tapir, or Typed API descRiptions

With tapir, you can describe HTTP API endpoints as immutable Scala values. Each endpoint can contain a number of input and output parameters. An endpoint specification can be interpreted as:

  • a server, given the “business logic”: a function, which computes output parameters based on input parameters. Currently supported:

  • a client, which is a function from input parameters to output parameters. Currently supported:

  • documentation. Currently supported:

Tapir is licensed under Apache2, the source code is available on GitHub.

Depending on how you prefer to explore the library, take a look at one of the examples or read on for a more detailed description of how tapir works!

Tapir is available:

  • all modules - Scala 2.12 and 2.13 on the JVM

  • selected modules (core; http4s, vertx, netty, aws servers; sttp and http4s clients; openapi; some js and datatype integrations) - Scala 3 on the JVM

  • selected modules (aws server; sttp client; some js and datatype integrations) - Scala 2.12, 2.13 and 3 using Scala.JS.

Code teaser

import sttp.tapir._
import sttp.tapir.generic.auto._
import sttp.tapir.json.circe._
import io.circe.generic.auto._

type Limit = Int
type AuthToken = String
case class BooksFromYear(genre: String, year: Int)
case class Book(title: String)


// Define an endpoint

val booksListing: PublicEndpoint[(BooksFromYear, Limit, AuthToken), String, List[Book], Any] = 
  endpoint
    .get
    .in(("books" / path[String]("genre") / path[Int]("year")).mapTo[BooksFromYear])
    .in(query[Limit]("limit").description("Maximum number of books to retrieve"))
    .in(header[AuthToken]("X-Auth-Token"))
    .errorOut(stringBody)
    .out(jsonBody[List[Book]])


// Generate OpenAPI documentation

import sttp.tapir.docs.openapi.OpenAPIDocsInterpreter
import sttp.tapir.openapi.circe.yaml._

val docs = OpenAPIDocsInterpreter().toOpenAPI(booksListing, "My Bookshop", "1.0")
println(docs.toYaml)


// Convert to akka-http Route

import sttp.tapir.server.akkahttp.AkkaHttpServerInterpreter
import akka.http.scaladsl.server.Route
import scala.concurrent.Future

def bookListingLogic(bfy: BooksFromYear,
                     limit: Limit,
                     at: AuthToken): Future[Either[String, List[Book]]] =
  Future.successful(Right(List(Book("The Sorrows of Young Werther"))))
val booksListingRoute: Route = AkkaHttpServerInterpreter()
  .toRoute(booksListing.serverLogic((bookListingLogic _).tupled))


// Convert to sttp Request

import sttp.tapir.client.sttp.SttpClientInterpreter
import sttp.client3._

val booksListingRequest: Request[DecodeResult[Either[String, List[Book]]], Any] = 
  SttpClientInterpreter()
    .toRequest(booksListing, Some(uri"http://localhost:8080"))
    .apply((BooksFromYear("SF", 2016), 20, "xyz-abc-123"))

Other sttp projects

sttp is a family of Scala HTTP-related projects, and currently includes:

  • sttp client: the Scala HTTP client you always wanted!

  • sttp tapir: this project

  • sttp model: simple HTTP model classes (used by client & tapir)

Sponsors

Development and maintenance of sttp tapir is sponsored by SoftwareMill, a software development and consulting company. We help clients scale their business through software. Our areas of expertise include backends, distributed systems, blockchain, machine learning and data analytics.

Table of contents

Getting started

Endpoints

Server interpreters

Client interpreters

Documentation interpreters

Testing

Generators

Other subjects