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Dev sum - Beyond REST with GraphQL in .Net
- 1. #DevSum19 Beyond REST with GraphQL Irina Scurtu @irina_scurtu #DevSum19
- 2. #DevSum19 Irina Scurtu Romania Based Software Architect @Endava @irina_scurtu
- 3. #DevSum19 Agenda ▪ REST ▪ GraphQL ▪ GraphQL in .Net ▪ REST or GraphQL
- 4. #DevSum19 1. Client-server 2. Stateless 3. Cacheable 4. Uniform interface 1. Identification of resources 2. Resource representations 3. Self-descriptive messages 4. HATEOAS REST Constraints
- 5. #DevSum19 ▪ Scalable ▪ Server drives the application state ▪ Server & client can evolve independently ▪ Leverages : Verbs, Media Types, HTTP! ▪ Content negotiations ▪ Multiple representation of the same resource ▪ Discoverable ▪ Evolvable REST Apis benefits
- 6. #DevSum19 ▪ Intuitive ▪ Responds to different needs
- 7. #DevSum19 Rare REST Apis…. Hard to implement You need discipline Constant design Rely on HTTP Proven results
- 8. #DevSum19 1. Client-server 2. Stateless 3. Cacheable 4. Uniform interface 1. Identification of resources 2. Resource representations 3. Self-descriptive messages 4. HATEOAS REST-ish Constraints
- 9. #DevSum19 Everyone does them REST-ish Apis Almost, fully use HTTP Chatty performant
- 10. #DevSum19 Chatty
- 12. #DevSum19 ▪ Get more data than you use for your client ▪ Can be solved by continuously designing and trimming your API ▪IF YOU’re LUCKY Overfetching
- 13. #DevSum19 ▪ Forces you to make another call to get some data ▪ “get that, and that, and also that” Underfetching
- 15. #DevSum19 “a query language that solves the issue with overfetching & underfetching”
- 16. #DevSum19
- 17. #DevSum19 Why this hype? “It enables clients to specify exactly what data is needed, makes it easier to aggregate data from multiple sources, and uses a type system to describe data.”
- 19. #DevSum19 http://coolapi.com/speakers [ { "companyName": "Microsoft", "description": "Speaker, Teacher, Coder, Blogger", "id": 1, "lastName": "Hanselman", "firstName": "Scott", "position": "Program Manager“, “address” : { … }, “twitter” : “”, “github” : “”, “phoneNumber” : “” }, … ]
- 20. #DevSum19 http://coolapi.com/speakers/1 [ { "companyName": "Microsoft", "description": "Speaker, Teacher, Coder, Blogger", "id": 1, "lastName": "Hanselman", "firstName": "Scott", "position": "Program Manager“, “address” : { … }, “twitter” : “”, “github” : “”, “phoneNumber” : “” }, … ]
- 21. #DevSum19 http://coolapi.com/talks/1/speaker { "data": { "talk": { "description": "There is an entire universe outside REST apis. You just need to fly there", "title": "GraphQL", "speaker": { “firstName": “Irina" } } } }
- 22. #DevSum19 Query
- 23. #DevSum19 ▪A query is everything that can be ‘questioned’ from the outside ▪Can have headers ▪You can run multiple queries in parallel ▪You need to define the query type
- 24. #DevSum19 Querying in GraphQL { "data": { "speakers": [ { "companyName": "Microsoft", "lastName": "Hanselman", "firstName": "Scott", "twitter": “” }, … ] } } query { speakers { companyName lastName firstName twitter } }
- 25. #DevSum19 http://coolapi.com/speakers { "data": { "speakers": [ { "companyName": "Microsoft", "lastName": "Hanselman", "firstName": "Scott", "twitter": “” }, … ] } }
- 26. #DevSum19 http://coolapi.com/talks/1/speaker query { talk(id: 1) { description title speaker { lastName } } } { "data": { "talk": { "description": "There is an entire universe outside REST API. You just need to fly there", "title": "GraphQL", "speaker": { "lastName": "Hanselman" } } } }
