http4s - get request body as String or InputStream

Peter's solution both corrects the question and answers it, but I stumbled here looking for the solution to OP's stated, but not intended, question: "how to get request body as [...] InputStream" in http4s. Thanks to the discussion in Issue 634 on GitHub, here's what I came up with:

import java.io.InputStream
import org.http4s._
implicit val inputStreamDecoder: EntityDecoder[InputStream] = 
    EntityDecoder.decodeBy(MediaRange.`*/*`) { msg =>
  DecodeResult.success(scalaz.stream.io.toInputStream(msg.body))
}

And then in your HttpService, use that decoder like so:

request.as[InputStream].flatMap { inputStream => ...inputStream is an InputStream... }

Or skip the whole Decoder dance, if you want:

val inputStream = scalaz.stream.io.toInputStream(request.body)

You can use the http4s-json4s-jackson (or http4s-json4s-native) packages and use an org.http4s.EntityDecoder to easily get a Foo (I renamed your Request case class to Foo below) from a request.

EntityDecoder is a type class which can decode an entity from the request body. We want to get the Foo posted in JSON, so we need to create an EntityDecoder[Foo] which can decode JSON. If we want to create this decoder using json4s we need a Reader (or a JsonFormat).

If you have an EntityDecoder[Foo] instance, we can get the Foo from the request with req.as[Foo].

import org.json4s._
import org.json4s.jackson.JsonMethods._

import org.http4s._
import org.http4s.dsl._
import org.http4s.json4s.jackson._

case class Foo(firstName: String, secondName: String)

// create a json4s Reader[Foo]
implicit val formats = DefaultFormats
implicit val fooReader = new Reader[Foo] { 
  def read(value: JValue): Foo = value.extract[Foo] 
}
// create a http4s EntityDecoder[Foo] (which uses the Reader)
implicit val fooDec = jsonOf[Foo]

val service = HttpService {
  case req @ POST -> Root => 
    // req.as[Foo] gives us a Task[Foo]
    // and since Ok(...) gives a Task[Response] we need to use flatMap
    req.as[Foo] flatMap ( foo => Ok(foo.firstName + " " + foo.secondName) )
}

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Note: The json libraries libraries used most often with http4s are probably argonaut and circe. So you might find more http4s examples using one of those libraries.