Explore creating robust HTTP services in Scala's functional programming paradigm. Gain insights into pure vs. impure implementations, their pros and cons, and effective tool usage.

scala-platform.tar.gz

Scala-Pure

Scala-Impure

Scala-Tapir

Scala-Impure-Test

Scala-Pure-Test

Scala-Tapir-Test

Test

Scala - Run Code Widget 

Scala-Pure-copy

Scala is one of the most popular general-purpose languages that supports both object-oriented and functional programming. In this course, you will learn how to create back-end HTTP services using Scala's functional programming paradigm.

You will also learn how to develop, test, and document the service using both pure and impure ways. You will be exposed to the differences between pure and impure implementation, their respective pros and cons, and how pure implementation can be more robust in terms of performance, understandability, testability, and type safeness. 

By the end of the course, you will have a clear idea of how functional programming works in Scala and how you can use the available tools more effectively.

Pure Functional HTTP APIs in Scala

# Create a product
Before we work on our Products Routes tests, we need to adapt the code to create a product using the knowledge we gained from our Product Route update test.


casereq @POST -> Root/ "products" => 
    req
        .as[Product]
        .flatMap { p =>
            for {
                cnt <- repo.saveProduct(p)
                res <- cnt match {
                    case 0 => NotFound()
                    case _ => InternalServerError()
                }
            } yield res
        }
        .handleErrorWith {
            case InvalidMessageBodyFailure(_, _) => BadRequest()
        }

# Garbage values

Moving on to our tests: We will start with sending garbage JSON via the POST request.

val expected StatusCode = Status.BadRequest

s"return$expectedStatusCode"in{
    def service: HttpRoutes[IO] =
        Router("/" -> new ProductsRoutes(emptyRepository).routes)
    val payload = scala.util.Random.alphanumeric.take(256).mkString
    val response: IO[Response[IO]] = service.orNotFound.run(
        Request(method = Method.POST, uri = Uri.uri("/products"))
            .withEntity(payload.asJson.noSpaces)
    )
    val result = response.unsafeRunSync
    result.status must be(expectedStatusCode)
    result.body.compile.toVector.unsafeRunSync must be(empty)
}

There is nothing special here. The test is the same as for the Product Routes except for the changed URI and HTTP method. The code is also a bit simpler because we do not need to generate a dynamic request URI like before.

# Saving with valid JSON

Learn how to test the routes for loading and creating products.

Introduction

Impure Implementation

Pure Implementation

Testing Impure Services

Testing Pure Services

Benchmarks

Documentation

Epilogue

Unit Tests for Products Routes Part 3

Create a product

Garbage values