Server as a function with Kotlin – http4k

Server as a function with Kotlin – http4k

Functional Programming, Java, Kotlin, Software Development, Tutorial, Web
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 can test straightforwardly. Take a look at this first example: First http4k server example val app: HttpHandler = { request: Request -> Response(OK).body(request.body) } val server = app.asServer(SunHttp(8000)).start()…
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Coping with Kotlin’s Scope Functions: let, run, also, apply, with

Coping with Kotlin’s Scope Functions: let, run, also, apply, with

Functional Programming, Kotlin, Software Development
Coping with Kotlin's Scope Functions Functions in Kotlin are very important and it's much fun() to use them. One special collection of relevant functions can be described as "scope functions" and they are part of the Kotlin standard library: let, run, also, apply and with. You probably already heard about them and it's also likely that you even used some of them yet. Most people tend to have problems distinguishing all those functions, which is not very remarkable in view of the fact that their names may be a bit confusing. This post intends to demonstrate the differences between the available scope functions and also wants to discuss relevant use cases. Finally, an example will show how to apply scope functions and how they help to structure Kotlin code in…
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Create a DSL in Kotlin

Create a DSL in Kotlin

Functional Programming, Java, Kotlin, Software Development
Kotlin as a programming language provides some very powerful features, which allow the creation of custom internal Domain Specific Languages (DSL).  One of these features, I also wrote about on this blog, is called Function Literals with Receiver, others are the invoke convention or infix notation. In this article, I will show how to create a Kotlin DSL by introducing a library that exposes a DSL as its API. I've often been struggling with Java’s API when I had to set up SSL/TLS connections in scenarios where I e.g. needed to implement HTTPS communication. I always felt like wanting to write a little library that can support me with this task, hiding away all the difficulties and of course the boilerplate needed for it. (more…)
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Kotlin Operator Overloading – Working by Convention

Kotlin Operator Overloading – Working by Convention

Functional Programming, Kotlin, Software Development, Tutorial
Kotlin Operator Overloading and Conventions Introduction Kotlin supports a technique called conventions, everyone should be familiar with. For example, if you define a special method plus in your class, you can use the + operator by convention: Kotlin Operator Overloading. In this article, I want to show you which conventions you can use and I will also provide a few Kotlin code examples that demonstrate the concepts. (more…)
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Kotlin Function Literals with Receiver – Quick Introduction

Kotlin Function Literals with Receiver – Quick Introduction

Functional Programming, Kotlin, Software Development
Kotlin Function Literals with Receiver - The Foundation for DSLs and many Library Functions Today I want to give a quick introduction to Kotlin Function Literals with Receiver. This concept is what makes Kotlin great for designing Domain Specific Languages as we know it from Groovy for example. Also, Kotlin's standard library includes many functions which many of you have already used or at least seen probably: apply and with are the most prominent ones. (more…)
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