Adding XML encoding/decoding support is a matter of providing a body serializer and/or a response body specification (similarly as it is done for JSON format). The process of adding integrations is fairly easy, and for now, one guide on how to use scalaxb tool is provided.


If you possess the XML Schema definition file (.xsd file) consider using the scalaxb tool, which would generate needed models and serialization/deserialization logic. To use the tool please follow the documentation on setting up and running scalaxb.

After code generation, create the SttpScalaxbApi trait (or trait with another name of your choosing) and add the following code snippet:

import generated.defaultScope // import may differ depending on location of generated code
import scalaxb.`package`.{fromXML, toXML} // import may differ depending on location of generated code
import scalaxb.{CanWriteXML, XMLFormat} // import may differ depending on location of generated code
import sttp.client4.{BodySerializer, ResponseAs, ResponseException, StringBody, asString}
import sttp.model.MediaType

import scala.xml.{NodeSeq, XML}

trait SttpScalaxbApi {
  case class XmlElementLabel(label: String)

  implicit def scalaxbBodySerializer[B](implicit format: CanWriteXML[B], label: XmlElementLabel): BodySerializer[B] = { (b: B) =>
    val nodeSeq: NodeSeq = toXML[B](obj = b, elementLabel = label.label, scope = defaultScope)
    StringBody(nodeSeq.toString(), "utf-8", MediaType.ApplicationXml)

  implicit def deserializeXml[B](implicit decoder: XMLFormat[B]): String => Either[Exception, B] = { (s: String) =>
    try {
    } catch {
      case e: Exception => Left(e)

  def asXml[B: XMLFormat]: ResponseAs[Either[ResponseException[String, Exception], B], Any] =
      .showAs("either(as string, as xml)")

This would add BodySerializer needed for serialization and asXml method needed for deserialization. Please notice, that fromXML, toXML, CanWriteXML, XMLFormat and defaultScope are members of code generated by scalaxb.

Next to this trait, you might want to introduce sttpScalaxb package object to simplify imports.

package object sttpScalaxb extends SttpScalaxbApi

From now on, XML serialization/deserialization would work for all classes generated from .xsd file as long as XMLFormat for the type in the question and XmlElementLabel for the top XML node would be implicitly provided in the scope.

Usage example:

val backend: SyncBackend = DefaultSyncBackend()
val requestPayload = Outer(Inner(42, b = true, "horses"), "cats") // `Outer` and `Inner` classes are generated by scalaxb from xsd file

import sttpScalaxb._ // imports sttp related serialization / deserialization logic
implicit val label = XmlElementLabel("outer") // gives needed XmlElementLabel for the top XML node
import generated.Generated_OuterFormat // imports member of code generated by scalaxb, that provides `XMLFormat` for `Outer` type; this import may differ depending on location of generated code

val response: Response[Either[ResponseException[String, Exception], Outer]] =