Hands-on Examples on Advanced Beginner

Environment Setup Deep Dive

d8lzz1gpw@mozmail.com (kimbenji) — Wed, 13 May 2026 00:00:00 +0000

Estimated time: about 10 minutes

TL;DR

Understand the meaning of the core blocks in build.gradle.kts (plugins, dependencies, kotlin, application)

Difference between jvmToolchain(17) and sourceCompatibility

Tune the collaboration environment with IntelliJ IDEA shortcuts and ktlint integration

Troubleshooting patterns (class version, dependency refresh, cache invalidation)

Target audience: Developers who have finished the basics of Kotlin environment setup Prerequisites: Quick Start completed (JDK 17 installation, gradle init, first ./gradlew run)

Basic installation is in Quick Start
First-time setup such as JDK 17 installation, creating a Kotlin DSL project with gradle init, and opening IntelliJ IDEA is covered in Quick Start. This page goes one step further — summarizing the core build script options and additional settings useful for collaboration.

Step 1 — Core build.gradle.kts Settings#

This is a build script written in Kotlin DSL. Let’s understand the key options.

Basic Examples

d8lzz1gpw@mozmail.com (kimbenji) — Wed, 13 May 2026 00:00:00 +0000

Estimated time: about 15 minutes

TL;DR

Define concise data models with data class

Use collection functions like filter, map, sortedBy

Add domain-specific behavior to existing types via extension functions

Make active use of Kotlin expressions like when, ?:, ?.

Target audience: Developers who have completed Kotlin environment setup Prerequisites: Environment Setup

Run Kotlin’s core features directly in your installed environment. Each example creates a file under src/main/kotlin/ and runs it.

Spring Boot Integration

d8lzz1gpw@mozmail.com (kimbenji) — Wed, 13 May 2026 00:00:00 +0000

Estimated time: about 20 minutes

TL;DR

Select Kotlin + Spring Web + Spring Data JPA on start.spring.io

kotlin-spring and kotlin-jpa plugins are essential in build.gradle.kts

The JPA entity open class issue → resolved automatically by the kotlin-jpa plugin

You can write @RestController, @Service, @Entity in Kotlin style

Target audience: Developers with Kotlin basics and Spring Boot experience Prerequisites: Environment Setup, Spring Boot basics

Build a simple user-management REST API by integrating Kotlin with Spring Boot 3.2.x.

Kafka Integration

d8lzz1gpw@mozmail.com (kimbenji) — Wed, 13 May 2026 00:00:00 +0000

Estimated time: about 25 minutes

TL;DR

Add the spring-kafka dependency and configure application.yml

Publish messages with KafkaTemplate<String, String>

Receive messages with @KafkaListener(topics = ["..."], groupId = "...")

Consumer Group naming convention: {app-name}-group

Target audience: Developers familiar with Kotlin + Spring Boot basics Prerequisites: Spring Boot Integration, Kafka basics

Implement an example that publishes and receives messages using Kotlin and Spring Kafka. This example uses the Kafka instance (KRaft mode, port 9092) in the site’s docker/ directory.

Practical Coroutines

d8lzz1gpw@mozmail.com (kimbenji) — Wed, 13 May 2026 00:00:00 +0000

Estimated time: about 30 minutes

TL;DR

async { } + await() — call two APIs in parallel, faster than serial

Using suspend fun on @GetMapping enables coroutine controllers in Spring MVC

withTimeout(ms) { } — set a timeout; on exceed throws TimeoutCancellationException

Structured concurrency — when the parent coroutine is cancelled, child coroutines are also cancelled automatically

Target audience: Developers with Kotlin basics and Spring Boot experience Prerequisites: Spring Boot Integration, basic coroutine concepts

Multiplatform Intro

d8lzz1gpw@mozmail.com (kimbenji) — Wed, 13 May 2026 00:00:00 +0000

Estimated time: about 30 minutes

TL;DR

commonMain — Kotlin code shared across all platforms

expect — declared in the common module; actual — implemented per platform

jvmMain, jsMain — platform-specific code

Reuse business logic written once on JVM (backend/Android) and JS (frontend)

Target audience: Intermediate or above Kotlin developers Prerequisites: Environment Setup, basic Kotlin syntax

Use Kotlin Multiplatform (KMP) to share business logic across multiple platforms. We’ll write a date formatter as a common module and implement it for both JVM and JS in a mini project.