From Restful to GraphQL

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From RESTful to GraphQL José María Rodríguez Hurtado @durbon chema@durbon.com 1 #CodemotionMadrid

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2 I’m Chema Android Team Lead at @JobandtalentEng Editor Genbeta @durbon

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3 “Instead of working with rigid server-defined endpoints, you can send queries to get exactly the data you’re looking for in one request”

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Agenda Reviewing RESTful Working on product teams with APIs GraphQL 4

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¿Using REST correctly? Nick Schrock. React London Meetup. 2015 6

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Reviewing RESTful - Define separate resources. Fetch via URI - These resources are manipulated using HTTP requests where the method (GET, POST, PUT, PATCH, DELETE) has specific meaning. - Discover resources, thanks to HATEOAS (Hypertext As The Engine Of Application State). 7

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8 https://medium.com/@leeshapton/mental-maps-for-teaching-graphql-to-beginners-9db9b85ac957

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Collections of API RESTFul Endpoint resources GET /posts - Retrieves a list of posts GET /posts/12 - Retrieves a specific post GET /posts/12/comments - Retrieves comments GET /posts/12/comments/42/ - Retrieve specific comment POST /posts - Creates a new post PUT /posts/12 - Updates post #12 with payload provided PATCH /posts/12 - Partially updates post #12 DELETE /posts/12 - Deletes post #12 9

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Example Payload JSON { "name": "Luke Skywalker", "height": "172", "mass": "77", "hair_color": "blond", "skin_color": "fair", "eye_color": "blue", "birth_year": "19BBY", "gender": "male", "homeworld": "http://swapi.co/api/planets/1/", "films": [ "http://swapi.co/api/films/6/", "http://swapi.co/api/films/3/", "http://swapi.co/api/films/2/", "http://swapi.co/api/films/1/", "http://swapi.co/api/films/7/" ], "species": [ "http://swapi.co/api/species/1/" ], "vehicles": [ "http://swapi.co/api/vehicles/14/", "http://swapi.co/api/vehicles/30/" ], "starships": [ "http://swapi.co/api/starships/12/", "http://swapi.co/api/starships/22/" 10

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Problems Working with APIs 11

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13 Where is my API? Where are my endpoints? Why does it not work? How many endpoint will be needed? How many changes should we do?

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Excessive Round Trips Client - R 14

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Payload and bandwidth 15

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/filmsWithDirectorAndTag /filmsWithPrincipalsCharacter /filmSummaries/1 /filmsDetails/1 /filmSummaryWithActors/1 Custom Endpoints or BFF (aka “spaghettification”) 16

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Versioning APIs: breaking changes 17 What is the correct way to version my API? - The URL way? /api/v1/post/12232 V2, v3, v4….?? - The Header way? GET /api/article/1234 HTTP/1.1 Accept: application/vnd.api.article+xml; version=1.0

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Why not like REST? - Most REST API are really Ad-hoc RPC with custom endpoint definitions. Time spent maintaining many versioned endpoint - REST requires many requests (many Roundtrips) - With REST, you request too much or too little data REST often turns into a maze of poorly-documented endpoints - Weak Typing and Poor Metadata 18

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GraphQL isn't a new technology. Facebook: It has been delivering data to mobile News Feed since 2012 20

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GraphQL is a query language, like SQL? You don’t connect GraphQL directly to your backend or database. It’s an API layer, just like REST. GraphQL can be layered over multiple backends and databases, without the client being aware of where the data is coming from, just like REST. 23

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“GraphQL is a query language designed to build client applications by providing an intuitive and flexible syntax and system for describing their data requirements and interactions.” - GraphQL Specification https://facebook.github.io/graphql/ 24

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Single Endpoint /graphql 25

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26 https://medium.com/@leeshapton/mental-maps-for-teaching-graphql-to-beginners-9db9b85ac957

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Query Language “hello world” Query { me { name } } { "me": { "name": "@durbon" } } 27

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{ speaker(id: 27) { name profilePics { width height url } } } { "speaker": { "name": "@durbon" "profilePics" : { "width": 250, "height": 250, "url": "http://avatarurl.com/250.jpg" } } } Ask for you want 28

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{ speaker(id: 27) { name twitter profilePics(size: 640) { width height url } } } { "speaker": { "name": "Txema Rodríguez" "twitter": "@durbon" "profilePics" : { "width": 640, "height": 640, "url": "http://avatar.com/640.jpg" } } } Ask for you want 29

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{ speaker(id: 27) { name, licPic: profilePics (size: 90){ width, height, url }, bigPic: profilePics (size: 800){ width, height, url } } } "speaker": { "name": "Txema Rodríguez" "licPic" : { "width": 90, "height": 90, "url": "http://avatar.com/90.jpg" }, "bigPic" : { "width": 800, "height": 800, "url": "http://avatar.com/800.jpg" } } } Ask for you want 30

