few weeks working on performance improvements for a Kotlin server-side framework and folks here might find it interesting to look at (GitHub repo linked in the tweet) https://twitter.com/CarrotCodes/status/1541902976733876224 🙂

Hello, documentation recommends using

<http://0.0.0.0:8080>

, but after starting the server, this address doesn't work.

<http://localhost:8080>

works, tho. Why is it so ?

Hi, I have a field named: isPrivatePerson: Boolean? in my data class. The JDBI has a problem with it because it cannot find the getter starting with "get". Is there any solution for that besides adding the separated getter and setter manualy?

For a purpose of using MapStruct (mapping library) I need to annotate the default constructor. As I want to use vals in that class I want to annotate the constructor with all fields. I can of course use @JvmOverloads to get all variations but how could I annotate the one with all fields? data class ClassName @JvmOverloads @Default constructor(... - does not work

Hello, I’m trying to make a unit test for a java service which uses a client written in kotlin. The client may throw a checked exception but since there are no checked exceptions in kotlin when calling the method from java it doesn’t force me to wrap it into a try..catch. When I’m trying to mock the method with Mockito it says I cannot throw a checked exception

Checked exception is invalid for this method!

The only ways I would be able to make the test is either rewrite the client method in java and mark it with checked exception or wrap the call and rethrow a runtime exception right? (any other ideias?)

Can anyone suggest me a caching library for ktor server?

Hello! Good docs is an asset, so we are constantly trying to improve 🙂 I’m working on improving the Spring/Kotlin tutorial in the docs and would love to hear some feedback.

When is the correct time to call AsynchronousSocketChannel::close() ? If I call it directly after calling write, I'm running into a connection reset error in the browser (I'm experimenting with HTTP servers) https://stackoverflow.com/questions/72903847/connection-reset-error-when-closing-asynchronoussocketchannel

if you use write that returns a Future and call close when Future isDone

Hello, I am using Spring Boot 2.7.1/Kotlin 1.6.20/Java 17 in the current project, and encountered the famous java module export package issues, but I added

@file:Suppress("JAVA_MODULE_DOES_NOT_EXPORT_PACKAGE")

at the first line of the Kotlin file, it did not resolve my issues. I have tried to recompile the whole project.

Any suggestion here>

Hi everyone, I'm noob kotlin dev, try to use kotlin with spring boot

I have an issue with association suppose I have Post entity with OnetoMany Tag entity

I want to have add more tags to the post by this way

post.tags.add(existedTag)
postRepo.save(post)

but It didn't work

Hello! I am trying to make rpc calls to a service i haven't written myself. The issue is, it uses messagepack to encode data. If they were using protobuff i would be ok with just using the java implementation of gRPC but it is not making it easy for me to switch the serialization method. Are there any kotlin libraries for rpc calls that would be easier to use for this purpose?

Hello! Quick question for Kotlin users with Spring.. When you are using constructor injection with spring do you keep the constructor classes as nullable or not nullable? for example;

@Service
class FirestoreService(
  private val firestore: Firestore?,
)

vs.

@Service
class FirestoreService(
  private val firestore: Firestore,
)

Non-nullable unless you have a good reason for it to be nullable

thanks! technically it can fail to initialize but i think spring will throw an error before code reaches the reference to the instance

off-hand, i can't think of a good reason for a constructor param to be nullable 😐

Hello everyone. I have this docker db instance script :

version: '3.7'
services:

  #MySQL Service
  db:
    image: mysql:5.7.22
    container_name: ${DOCKER_CONTAINER_NAME_SLUG}_db
    restart: unless-stopped
    tty: true
    ports:
      - ${DOCKER_MYSQL_PORTS}
    environment:
      MYSQL_ROOT_PASSWORD: ${DB_PASSWORD}
      MYSQL_DATABASE: ${DB_DATABASE}
      MYSQL_USER: ${DB_USERNAME}
      MYSQL_PASSWORD: ${DB_PASSWORD}
      SERVICE_TAGS: dev
      SERVICE_NAME: mysql
    volumes:
      - dbdata:/var/lib/mysql/
      - ./mysql/my.cnf:/etc/mysql/my.cnf
    networks:
      - my-network

#Docker Networks
networks:
  my-network:
    driver: bridge

#Volumes
volumes:
  dbdata:
    driver: local

then in a different spring boot project, I have this docker-compose file:

version: '3'

services:
  app:
    container_name: api-app
    build:
      context: .
      dockerfile: Dockerfile
    ports:
      - "8080:8080"

networks:
  default:
    external:
      name: my-network

it fails to build because I get this error:

java.sql.SQLNonTransientConnectionException: Could not create connection to database server. Attempted reconnect 3 times. Giving up.

