Generating OpenAPI documentation

To use, add the following dependencies:

"com.softwaremill.sttp.tapir" %% "tapir-openapi-docs" % "0.12.11"
"com.softwaremill.sttp.tapir" %% "tapir-openapi-circe-yaml" % "0.12.11"

Tapir contains a case class-based model of the openapi data structures in the openapi/openapi-model subproject (the model is independent from all other tapir modules and can be used stand-alone).

An endpoint can be converted to an instance of the model by importing the package and calling the provided extension method:

import sttp.tapir.openapi.OpenAPI

val docs: OpenAPI = booksListing.toOpenAPI("My Bookshop", "1.0")

Such a model can then be refined, by adding details which are not auto-generated. Working with a deeply nested case class structure such as the OpenAPI one can be made easier by using a lens library, e.g. Quicklens.

Multiple endpoints can be converted to an OpenAPI instance by calling the extension method on a list of endpoints:

List(addBook, booksListing, booksListingByGenre).toOpenAPI("My Bookshop", "1.0")

The openapi case classes can then be serialised, either to JSON or YAML using Circe:

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



Options can be customised by providing an implicit instance of OpenAPIDocsOptions, when calling .toOpenAPI.

  • operationIdGenerator: each endpoint corresponds to an operation in the OpenAPI format and should have a unique operation id. By default, the name of endpoint is used as the operation id, and if this is not available, the operation id is auto-generated by concatenating (using camel-case) the request method and path.
  • linkFromChildToParent: should child schemas contain a backlink to the parent schema using allOf, in addition to the parent enumerating all children using oneOf. The default is true, but e.g. the Redoc visualisation might require this to be false.

Exposing OpenAPI documentation

Exposing the OpenAPI documentation can be very application-specific. However, tapir contains modules which contain akka-http/http4s routes for exposing documentation using Swagger UI or Redoc:

"com.softwaremill.sttp.tapir" %% "tapir-swagger-ui-akka-http" % "0.12.11"
"com.softwaremill.sttp.tapir" %% "tapir-swagger-ui-http4s" % "0.12.11"
"com.softwaremill.sttp.tapir" %% "tapir-redoc-http4s" % "0.12.11"

Note: tapir-swagger-ui-akka-http transitively pulls some Akka modules in version 2.6. If you want to force your own Akka version (for example 2.5), use sbt exclusion. Mind the Scala version in artifact name:

"com.softwaremill.sttp.tapir" %% "tapir-swagger-ui-akka-http" % "0.12.11" exclude("com.typesafe.akka", "akka-stream_2.12")

Usage example for akka-http:

import sttp.tapir.openapi.circe.yaml._
import sttp.tapir.swagger.akkahttp.SwaggerAkka

val docsAsYaml: String = myEndpoints.toOpenAPI("My App", "1.0").toYaml
// add to your akka routes
new SwaggerAkka(docsAsYaml).routes

For http4s, use the SwaggerHttp4s or RedocHttp4s classes.