How to mount a servlet filter in blaze server (http4s)

Question

I am a newbie in scala world and using http4s for developing the REST layer of my application. I am using blaze server for deploying/publishing the services. I need to mount a servlet filter or interceptor in the flow before it reaches my HttpService methods. How can I do that?

Answer 1

http4s library has so called middleware functionality. Middleware functionality is a wrapper around your service. For example, you have simple endpoint:

 val helloWorldService = HttpService {
  case GET -> Root / "hello" / name =>
    Ok(s"Hello, $name.")
}

To apply middleware you may do the following:

     val service: HttpService = middleware(authedService)

      val authedService: AuthedService[User] =
        AuthedService {
          case GET -> Root / "welcome" as user => Ok(s"Welcome, ${user.name}")
        }
      val middleware = AuthMiddleware(authUser)

and your just need to implement your authUser :

val authUser: Service[Request, User] = ???

You may want to check out the org.http4s.server.middleware package for already existent middleware.