Development Tools

http4k – lightweight but fully-featured HTTP toolkit

http4k is a lightweight but fully-featured HTTP toolkit written in pure Kotlin that enables the serving and consuming of HTTP services in a functional and consistent way.

http4k applications are just Kotlin functions. An http4k server is just a regular function that gets invoked with a Request and returns a Response. In a single line of code you can switch your server between Java (built-in), Apache, Jetty, Netty, Undertow, Ktor, or Ratpack. An http4k client is just a regular function that you invoke with a Request and receives a Response. In a single line of code you can switch your client implementation between Java (built-in), Apache, Jetty, and OkHttp.

This is free and open source software.

Features include:

  • Tiny footprint – the core library has no dependencies and it’s all you need to create fully-functional applications. http4k APIs take advantage of Kotlin features and are powered by Functional Programming techniques.
  • Highly extendable – supports many Server, Serverless and HTTP Client technologies behind simple, consistent interfaces. http4k provides 50+ pre-built integrations for developers to choose from including Observability, JSON, and OpenAPI support.
  • Testability – create lightning fast, rock solid test suites for individual endpoints, applications or multi-service systems, all running fully in-memory. http4k embraces advanced testing approaches such as Approval, Chaos and Service Virtualization.
  • Battle-tested – takes advantage of technologies that have millions of hours of production runtime.

Support: GitHub Code Repository
Developer: David Denton, Ivan Sanchez and contributors
License: Apache License 2.0

http4k is written in Kotlin. Learn Kotlin with our recommended free books and free tutorials.

Return to Kotlin Web Frameworks

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