How to use GraphQL with Retrofit on Android?

Question

I'm new to GraphQL but I have been using Retrofit for a while now and its easy to use and fast. GraphQL is much different than rest apis in terms of how you pass data. There really are not too many tutorials out there on using GraphQL with Android, I was only able to find this video (https://www.youtube.com/watch?v=P0uJHI7GjIc&t=1s) but there is no real code in there.

In my current code for retrofit calls I have an endpoint I set like so:

final RestAdapter restAdapter = new RestAdapter.Builder()
                .setEndpoint(endPoint)
                .build();
        T service = restAdapter.create(clazz);

Then I call a rest service like this:

@GET("/users/{login}")
    Observable<Github> getUser(@Path("login") String login);

Now with GraphQL you only have a base url and no service path. Also if you are querying like userId=1 then you have to send as Post with Body parameters:

operationName: arbitrary name ,
query: "{users(userid:$userId){username}}, 
variables: "{"userId":1}"

I'm just not sure how this translates to Retrofit

Answer 1

In your manifest to add

<uses-permission android:name="android.permission.INTERNET"/>

Your dependencies

// Kotlin Coroutines
implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.4'

//OkHttp
implementation ("com.squareup.okhttp3:okhttp:3.12.12"){
  force = true //API 19 support
}
implementation 'com.squareup.okhttp3:logging-interceptor:3.12.12'

//retrofit
implementation "com.squareup.retrofit2:retrofit:2.7.1"
implementation "com.squareup.retrofit2:converter-scalars:$2.7.1"

Also Java 8 compatibility

android {

    ...
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }

    kotlinOptions {
        jvmTarget = "1.8"
    }
}

With the service

import retrofit2.Response
import retrofit2.http.Body
import retrofit2.http.Headers
import retrofit2.http.POST

interface GraphQLService {

    @Headers("Content-Type: application/json")
    @POST("/")
    suspend fun postDynamicQuery(@Body body: String): Response<String>
}

you can create a object

import retrofit2.Retrofit
import retrofit2.converter.scalars.ScalarsConverterFactory

object GraphQLInstance {

    private const val BASE_URL: String = "http://192.155.1.55:2000/"

    val graphQLService: GraphQLService by lazy {
        Retrofit
            .Builder()
            .baseUrl(BASE_URL)
            .addConverterFactory(ScalarsConverterFactory.create())
            .build().create(GraphQLService::class.java)
    }
}

In the activity you can create this method

private fun post(userId: String){
    val retrofit = GraphQLInstance.graphQLService
    val paramObject = JSONObject()
    paramObject.put("query", "query {users(userid:$userId){username}}")
    GlobalScope.launch {
        try {
            val response = retrofit.postDynamicQuery(paramObject.toString())
            Log.e("response", response.body().toString())
        }catch (e: java.lang.Exception){
            e.printStackTrace()
        }
    }
}

You can check the example in GitHub and my post

Note: if you need a mutation should be to change this line

paramObject.put("query", "query {users(userid:$userId){username}}")

to

paramObject.put("query", "mutation {users(userid:$userId){username}}")

Answer 2

Building Queries & Parsing responses for GraphQL is not straightforward. If you are using this on pet-projects, i recommend to start exploring Apollo. This client is under serious development but you can already have a look and play with it.

https://github.com/apollographql/apollo-android

I enjoyed working with Apollo so far, and there are nice features on their roadmap: RxJava Integration, Retrofit, Subscriptions and support for AutoValue