Simple Functional Domain Driven Example

A Scala implementation for creating RESTful apps with functional programming and DDD mindset. Its simplicity is ideal for anyone who self-learn scala and DDD.

Moveon

Application for making movie seat reservation. The domain is simple and completely described in one single algebra.

trait ReservationAlg[Allocation, Movie, Session] {
  def initSession(allocation: Allocation, movie: Movie, seats: Int): Future[Session]
  def reserve(session: Session, seats: Int = 1): Future[Session]
  def find(allocation: Allocation, movie: Movie): Future[(Session, Movie)]
}

Getting started

Go to the root directory of this project. Execute docker-compose up to start moveon server, mysql and external mock server. Fire up sbt and use these commands:

test     # starting unit test
it:test  # starting integration test, make sure to fire up 'docker-compose up' first
run      # starting moveon server, not necessary if you fired 'docker-compose up'

Please note that running integration test more than once will trigger an error, since the state is not restarted. You can manually call the endpoints using any http client, this example is using httpie.

http -v :8080/movies/register screenId=SCN2 imdbId=tt0059742 availableSeats=2

POST /movies/register HTTP/1.1
User-Agent: HTTPie/0.9.9
Accept-Encoding: gzip, deflate
Accept: application/json, */*
Connection: keep-alive
Content-Type: application/json
Content-Length: 66
Host: localhost:8080

{"screenId": "SCN2", "imdbId": "tt0059742", "availableSeats": "2"}

HTTP/1.1 200 OK
Server: akka-http/10.0.10
Date: Wed, 25 Oct 2017 01:06:43 GMT
Content-Type: application/json
Content-Length: 11

"tt0059742"

By adding -v to httpie, the request will be displayed in details.

After it is registered, we can reserve 1 seat on that session.

http -v :8080/movies/reserve screenId=SCN2 imdbId=tt0059742

Let’s look session’s status.

http :8080/movies screenId==SCN2 imdbId==tt0059742

HTTP/1.1 200 OK
Server: akka-http/10.0.10
Date: Wed, 25 Oct 2017 01:18:33 GMT
Content-Type: application/json
Content-Length: 111

{"imdbId":"tt0059742","screenId":"SCN2","movieTitle":"The Sound of Music","availableSeats":1,"reservedSeats":1}

As expected, available seats should be 1 as with reserved seats.

Now, what about making request more than the available seats? Fire up registration twice, the second attempt will give us a bad request.

HTTP/1.1 400 Bad Request
Server: akka-http/10.0.10
Date: Wed, 25 Oct 2017 01:22:17 GMT
Content-Type: text/plain; charset=UTF-8
Content-Length: 36

available seats must not be negative

Main technology stack

akka-http for both http client and server
circe for encoding and decoding Json
macwire for dependency injection
slick for accessing database
scala for language and standard libraries
docker for containerization and server dependencies
mysql for, well, mysql
wiremock for mock http server

Unfortunately, no scalaz or cats, all the monads is implemented using plain, simple and happy scala libraries :)

arinal/moveon

Simple Functional Domain Driven Example

Moveon

Getting started

Main technology stack