JSON

Adding support for JSON (or other format) bodies in requests/responses is a matter of providing a body serializer and/or a response body specification. Both are quite straightforward to implement, so integrating with your favorite JSON library shouldn’t be a problem. However, there are some integrations available out-of-the-box.

Each integration is available as an import, which brings the implicit BodySerializers and asJson methods into scope. Alternatively, these values are grouped intro traits (e.g. sttp.client.circe.SttpCirceApi), which can be extended to group multiple integrations in one object, and thus reduce the number of necessary imports.

Following data class will be used through the next few examples:

case class RequestPayload(data: String)
case class ResponsePayload(data: String)

Circe

JSON encoding of bodies and decoding of responses can be handled using Circe by the circe module. To use add the following dependency to your project:

"com.softwaremill.sttp.client" %% "circe" % "2.2.1"

This module adds a body serialized, so that json payloads can be sent as request bodies. To send a payload of type T as json, a io.circe.Encoder[T] implicit value must be available in scope. Automatic and semi-automatic derivation of encoders is possible by using the circe-generic module.

Response can be parsed into json using asJson[T], provided there’s an implicit io.circe.Decoder[T] in scope. The decoding result will be represented as either a http/deserialization error, or the parsed value. For example:

import sttp.client._
import sttp.client.circe._

implicit val backend: SttpBackend[Identity, Nothing, NothingT] = HttpURLConnectionBackend()

import io.circe.generic.auto._
val requestPayload = RequestPayload("some data")

val response: Identity[Response[Either[ResponseError[io.circe.Error], ResponsePayload]]] =
  basicRequest
    .post(uri"...")
    .body(requestPayload)
    .response(asJson[ResponsePayload])
    .send()

Arbitrary JSON structures can be traversed by parsing the result as io.circe.Json, and using the circe-optics module.

Json4s

To encode and decode json using json4s, add the following dependency to your project:

"com.softwaremill.sttp.client" %% "json4s" % "2.2.1"
"org.json4s" %% "json4s-native" % "3.6.0"

Note that in this example we are using the json4s-native backend, but you can use any other json4s backend.

Using this module it is possible to set request bodies and read response bodies as case classes, using the implicitly available org.json4s.Formats (which defaults to org.json4s.DefaultFormats), and by bringing an implicit org.json4s.Serialization into scope.

Usage example:

import sttp.client._
import sttp.client.json4s._

implicit val backend: SttpBackend[Identity, Nothing, NothingT] = HttpURLConnectionBackend()

val requestPayload = RequestPayload("some data")

implicit val serialization = org.json4s.native.Serialization
implicit val formats = org.json4s.DefaultFormats

val response: Identity[Response[Either[ResponseError[Exception], ResponsePayload]]] =
  basicRequest
    .post(uri"...")
    .body(requestPayload)
    .response(asJson[ResponsePayload])
    .send()

spray-json

To encode and decode JSON using spray-json, add the following dependency to your project:

"com.softwaremill.sttp.client" %% "spray-json" % "2.2.1"

Using this module it is possible to set request bodies and read response bodies as your custom types, using the implicitly available instances of spray.json.JsonWriter / spray.json.JsonReader or spray.json.JsonFormat.

Usage example:

import sttp.client._
import sttp.client.sprayJson._
import spray.json._

implicit val backend: SttpBackend[Identity, Nothing, NothingT] = HttpURLConnectionBackend()

implicit val payloadJsonFormat: RootJsonFormat[RequestPayload] = ???
implicit val myResponseJsonFormat: RootJsonFormat[ResponsePayload] = ???

val requestPayload = RequestPayload("some data")

val response: Identity[Response[Either[ResponseError[Exception], ResponsePayload]]] =
  basicRequest
    .post(uri"...")
    .body(requestPayload)
    .response(asJson[ResponsePayload])
    .send()

play-json

To encode and decode JSON using play-json, add the following dependency to your project:

"com.softwaremill.sttp.client" %% "play-json" % "2.2.1"

To use, add an import: import sttp.client.playJson._.