A sample project using http4s, doobie, and circe.
The rest resources that this api provides are:
| Method | Url | Description |
|---|---|---|
| GET | /istypecasted?name=actorname | Returns "yes" or "no" indicating if an actor is typecasted. |
| GET | /matchingtitles?firstname=first&secondname=second | Returns list of matching titles for first and second actor, 404 when no matching titles are found. |
| POST | /associationWithKB?name=actorname | Determines the degree of an actor/actress from Kavin Bacon. 404 if no such actor/actress is present |
Here are some examples on how to use the microservice with curl, assuming it runs on the default port 8080:
Check if Al Pacino is typecasted:
curl http://localhost:8080/istypecasted?name=Al%20Pacino
Get matching list of titles for Al Pacino and Marlon Brando:
curl http://localhost:8080/matchingtitles?firstname=Al%20Pacino&secondname=Marlon%20Brando
Get Degree of association for Al Pacino with Kavin Bacon:
curl http://localhost:8080/associationWithKB?name=Al%20Pacino
The source of the data that the api uses is IMDb Datasets
The data contains information about titles of movies, tv-serials , actors/actress etc. The data is relational in nature with references between various datasets.
The api uses in memory H2 database to store the data.
Data loading starts as the server boots up and continous in the background while the server is ready to serve request.
case class Title(tconst: String, titleType: String, primaryTitle: String,
originalTitle: String, isAdult: String, startYear: Int,
endYear: Option[Int], runTimeInMinutes: Int, genres: String)case class Name(nconst: String, primaryName: String, birthYear: Int, deathYear: Option[Int], primaryProfession: String, knownForTitles: String)The api captures errors at various level : service, repository. All known business errors are represented
by a type BusinessError.
All service layer methods return an Either[BusinessError,A] type. To be more precise , since
we use the IO monad to represent side effects , the type returned by most methods is
EitherT[IO, BusinessError, A] which is aliased as ResultT[A] in the entire api
http4s is used as the HTTP layer. http4s provides streaming and functional HTTP for Scala. This example project uses cats-effect, but is possible to use http4s with another effect monad.
By using an effect monad, side effects are postponed until the last moment.
http4s uses fs2 for streaming. This allows to return streams in the HTTP layer so the response doesn't need to be generated in memory before sending it to the client.
In the example project this is done for the GET /todos endpoint.
doobie is used to connect to the database. This is a pure functional JDBC layer for Scala. This example project uses cats-effect in combination with doobie, but doobie can use another effect monad.
Because both http4s and doobie use an effect monad, the combination is still pure and functional.
circe is the recommended JSON library to use with http4s. It provides automatic derivation of JSON Encoders and Decoders.
pureconfig is used to read the configuration file application.conf.
This library allows reading a configuration into well typed objects.
h2 is used as a database. This is an in memory database, so when stopping the application, the state of the microservice is lost.
Using Flyway the database migrations are performed when starting the server.
This example project contains both unit tests, which mock the infrastructure.repository that accesses the database, and integration tests that use the http4s HTTP client to perform actual requests.
You can run the microservice with sbt run. By default it listens to port number 8080, you can change
this in the application.conf.
Please copy the title.basics.tsv and name.basics.tsv in src\main\resources to load the required data