Find me on Medium It has been a while since I posted on this blog. There are multiple reasons for this but mainly I just didn't have the time and motivation to continue blogging here. I have to be honest: The ROI was never really worth the effort, unfortunately. I am still super happy about the things I learned along the way and I'm happy to say that over 500k people visited my blog since I started it. I don't plan to kill it either, although I sometimes considered it as I don't like the fact that some articles are outdated and would actually need a rework. If you read articles on this blog, b ..read more

Serverless Kotlin on OpenFaaS With this article, my goal is to demonstrate how Serverless Kotlin can look like by introducing you to one of the coolest Serverless platforms: OpenFaaS. OpenFaaS is an open-source, community-owned project that you may use to run your functions and microservices on any public or private cloud. You can run your Docker image on OpenFaaS, which runs and scales it for you. As a result, you are free to choose any programming language as long as it can be packaged into a Docker image. Throughout this post, we want to learn about the concepts behind Serverless and Functi ..read more

Server as a function with Kotlin - http4k Have you ever heard about the concept of "Server as a Function"? The idea is that we write our server application based on just ordinary functions, which is based on a concept outlined in the paper Your Server as a Function written and published by Twitter/Marius Eriksen. In the Kotlin world, the most prominent implementation of this concept is http4k, which the maintainers describe as an "HTTP toolset written in Kotlin with a focus on creating simple, testable APIs". The best part about it is that http4k applications are just Kotlin functions that we ..read more

Does Kotlin have a default Map? Have you ever used a default map or default dict before? If you know Python a bit, you probably saw its defaultdict in action at some point. Kotlin also comes with a similar tool which I want to demonstrate in this little article. You can find the Python defaultdict documentation and some examples here but the basic use case is shown in the following snippet: from collections import defaultdict d = defaultdict(int) print(d["someKey"]) //0 The defaultdict can also be used with other types and makes sure that you don't get a KeyError when running your code. I ..read more

Diving into advanced Kotlin features (Devoxx UK 2019) This year I gave my first "big conference" talk at Devoxx UK 2019 in London speaking about advanced Kotlin features. I targeted this talk towards an audience with intermediate Kotlin skills. Therefore I assumed that most of the standard language features, e.g., extension functions, class definitions, properties, and so on were familiar already, so I didn't explain everything during the session. The advanced Kotlin features I covered are listed next: Infix Functions Operator Overloading Higher Order Functions and Inling Lambdas with Receive ..read more

Kotlin Inline Classes - How they work and when you should use them Kotlin introduced inline classes with version 1.3 as an experimental feature. You should be aware that their implementation can still change in future releases, but it's already a great time to learn about them now. Inline classes add a simple tool we can use to wrap some other type without adding runtime overhead through additional heap allocations. In this article, we want to see how inline classes in Kotlin work and when it makes sense to use them. Enable inline classes in your project To enable inline classes in your projec ..read more

How Kotlin makes me a more productive software developer I've been writing JVM code for more than seven years now, and I did so mainly using Java. This changed about two years ago when I picked up Kotlin. By now, I managed to drop the Java language more-or-less entirely in favor of Kotlin. I did this because I feel much more productive with the language. It lets me focus more on the business logic rather than forcing me to write boilerplate code over and over again. In this post, I tell you how Kotlin makes me a more productive developer. I certainly know Kotlin much better than I ever knew Ja ..read more

On Kotlin Coroutines and how concurrency is different from parallelism The official docs describe Kotlin Coroutines as a tool "for asynchronous programming and more", especially are coroutines supposed to support us with "asynchronous or non-blocking programming". What exactly does this mean? How is "asynchrony" related to the terms "concurrency" and "parallelism", tags we hear about a lot in this context as well. In this article, we will see that coroutines are mostly concerned about concurrency and not primarily about parallelism. Coroutines provide sophisticated means which help us structur ..read more

Hibernate with Kotlin - powered by Spring Boot In this post, I'd like to demonstrate what you need to consider when using Hibernate with Kotlin. Hibernate is probably the most famous framework for object-relational mapping (ORM) on the JVM, which is used to persistently store Plain Old Java Objects (POJOs) in relational databases. It also implements the Java Persistence API, a specification that "describes the management of relational data" on the JVM. Summary (TL;DR) Put the kotlin-noarg compiler plugin on your build path, it will generate no-argument constructors for your Hibernate entities ..read more

Organize Kotlin Scripts as Gradle tasks In this article, you will learn how you can organize multiple Kotlin scripts as Gradle tasks and make them easily executable this way. I've found a discussion about this here. Somebody wanted to execute Kotlin scripts with Gradle build scripts which is, of course, possible by using kotlinc as shown in this (Groovy) build script. This doesn't look very pretty though, and, as described in the corresponding thread, isn't very performant and manageable. Another solution would be to use Gradle scripts written with the Kotlin DSL and define custom tasks within ..read more