- 27. #DevSum19 You get only data you need and nothing more
- 29. #DevSum19 ▪A Mutation is a POST, UPDATE, DELETE ▪Can have headers ▪Run one by one ▪You need to define the Input type
- 30. #DevSum19 mutation($talk: talkInput!) { createTalk(talkInput: $talk) { title description speakerId } } { "talk": { "title" :"Awesome .Net Core", "description" :"we'll talk about how cool it is .Net Core", "speakerId": 2 } } ParameterMutation
- 32. #DevSum19 ▪ Install-Package GraphQL ▪ Install-Package GraphQL.Server.Transports.AspNetCore ▪ Install-Package GraphQL.Server.Ui.Playground ▪ Add middlewares ▪ Create Schema ▪ Resolve Query ▪ Resolve Mutations Setup steps #done #NOTdone
- 33. #DevSum19
- 34. #DevSum19 ▪ your graph entities ▪ Every available query ▪ Every mutation ▪ Schema and mutations Field by Field Need to define
- 35. #DevSum19 public class ConferenceSchema : Schema { public ConferenceSchema(IDependencyResolver resolver) : base(resolver) { Query = resolver.Resolve<ConferenceQuery>(); Mutation = resolver.Resolve<ConferenceMutation>(); } } Define the schema
- 36. #DevSum19 public class Speaker : ObjectGraphType<Data.Entities.Speaker> { public Speaker() { Field(t => t.Id); Field(t => t.FirstName); Field(t => t.LastName); Field(t => t.Position).Description("The position in the company"); Field(t => t.Description).Description("Speaker Bio"); Field(t => t.CompanyName); Field(t => t.LinkedIn); Field(t => t.Twitter).Description("Twitter username"); } } Define the returned types
- 37. #DevSum19 public ConferenceQuery(SpeakersRepository speakersRepo, TalksRepository talksRepo, FeedbackService feedbackService) { Field<ListGraphType<Types.Speaker>>( "speakers", Description = "will return all the speakers", resolve: context => speakersRepo.GetAll() ); }
- 38. #DevSum19 public ConferenceMutation(TalksRepository talkRepository) { FieldAsync<Talk>( "createTalk", arguments: new QueryArguments( new QueryArgument<NonNullGraphType<TalkInput>> { Name = "talk" } ), resolve: async context => { var talk = context.GetArgument<Data.Entities.Talk>("talk"); return await context.TryAsyncResolve(async c => await talkRepository.Add(talk)); }); FieldAsync<Talk>( “updateTalk", . . . }
- 39. #DevSum19 Is GraphQL better than REST?
- 40. #DevSum19 Cool GraphQL?! ▪ When you have a REST-ish API ▪ You want to defer understanding the user needs and how the client consumes your API ▪ Easy to get started ▪ Built-in introspection ▪ Friendly ▪ Is contract-driven ▪ ‘wonderful playground’
- 41. #DevSum19 Cool GraphQL?! ▪ For small projects ▪ When you want a Gateway-like API that aggregates other Apis ▪ When you care about your consumer’s bandwith ▪ When you have no control over the client-app ▪ When you want to expose empower your consumer
- 42. #DevSum19 Problems with GraphQL? ▪ Scalability down the drain ▪ Application state is not driven by the server - > client and server are very coupled ▪ Forget about all you know in HTTP
- 43. #DevSum19 Problems with GraphQL? ▪ Single endpoint ▪ Only POST requests ▪ Caching down the drain! DataLoader
- 44. #DevSum19 DataLoader ▪ Tries to solve the n+1 problem ▪ It can batch multiple requests into one ▪ The defined name is contextual to that ‘entity’ ▪ Can ‘hold’ in memory the result of a query
- 48. #DevSum19 Don’t forget to evaluate this session in the DevSum app! #DevSum19
- 49. #DevSum19 And…. Last but not least – don’t forget to evaluate this session in the DevSum app! #DevSum19