Running as an http4s server¶
To expose an endpoint as an http4s server, first add the following dependency:
"com.softwaremill.tapir" %% "tapir-akka-http4s" % "0.2"
and import the package:
This adds an extension method to the
toRoutes. It requires the logic of the endpoint to be given as
a function of type:
[I as function arguments] => F[Either[E, O]]
F[_] is the chosen effect type. Note that the function doesn’t take the tuple
I directly as input, but instead
this is converted to a function of the appropriate arity. For example:
import tapir._ import tapir.server.http4s._ import cats.effect.IO import org.http4s.HttpRoutes import cats.effect.ContextShift // will probably come from somewhere else implicit val cs: ContextShift[IO] = IO.contextShift(scala.concurrent.ExecutionContext.global) def countCharacters(s: String): IO[Either[Unit, Int]] = IO.pure(Right[Unit, Int](s.length)) val countCharactersEndpoint: Endpoint[String, Unit, Int, Nothing] = endpoint.in(stringBody).out(plainBody[Int]) val countCharactersRoutes: HttpRoutes[IO] = countCharactersEndpoint.toRoutes(countCharacters _)
HttpRoutes are the usual http4s
Kleisli-based transformation of a
Request to a
Response, and can
be further composed using http4s middlewares or request-transforming functions. The tapir-generated
captures from the request only what is described by the endpoint.
It’s completely feasible that some part of the input is read using a http4s wrapper function, which is then composed with the tapir endpoint descriptions. Moreover, “edge-case endpoints”, which require some special logic not expressible using tapir, can be always implemented directly using http4s.
The http4s interpreter accepts streaming bodies of type
Stream[F, Byte], which can be used both for sending
response bodies and reading request bodies. Usage:
streamBody[Stream[F, Byte]](schema, mediaType).
The interpreter can be configured by providing an implicit
Http4sServerOptions value and status mappers, see
common server configuration for details.
The http4s options also includes configuration for the blocking execution context to use, and the io chunk size.