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Take Control Of Your APIs With GraphQL Adam McNeilly - @AdamMc331 @AdamMc331 #AndroidMakers 1

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What Is GraphQL? @AdamMc331 #AndroidMakers 2

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What Is Why Use GraphQL? @AdamMc331 #AndroidMakers 3

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Let's Examine An Existing API @AdamMc331 #AndroidMakers 4

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PokeAPI1 // https://pokeapi.co/api/v2/pokemon/ { "count": 964, "next": "https://pokeapi.co/api/v2/pokemon/?offset=20&limit=20", "previous": null, "results": [ { "name": "bulbasaur", "url": "https://pokeapi.co/api/v2/pokemon/1/" }, { "name": "ivysaur", "url": "https://pokeapi.co/api/v2/pokemon/2/" }, { "name": "venusaur", "url": "https://pokeapi.co/api/v2/pokemon/3/" } ] } 1 https://pokeapi.co/ @AdamMc331 #AndroidMakers 5

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PokeAPI1 // https://pokeapi.co/api/v2/pokemon/squirtle // Originally 11,000 lines { "abilities": [], "base_experience": 63, "forms": [], "game_indices": [], "height": 5, "held_items": [], "id": 7, "is_default": true, "location_area_encounters": "https://pokeapi.co/api/v2/pokemon/7/encounters", "moves": [], "name": "squirtle", "order": 10, "species": {}, "sprites": {}, "stats": [], "types": [], "weight": 90 } 1 https://pokeapi.co/ @AdamMc331 #AndroidMakers 6

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What Are The Drawbacks Of REST APIs? @AdamMc331 #AndroidMakers 7

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What Are The Drawbacks Of REST APIs? • Responses may not have enough data @AdamMc331 #AndroidMakers 7

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What Are The Drawbacks Of REST APIs? • Responses may not have enough data • Responses may have too much data @AdamMc331 #AndroidMakers 7

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What Are The Drawbacks Of REST APIs? • Responses may not have enough data • Responses may have too much data • Responses are not controlled by the client @AdamMc331 #AndroidMakers 7

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What Are The Drawbacks Of REST APIs? • Responses may not have enough data • Responses may have too much data • Responses are not controlled by the client • Any changes to responses have to go through another developer @AdamMc331 #AndroidMakers 7

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Let's Examine A GraphQL API 2 2 https://github.com/lucasbento/graphql-pokemon @AdamMc331 #AndroidMakers 8

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GraphQL Query Syntax { pokemon(name: "bulbasaur") { // Put All Fields Here } } @AdamMc331 #AndroidMakers 9

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Only Get What You Ask For // Query { pokemon(name: "bulbasaur") { name } } // Response { "data": { "pokemon": { "name": "Bulbasaur" } } } @AdamMc331 #AndroidMakers 10

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Another Example // Query { pokemon(name: "bulbasaur") { name number } } // Response { "data": { "pokemon": { "name": "Bulbasaur", "number": "001" } } } @AdamMc331 #AndroidMakers 11

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What Are The Benefits Of GraphQL APIs? @AdamMc331 #AndroidMakers 12

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What Are The Benefits Of GraphQL APIs? • Responses have just enough data @AdamMc331 #AndroidMakers 12

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What Are The Benefits Of GraphQL APIs? • Responses have just enough data • Responses are controlled by the client @AdamMc331 #AndroidMakers 12

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What Are The Benefits Of GraphQL APIs? • Responses have just enough data • Responses are controlled by the client • Any changes to responses can be done by the client @AdamMc331 #AndroidMakers 12

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Understanding GraphQL @AdamMc331 #AndroidMakers 13

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GraphiQL Interface @AdamMc331 #AndroidMakers 14

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Documentation Explorer @AdamMc331 #AndroidMakers 15

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Documentation Explorer • ! Indicates non-nullable @AdamMc331 #AndroidMakers 15

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Documentation Explorer • ! Indicates non-nullable • Brackets are array syntax @AdamMc331 #AndroidMakers 15

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Nested Objects @AdamMc331 #AndroidMakers 16

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GraphQL On Android @AdamMc331 #AndroidMakers 17

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Apollo GraphQL3 3 https://github.com/apollographql/apollo-android @AdamMc331 #AndroidMakers 18

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Adding Dependencies @AdamMc331 #AndroidMakers 19

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Create A GraphQL Directory @AdamMc331 #AndroidMakers 20

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Defining Your Schema @AdamMc331 #AndroidMakers 21

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Introspection Query 4 4 https://graphqlmastery.com/blog/graphql-introspection-and-introspection-queries @AdamMc331 #AndroidMakers 22

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Introspection Query 4 • A query that asks for meta data about a GraphQL Schema 4 https://graphqlmastery.com/blog/graphql-introspection-and-introspection-queries @AdamMc331 #AndroidMakers 22

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Introspection Query 4 • A query that asks for meta data about a GraphQL Schema • Will return all of the possible queries and mutations 4 https://graphqlmastery.com/blog/graphql-introspection-and-introspection-queries @AdamMc331 #AndroidMakers 22