Anyone see the problem ?

I am sure this is one of those topics with no definite answers but how do you all think about throwing exceptions in kotlin while working with spring? Roman Elizov has a great blog post on how to use exceptions with Kotlin. He emphasizes that catching exceptions in kotlin is usually code smell. But does that mean that I should be able to throw exceptions freely in my Spring application if I am using application level exception handlers? More specifically let's say I have function that looks up an item in the database, and a controller that calls this service. If the item is not in the database, should I return a nullable from the service or should I throw an exception?

Another round of TechEmpower Web Frameworks Benchmark was released: https://www.techempower.com/benchmarks/#section=data-r21

I get stuck on

com.zaxxer.hikari.HikariDataSource: HikariPool-1 - Starting...

every single time I run my application. Using Spring Boot and Docker Compose on Arch Linux. What I've tried: • Rebooting • Checking the connection string • Checking database availability • Checking my docker compose configuration • Downgrading the kernel then rebooting • Upgrading the kernel then rebooting • Cleaning up docker (containers, images, volumes ....) then rebooting • Restarting docker Also, I use Spring Boot 2.7.1, PostgreSQL 15beta2-bullseye, Docker 20.10.17 and Docker Compose 2.6.1

I added the environment variables but still can't deploy to heroku . I don't know what the problem

This message was deleted.

Hey folks, I'm looking into data classes and I wanted to verify that

copy

creates shallow, not deep copies. The math checks out for complex types such as lists or other data classes, but not for 'primitives' likes Strings and Enums. Can someone help me clarify this? [Here is a complete example](https://pl.kotl.in/CzsYyKC_l) , but in essence for the given code, I would potentially expect

name

to also be mutated in the copy if data classes were purely shallow. Am I getting this wrong?

import java.util.*

enum class WEAPONS{
    AXE, SWORD, WAND, BOW
}

enum class CLASS{
    WIZARD, WARRIOR, PALADIN, THIEF
}

data class Origin(val city: String, var country: String)

data class FantasyHero(var name: String, val weapons: MutableList<WEAPONS>, var heroClass: CLASS?, val origin: Origin = Origin("Utrecht", "The Netherlands"))

fun main(){
    val gandalf = FantasyHero("Gandalf the Grey", mutableListOf(WEAPONS.WAND), CLASS.WIZARD)
    val anotherGandalf = FantasyHero("Gandalf the Grey", mutableListOf(WEAPONS.WAND), CLASS.WIZARD)
    val gandalfCopy = gandalf.copy()
    val betterGandalf = gandalf.copy(name="Gandalf the White")

    println("--------")
    println("Changing the first instance's name")


    gandalf.name = "Gandalf the White"
    println(gandalf.name)
    println(anotherGandalf.name)
    println(gandalfCopy.name)
    println(betterGandalf.name)

    println("--------")
    println("Changing the first instance's class")

    gandalf.heroClass = CLASS.PALADIN
    println(gandalf.heroClass)
    println(anotherGandalf.heroClass)
    println(gandalfCopy.heroClass)
    println(betterGandalf.heroClass)
}

--------
Changing the first instance's name
Gandalf the White
Gandalf the Grey
Gandalf the Grey
Gandalf the White
--------
Changing the first instance's class
PALADIN
WIZARD
WIZARD
WIZARD

[The documentation of data class](https://kotlinlang.org/docs/data-classes.html#copying) does imply clearly that copies are shallow. The implementation of this function for the

User

class above would be as follows:

fun copy(name: String = this.name, age: Int = this.age) = User(name, age)

Off-topic: https://engineering.fb.com/2022/07/27/developer-tools/programming-languages-endorsed-for-server-side-use-at-meta/

Any one knows why it is throwing io exception when i connect websocket route in ktor .. iam using javascript to connect the route ws://localhost:8080/user/userId .. when i connect io exception throws on intellj idea log.. if i use ws://localhost:8080/member/userId .. this will work fine. I dont know why the first link is not working

Are Kotlin DSLs (typesafe builders) only for use internally by application developers? Want to create and expose a DSL for "power" end-users to define some complex objects that are currently quite tedious via a point-and-click UI, but think this is not possible. Allowing them to define via JSON/YAML is an option but the DSL format is even easier to use and validate.