Kotlin
(22 posts)Backend development with Kotlin and Spring Boot — from REST APIs to event-driven architecture with Kafka. Real patterns from production systems.
All Posts
Kotlin 2.x — What Changed and How to Migrate
Everything you need to know about migrating to Kotlin 2.x — the K2 compiler, breaking changes, new features, Compose compiler integration, and step-by-step migration guide.
Kotlin Testing with Kotest & MockK — Beyond JUnit
Level up your Kotlin testing — Kotest for expressive test styles and assertions, MockK for idiomatic mocking. A practical guide with real-world examples.
Kotlin Value Classes & Inline Functions — Zero-Cost Abstractions
Learn how Kotlin value classes and inline functions give you type safety and abstraction without runtime overhead — wrapping primitives, type-safe IDs, and performance patterns.
Kotlin + Arrow — Functional Error Handling (Either, Raise)
Learn functional error handling in Kotlin with Arrow — Either, Raise, typed errors, and how to replace try-catch with composable error handling.
Kotlin Context Receivers & Scope Functions Deep Dive
Master Kotlin's scope functions (let, run, with, apply, also) and understand context receivers — when to use each, common patterns, and real-world examples.
Kotlin + Ktor — Building a REST API Without Spring
Build a REST API with Ktor 3 and Kotlin — routing, serialization, authentication, database access, and testing. A lightweight alternative to Spring Boot.
Kotlin Multiplatform — Share Code Between Android & Backend
A practical guide to Kotlin Multiplatform (KMP) — share business logic, models, and validation between your Android app and Spring Boot backend without duplicating code.
Kotlin DSL — Build Your Own Type-Safe Builder
Learn how to create type-safe DSLs in Kotlin using lambdas with receivers, extension functions, and builder patterns. Build a real HTML DSL and a config DSL from scratch.
Kotlin Sealed Classes & When Expressions — Modeling State
Learn how Kotlin sealed classes and when expressions work together to model state, handle API responses, and eliminate impossible states in your code.
Kotlin Flows — Cold Flows, Hot Flows & StateFlow Explained
Understand Kotlin Flow from the ground up — cold vs hot flows, Flow builders, operators, StateFlow, SharedFlow, and when to use each in Android and backend projects.
5 Kotlin Extension Functions You'll Use in Every Android Project
Practical Kotlin extension functions for Android — view visibility, toasts, keyboard handling, dp conversion, and intent helpers. Copy, paste, use.
Kotlin Coroutines — Part 3: Real-World Patterns
Flows, StateFlow, coroutines in Android and Spring Boot, Retrofit, Room, and testing — practical patterns you'll use every day.
Kotlin Coroutines — Part 2: Structured Concurrency
How structured concurrency keeps your coroutines under control — scopes, cancellation, exception handling, and the parent-child relationship that prevents orphan coroutines.
Kotlin Coroutines — Part 1: The Basics
A practical introduction to Kotlin coroutines — why they exist, how to launch them, suspend functions, dispatchers, and concurrent execution patterns.
JSON Parsing in Kotlin — Parsing with Kotlin Serialization
Parse a complex JSON response using Kotlin Serialization — the Kotlin-native, compile-time safe approach with no reflection.
XML Parsing in Kotlin — XmlPullParser and Retrofit
Parse XML in Kotlin using Android's built-in XmlPullParser and Retrofit with SimpleXML converter. Manual vs automatic — when to use what.
JSON Parsing in Kotlin — Which Library Should You Use?
A side-by-side comparison of org.json, Gson, Moshi, Kotlin Serialization, and Jackson for JSON parsing in Kotlin.
JSON Parsing in Kotlin — Parsing with Jackson
Parse a complex JSON response using Jackson with the Kotlin module — the server-side powerhouse that's also the default in Spring Boot.
JSON Parsing in Kotlin — Parsing with Moshi
Parse a complex JSON response using Moshi with Kotlin data classes, codegen, and proper null safety. The recommended JSON library for modern Android.
JSON Parsing in Kotlin — Parsing with Gson
Parse a complex JSON response using Gson with Kotlin data classes. Automatic mapping, @SerializedName, nullable types, and a custom TypeAdapter for Instant.
JSON Parsing in Kotlin — Manual Parsing with org.json
Parse a complex, real-world JSON response manually using org.json in Kotlin. Extension functions help, but the verbosity is still real.
Find and Delete Duplicate Files — Kotlin CLI Tool
A command-line utility in Kotlin that scans directories for duplicate files using MD5 hashing and lets you review and delete them safely.