graphient: A Scala repository from erdeszt

GraphQL client for Sangria schemas

Library for generating and executing Graphql queries based on Sangria schemas.

Usage:

Add the packages to your build:

resolvers += Resolver.bintrayRepo("erdeszt", "io.github.erdeszt")
libraryDependencies += "io.github.erdeszt" %% "graphient" % "7.0.0"
libraryDependencies += "io.github.erdeszt" %% "graphient-circe" % "3.0.0" // For circe support
libraryDependencies += "io.github.erdeszt" %% "graphient-spray" % "3.0.0" // For spray support

Using the high level client

Import the graphient package and your favorite serializer:

// Graphient client
import graphient._
import graphient.model._
// Graphient serializer
import graphient.serializer.circe._  // for circe support
// or
import graphient.serializer.spray._  // for spray support

Import your favorite sttp backend(in this example we'll use `AsyncHttpClientCatsBackend` with `IO` from `cats-effect`)

Add the backend to your build:

libraryDependencies += "com.softwaremill.sttp.client" %% "async-http-client-backend-cats" % "1.6.7"

Graphient uses sttp 1.6.7 so your backend has to be compatible with it.

Create an implicit backend(the effect type has to support MonadError[?[_], Throwable] from cats-effect):

import cats.effect.IO
import sttp.client.asynchttpclient.cats._

implicit val sttpBackend = AsyncHttpClientCatsBackend[IO]()

Create a Graphient client with your schema (TestSchema definition):

import sttp.model._ // For the `uri` string interpolator

val client = new GraphientClient(TestSchema.schema, uri"http://yourapi.com/graphql")

Executing the queries with the client

execute via the GraphientClient

val query = Query(TestSchema.Queries.getUser)
val parameters = Map("userId", 1)
val responseData = client.call[TestSchema.Domain.User](query, parameters)

responseData is an IO[TestSchema.Domain.User], errors are propagated using MonadError from cats-effect

generate the sttp request and execute it manually

val query = Query(TestSchema.Queries.getUser)
val parameters = Map("userId", 1)
val request = client.createRequest(query, parameters)
val response = request.toOption.get.send() // Do not call .toOption.get in real code!

request is an Either[GraphqlCallError, Request[String, Nothing]], you have to unwrap the Either and execute the request manually

response is an IO[Response[String]]

Adding extra headers

Both call and createRequest supports adding extra headers to the request by passing in a varying number of (String, String) values starting from position 3

client.createRequest(query, parameters, ("Authorization", "Bearer mytoken"))
client.call(query, parameters, ("Authorization", "Bearer mytoken"))

Other modes

import graphient._
import graphient.model._

Create a query & a variable generator based on some Sangria schema

val queryGenerator = new QueryGenerator(TestSchema)
val variableGenerator = new VariableGenerator(TestSchema)

Generate a query or a mutation using either the schema directly or the name of the query:

val queryByDefinition = queryGenerator.generateQuery(Query(TestSchema.Queries.getUser))
val queryByName = queryGenerator.generateQuery(QueryByName("getUser"))
val mutationByDefinition = queryGenerator.generateQuery(Mutation(TestSchema.Mutations.get.createUser))
val mutationByName = queryGenerator.generateQuery(MutationByName("createUser"))

Generate variables for the query and the mutation

val variablesForGetUser = variableGenerator.generateVariables(
  QueryByName("getUser"),
  Map[String, Any]("userId" -> 1L)
)
val variablesForCreateUser = variableGenerator.generateVariables(
  MutationByName("createUser"),
  Map[String, Any](
    "name"    -> "user 1",
    "age"     -> 26,
    "hobbies" -> List("coding", "debugging")
  )
)

You can execute the queries in memory using a sangria.execution.Executor:

val result = Executor.execute(
  schema      = TestSchema,
  queryAst    = queryByName.right.toOption.get,
  userContext = context,
  variables   = variablesForGetUser.right.toOption.get
)

Or pretty print it with sangria.renderer.QueryRenderer along with the variables using the sangria.marshalling.QueryAstInputUnmarshaller

val renderedQuery = QueryRenderer.render(mutationByDefinition.right.toOption.get)
// =
// mutation ($name: String!, $age: Int!, $hobbies: [String!]!) {
//   createUser(name: $name, age: $age, hobbies: $hobbies) {
//     id
//     name
//     age
//     hobbies
//   }
// }

val unmarshaller = new QueryAstInputUnmarshaller()
val renderedVariables = unmarshaller.render(variablesForCreateUser.right.toOption.get)
// = {name:"user 1",age:26,hobbies:["coding","debugging"]}

For further examples check graphient/src/test/scala/graphient/Worksheet.sc and the specs in grahpeint/src/test and graphient/src/it.

erdeszt/graphient