http4k is an HTTP toolkit written in Kotlin that enables the serving and consuming of HTTP services in a functional and consistent way.
http4k applications are just Kotlin functions which can be mounted into a running backend.
The principles of http4k are:
- Application as a Function: Based on the Twitter paper "Your Server as a Function", all HTTP services can be composed of 2 types of simple function:
HttpHandler,Filter - Immutability: All entities in the library are immutable unless their function explicitly disallows this.
- Symmetric: The
HttpHandlerinterface is identical for both HTTP services and clients. This allows for simple offline testability of applications, as well as plugging together of services without HTTP container being required. - Dependency-lite: Apart the from Kotlin StdLib, http4k-core module has ZERO dependencies and weighs in at ~700kb. Add-on modules only have dependencies required for specific implementation.
- Testability Built by TDD enthusiasts, so supports super-easy mechanisms for testing.
- Modularity: Common behaviours are abstracted into the
http4k-coremodule, but there are several pluggable modules for different purposes.
Project website: https://www.http4k.org/
Github Project Organization: https://github.com/http4k
