The Spring Framework and especially Spring Boot, are very popular and widely used for programming applications in Java. For Scala, there are other popular frameworks, particularly for programming web servers, such as the Play Framework.

In this small series of articles, we want to explore whether and to what extent we can program functionally in Scala while still using Spring Boot.

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This is an English translation of the German version of this post.

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Software must be configurable to be flexible. A configuration defines parameters and settings for software. Usually, the settings are stored in a configuration file that the software reads. But how do we ensure that a configuration is complete and valid? That all aspects that need to be configured are actually configured? That there are sensible defaults for values not explicitly configured? And that the values entered in the configuration are actually sensible values?

To avoid answering these questions anew for each project, we have developed a library for configurations for Clojure and ClojureScript that we have been using successfully for many years - and present in this article.

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This post is part of the series on functional software architecture in Kotlin. The first one covered functional validation, and this part is about monads. In Kotlin, these are particularly useful when describing domain workflows that should be separated from the technical logic for executing these workflows - specifically using small domain-specific languages (DSLs).

This episode is about how monads actually work. Kotlin has - like many functional languages - special syntax for this, even though you won‘t find it under the „M-word“ in the documentation. It‘s hidden behind the suspend keyword.

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Lenses are an important concept in functional programming with great practical utility. Several years ago, we already introduced functional lenses here on the blog. Since then, we have continuously expanded our use of lenses in our daily work. Today we want to show how we use lenses as bidirectional transformations and how they help us convert between data representations.

We implement the example for this article with our comprehensive and freely available Clojure library called Active Clojure, which we use in all our Clojure projects. This library includes implementations of lenses and Records, the latter of which is for representing compound data in Clojure. The combination of lenses and records is particularly helpful.

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