Thanks @dave! It’s as simple as this:

import org.http4k.contract.*
import org.http4k.core.*
import org.http4k.format.Jackson
import org.http4k.format.Jackson.auto
import org.http4k.routing.bind
import org.http4k.routing.routes
import org.http4k.server.Jetty
import org.http4k.server.asServer

data class MyDataClass(val something: String)
val requestBody = Body.auto<MyDataClass>().toLens()

fun main(args: Array<String>) {
    routes(
        "/api" bind contract(OpenApi(ApiInfo("My great API", "v1.0"), Jackson),"/route" meta {
            body = requestBody
        } bindContract Method.GET to ::handler)
    ).asServer(Jetty(5000)).start()
}

fun handler(request: Request): Response {
    return Response(Status.OK)
}

gives me

{
  “swagger” : “2.0",
  “info” : {
    “title” : “My great API”,
    “version” : “v1.0”,
    “description” : “”
  },
  “basePath” : “/”,
  “tags” : [ ],
  “paths” : {
    “/api/route” : {
      “get” : {
        “tags” : [ “/api” ],
        “summary” : “<unknown>“,
        “description” : null,
        “produces” : [ ],
        “consumes” : [ “application/json” ],
        “parameters” : [ {
          “in” : “body”,
          “name” : “body”,
          “description” : null,
          “required” : true,
          “type” : “object”
        } ],
        “responses” : { },
        “supportedContentTypes” : [ ],
        “security” : [ ]
      }
    }
  },
  “securityDefinitions” : { },
  “definitions” : { }
}

Yeah - you'll need to give http4k an example of your body to get this to work.

Ahh got it, so I need this for example:

receiving(requestBody to MyDataClass("example"))

I'll check the docs for an example. Thanks 😀