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Nested connection resources { me { name talks { title } } } { "me": { "name": "@durbon" "talks" : [ { title: "GraphQL is cool" }, { title: "API REST is dead" }, { title: "Kotlin in Android" },.. 31

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{ latestTalk { title, speaker { name, twitter } }, allSpeakers { name } } { "data": { "latestTalk": { "title": "¿Por qué deberíamos abandonar REST?", "speaker": { "name": "Txema Rodríguez", "twitter": "@durbon", } }, "allSpeakers": [ { "name": "Txema Rodriguez" }, { "name": "David Bonilla" } ] } } 32 Combining Queries

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Mutation: also you can write using GraphQL: mutation { writePost (input : { author: “durbon”, title: “graphql for beginners” content: "it's awesome." }) { id, title } } 34

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GraphQL Core principles 35

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Type System GraphQL schema language it's similar to the query language, and allows us to talk about GraphQL schemas in a language-agnostic way. 36

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Schemas and types - Object types with fields: speakers, talks,... - Scalar types: Int, Float, String, Boolean, ID - Lists and Non-Null - Arguments: every field on a GraphQL object type can have zero or more arguments - Enumeration types: a special kind of scalar that is restricted to a particular set of allowed values 37

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The GraphQL schema provides a clear contract for client-server communication Client Backend Possibilities GraphQL Type System GraphQL Schema Requirements GraphQL Languages Queries Mutation App Server View 38

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Schema type Query { me: Speaker speaker (id: Int): Speaker! } type ProfilePicture { width: Int! height: Int! url: String! } type Speaker { name: String! profilePicture(size: Int = 50): ProfilePicture talks: [Talks!] } 39 input TalkInput{ content: String! author: Speaker! } type Mutation { createTalk: (input: TalkInput): Talk } type Talk { author: Speaker! content: String! }

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Introspection Creating documentation, or rich IDE experiences 40

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IntrospectionQuery { __type(name: "Speaker") { name description } } { "data": { "__type": { "name": "Speaker", "description": "The speaker of a talk.", } } } 41

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IntrospectionQuery query IntrospectionQueryTypeQuery { __schema { queryType { name fields { name description type { name kind } } } } } { "data": { "__type": { "name": "Developer", “Description”: “Name developer” "fields": [ { "name": "id", "type": { "name": null, "kind": "NON_NULL" } }, { "name": "name", "type": { "name": null, "kind": "NON_NULL" } 42

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Documentation by default Generates API documentation for our consumers, and prevents us from spending precious coding time on documentation. 43

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Static validation & IDE Integration 45

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Code Generation: write queries, not code 46

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Execution After being validated, a GraphQL query is executed by a GraphQL server which returns a result that mirrors the shape of the requested query 47

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Database “Microservices” Remote Services whatever your tech stack Your existing code GraphQL Execution 49

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Object, consisting of two major components: ● the schema definition ● the actual implementation in the form of resolver functions 50 Structure vs Behaviour

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Think in Graph, not endpoint Fields independently of each other. Apply different context in order to retrieve such data 51

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Each field on each type is backed by a function called the resolver which is provided by the GraphQL server When a field is executed, the corresponding resolver is called to produce the next value. 52

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53 https://blog.graph.cool/graphql-server-basics-the-schema-ac5e2950214e

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54 Every feature you build first manifests itself in the GraphQL schema — then gets implemented through corresponding resolvers it allows frontend developers to start working against a mocked API, before it is actually implemented by backend developers Schema First development

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55 Catching

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58 Stitching in a gateway

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59 Stitching in a gateway

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61 GraphQL.org

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Draft RFC Specification for GraphQL https://facebook.github.io/graphql/ 62

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Reference implementation of GraphQL https://github.com/graphql/graphql-js 63

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Javascript Python (graphene) Scala (sangria) Ruby Java Clojure Go PHP C# .NET Elixir Swift …. graphql.org/code/ 65

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Client library 66 Relay React iOS Android

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Public GraphQL APIs 68 Early Github GraphQL API https://developer.github.com/early-access/graphql/explorer/ Yelp https://www.yelp.es/developers/graphql/guides/intro SWAPI http://graphql.org/swapi-graphql/ More APIs https://github.com/APIs-guru/graphql-apis

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Benefits of Exposing Data Through GraphQL - Boost your client development: combining and Querying Data and Picking Your Payload - Specification: the spec determines the validity, Strongly Typed, hierarchical with nested fields - Structure vs Behaviour. This allows you to focus on separation of concerns, not technologies. 69

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@durbon 70 Thanks, #codemotionMadrid! We’re hiring candidates.jobandtalent.com/es/careers