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Introspection Query 4 • A query that asks for meta data about a GraphQL Schema • Will return all of the possible queries and mutations • Will return all of the models in a graph 4 https://graphqlmastery.com/blog/graphql-introspection-and-introspection-queries @AdamMc331 #AndroidMakers 22

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Introspection Query 4 • A query that asks for meta data about a GraphQL Schema • Will return all of the possible queries and mutations • Will return all of the models in a graph • Foot note has a deep dive into these queries 4 https://graphqlmastery.com/blog/graphql-introspection-and-introspection-queries @AdamMc331 #AndroidMakers 22

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Run Introspection Query @AdamMc331 #AndroidMakers 23

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Copy Result @AdamMc331 #AndroidMakers 24

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Paste Into schema.json @AdamMc331 #AndroidMakers 25

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Writing Your Queries @AdamMc331 #AndroidMakers 26

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Create A [something].graphql File // pokemonqueries.graphql // same directory as our schema.json file query PokemonQuery($first: Int!) { pokemonList: pokemons(first: $first) { name types image } } @AdamMc331 #AndroidMakers 27

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Build Our Project @AdamMc331 #AndroidMakers 28

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Generated Java Classes For Our Queries @AdamMc331 #AndroidMakers 29

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Write A Query From Our Code val query = PokemonQuery.builder() .first(DEFAULT_LIMIT) .build() val callback = object : ApolloCall.Callback() { override fun onFailure(e: ApolloException) { Log.e("ApolloService", e.message, e) } override fun onResponse(response: Response) { val pokemonList = response.data() ?.pokemonList() ?.map { apolloPokemon -> val name = apolloPokemon.name() val typeNames = apolloPokemon.types() val image = apolloPokemon.image() } } } apolloClient.query(query).enqueue(callback) @AdamMc331 #AndroidMakers 30

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Write A Query From Our Code val query = PokemonQuery.builder() .first(DEFAULT_LIMIT) .build() val callback = object : ApolloCall.Callback() { override fun onFailure(e: ApolloException) { Log.e("ApolloService", e.message, e) } override fun onResponse(response: Response) { val pokemonList = response.data() ?.pokemonList() ?.map { apolloPokemon -> val name = apolloPokemon.name() val typeNames = apolloPokemon.types() val image = apolloPokemon.image() } } } apolloClient.query(query).enqueue(callback) @AdamMc331 #AndroidMakers 30

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Write A Query From Our Code val query = PokemonQuery.builder() .first(DEFAULT_LIMIT) .build() val callback = object : ApolloCall.Callback() { override fun onFailure(e: ApolloException) { Log.e("ApolloService", e.message, e) } override fun onResponse(response: Response) { val pokemonList = response.data() ?.pokemonList() ?.map { apolloPokemon -> val name = apolloPokemon.name() val typeNames = apolloPokemon.types() val image = apolloPokemon.image() } } } apolloClient.query(query).enqueue(callback) @AdamMc331 #AndroidMakers 30

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Write A Query From Our Code val query = PokemonQuery.builder() .first(DEFAULT_LIMIT) .build() val callback = object : ApolloCall.Callback() { override fun onFailure(e: ApolloException) { Log.e("ApolloService", e.message, e) } override fun onResponse(response: Response) { val pokemonList = response.data() ?.pokemonList() ?.map { apolloPokemon -> val name = apolloPokemon.name() val typeNames = apolloPokemon.types() val image = apolloPokemon.image() } } } apolloClient.query(query).enqueue(callback) @AdamMc331 #AndroidMakers 30

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Write A Query From Our Code val query = PokemonQuery.builder() .first(DEFAULT_LIMIT) .build() val callback = object : ApolloCall.Callback() { override fun onFailure(e: ApolloException) { Log.e("ApolloService", e.message, e) } override fun onResponse(response: Response) { val pokemonList = response.data() ?.pokemonList() ?.map { apolloPokemon -> val name = apolloPokemon.name() val typeNames = apolloPokemon.types() val image = apolloPokemon.image() } } } apolloClient.query(query).enqueue(callback) @AdamMc331 #AndroidMakers 30

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Understanding The Generated Code @AdamMc331 #AndroidMakers 31

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Understanding The Generated Code @AdamMc331 #AndroidMakers 32

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Understanding The Generated Code @AdamMc331 #AndroidMakers 33

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Understanding The Generated Code @AdamMc331 #AndroidMakers 34

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Creating An Apollo Client val okHttpClient = OkHttpClient.Builder() .build() val apolloClient = ApolloClient.builder() .serverUrl("https://graphql-pokemon.now.sh/") .okHttpClient(okHttpClient) .build() @AdamMc331 #AndroidMakers 35

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You Wrote Your First GraphQL Query @AdamMc331 #AndroidMakers 36

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Going Further With Apollo @AdamMc331 #AndroidMakers 37

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Use Kotlin Models // build.gradle or build.gradle.kts apollo { generateKotlinModels.set(true) // or false for Java models } @AdamMc331 #AndroidMakers 38

