A Java geek

Write extension functions for your own classes in Kotlin

A recent question on Kotlin’s Reddit came to my attention lately: 'Why is it bad to write extension functions for classes that you own?' One of the answer was that it was the opposite: it’s a good practice, and for several reasons. Among them were two very important ones that improve the design of one’s code: Able to call the function on a nullable. For a class with generic types, add a function that is only available when a specific type is used.

Technical

There's no such thing as CI/CD!

Recently, I became aware of a trend that has been growing since too long: conflating CI and CD into the same word group - CI/CD. When this is done by marketers, this is business as usual, a mix of buzzwords and hype that shouts 'Look at me!'. But when this is repeated by professional software engineers, I start to worry. And this is exactly what’s happening right now.

Development

Composition over inheritance applied to Docker

This post is neither a recommendation, nor even a suggestion. It’s just me toying with an idea: Implement it at your own risk! The main benefit of Docker containers is that they are self-contained. For developers, that means one just needs to inherit from the desired Docker image that contains the necessary required dependencies, and presto, one can build one’s application deliver it to production. Most of the times, the process is pretty straightforward.

JavaEE

Easier attribute management in Java EE

Last year, I’ve been tasked to design a course and teach it to students of the 3rd year of a higher-education school in Geneva. Though I’m a Spring fan, foundations of Spring’s Web MVC take their root in Java EE e.g. servlets and filters. For this reason, I created the course on Java EE. I started my career with Java and J2EE 1.3. By reading the documentation again, I learned a few things regarding the changes since that time.

Development

Kotlin operators

Consider 2 types X and Y, and a function f defined as: class X, class Y and val f = { _:X → Y() }. In Kotlin, it’s possible to call the function f with a parameter of type X using invoke(): fun f(x: X) = Y() val y: Y = f.invoke(X()). The following calls the function f with a parameter of type X using invoke().

Development

What's the version of my Jekyll site?

A couple of years ago, I wrote how one could check the version of one’s deployed application. Recent technologies such as Spring Boot makes it even easier. It’s as important for regular applications as for static sites such as Jekyll. I wanted to have this blog display some basic Git data. As I publish from the tip of master and not from tags, the data I want is the commit hash.

Miscellaneous

Advices for junior conference speakers

Some years ago, I started my journey on the conference circuit. I did that on my own, in my free time. Without mentorship on how to do that, and with my gut feeling as the only guidance, I made plenty of mistakes… and I still regularly do. However, I now have a couple of hard-earned experience years behind me. Note that conferences are IMHO just a subset of public speaking in general. Meetups are another form, with a different set of constraints and challenges.

Java

Migrating the ServiceLoader to the Java 9 module system

A long long (long?) time ago, I wrote a post about the ServiceLoader. In short, the Service Loader allows to separate an API and its implementations in different JARs. The client code depends on the API only, while at runtime, the implementation(s) that is (are) on the classpath will be used. This is great way to decouple the client code from the implementing one.

Development

ONBUILD, the overlooked Docker directive

It’s hard to ignore Docker nowadays. There are a lot of blog posts available on the Web. The problem is that most always repeat the same. In this post, I’d like to focus on one directive that I find overlooked via a use-case: it is Java specific, but the parallel can be easily drawn to other tech stacks. The problem The situation is the following: as a developer, I’d like to use Docker as a way to package a JAR from the sources of my application.

Nicolas Fränkel's blog