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Query Code Is More Modern // repository.kt // No builder pattern val query = PokemonQuery(first = DEFAULT_LIMIT) // Use fields not methods val name = apolloPokemon.name val typeNames = apolloPokemon.types val image = apolloPokemon.image @AdamMc331 #AndroidMakers 39

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GraphQL Fragments @AdamMc331 #AndroidMakers 40

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Queries With Duplicated Code query PokemonQuery($first: Int!) { pokemonList: pokemons(first: $first) { name types image } } query PokemonDetailQuery($pokemonName: String) { pokemon: pokemon(name: $pokemonName) { name types image } } @AdamMc331 #AndroidMakers 41

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Share Information With A Fragment fragment ApolloPokemon on Pokemon { name types image } query PokemonQuery($first: Int!) { pokemonList: pokemons(first: $first) { ...ApolloPokemon } } query PokemonDetailQuery($pokemonName: String) { pokemon: pokemon(name: $pokemonName) { ...ApolloPokemon } } @AdamMc331 #AndroidMakers 42

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Migrating To GraphQL @AdamMc331 #AndroidMakers 43

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A Common Problem /** * This class has a direct dependency on a REST API. * It returns a data class we defined. * Not the data class generated by Apollo. * This makes swapping them difficult. */ class PokemonListViewModel( private val restApi: PokemonAPI ) : ViewModel() { @AdamMc331 #AndroidMakers 44

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Leverage Repository Interfaces interface PokemonRepository { fun getPokemonList(): PokemonListResponse? fun getPokemonDetail(pokemonName: String): Pokemon? } class PokemonListViewModel( private val repository: PokemonRepository ) : ViewModel() { @AdamMc331 #AndroidMakers 45

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Create Multiple Implementations class RetrofitService(): PokemonRepository { } class ApolloService(): PokemonRepository { } @AdamMc331 #AndroidMakers 46

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Allows You To A/B Test Your New API private fun getRepository(): PokemonRepository { if (isInGraphQLTestGroup) { return ApolloService() } else { return RetrofitService() } } @AdamMc331 #AndroidMakers 47

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Why A/B Test A New API? @AdamMc331 #AndroidMakers 48

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Why A/B Test A New API? • You can monitor performance of a page using different APIs @AdamMc331 #AndroidMakers 48

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Why A/B Test A New API? • You can monitor performance of a page using different APIs • This is a big change, you should ship with confidence @AdamMc331 #AndroidMakers 48

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Why A/B Test A New API? • You can monitor performance of a page using different APIs • This is a big change, you should ship with confidence • You won't need to do this for every page, but is helpful for your first page to use GraphQL @AdamMc331 #AndroidMakers 48

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Dealing With Generated Code @AdamMc331 #AndroidMakers 49

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Our Repository Doesn't Return Generated Code interface PokemonRepository { fun getPokemonList(): PokemonListResponse? fun getPokemonDetail(pokemonName: String): Pokemon? } @AdamMc331 #AndroidMakers 50

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Leverage Kotlin Extension Functions // pokemonqueries.graphql fragment ApolloPokemon on Pokemon { name types image } // ApolloService.kt private fun ApolloPokemon.toPokemon(): Pokemon { return Pokemon( name = this.name.orEmpty(), firstType = this.types?.getOrNull(0), secondType = this.types?.getOrNull(1), frontSpriteUrl = this.image ) } @AdamMc331 #AndroidMakers 51

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Makes The Parsing Of Requests Cleaner val callback = object : ApolloCall.Callback() { override fun onFailure(e: ApolloException) { Log.e("ApolloService", e.message, e) } override fun onResponse(response: Response) { val pokemonList = response.data() ?.pokemonList ?.filterNotNull() ?.map { apolloPokemon -> val pokemon = apolloPokemon.fragments.apolloPokemon.toPokemon() } } } @AdamMc331 #AndroidMakers 52

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Consuming Apollo API Requests @AdamMc331 #AndroidMakers 53

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Callbacks val callback = object : ApolloCall.Callback() { override fun onFailure(e: ApolloException) { // ... } override fun onResponse(response: Response) { // ... } } @AdamMc331 #AndroidMakers 54

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RxJava25 val query = PokemonQuery(first = DEFAULT_LIMIT) apolloClient.rxQuery(query) .subscribeOn(Schedulers.io()) .observeOn(AndroidSchedulers.mainThread()) .subscribe { // ... } 5 https://www.apollographql.com/docs/android/advanced/rxjava2/ @AdamMc331 #AndroidMakers 55

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Coroutines6 override suspend fun getPokemon(): PokemonResponse { val query = PokemonQuery(first = DEFAULT_LIMIT) val response = apolloClient.query(query).toDeferred().await() } 6 https://www.apollographql.com/docs/android/advanced/coroutines/ @AdamMc331 #AndroidMakers 56

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One Last Suggestion @AdamMc331 #AndroidMakers 57

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JS GraphQL Plugin7 7 https://jimkyndemeyer.github.io/js-graphql-intellij-plugin/ @AdamMc331 #AndroidMakers 58

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Thank You! @AdamMc331 #AndroidMakers 59