Most developers are familiar with making network requests using RESTFUL APIs. However, there are some disadvantages to this approach: very coupling between the backend and the client. For instance, they must communicate back with the backend team when a mobile client wants to change or add some fields to the response. The time for discussions among teams and service deployment might delay project deadlines, hence affecting business opportunities. This topic will discuss the newer approach, GraphQL, and how to apply libraries to the Android world to solve this problem.

1. GraphQL in Android
Thao Huynh Quang
Trusting Social

2. Restful Service

3. Restful Service
- Using JSON Format.

4. Restful Service
- Using JSON Format.
- Human readable and editable.

5. Restful Service
- Using JSON Format.
- Human readable and editable.
- There are many libraries supporting Restful Service

6. Restful Service
- Using JSON Format.
- Human readable and editable.
- There are many libraries supporting Restful Service
- There are many tools supporting Restful Service.

8. Issue 1: Multiple round trips
Requirements:
- Get all the feeds
- Display Jirst comment at every feed

9. Issue 1: Multiple round trips
Requirements:
- Get all the feeds
- Display Jirst comment at every feed
Solution 1:
- get_all_feeds(user_name, offset, limit)
- get_comments_by_feed_id(feed_id, total_comment)

10. Issue 1: Multiple round trips
Requirements:
- Get all the feeds
- Display Jirst comment at every feed
Solution 1:
- get_all_feeds(user_name, offset, limit)
- get_comments_by_feed_id(feed_id, total_comment)
10 items/page: 11 requests. (N+1 query problem)

11. Issue 1: Multiple round trips
Solution 2:
- get_all_feeds(user_name, offset, limit)
Return Jirst comment for every feed item.

12. Issue 1: Multiple round trips
Solution 2:
- get_all_feeds(user_name, offset, limit)
Return Jirst comment for every feed item.
New requirements:
- Get all the feeds
- Display Jirst comment at every feed on web.
- Display no comment on mobile device.

13. Issue 1: Multiple round trips
Solution 2:
- get_all_feeds(user_name, offset, limit)
Return Jirst comment for every feed item.
New requirements:
- Get all the feeds
- Display Jirst comment at every feed on web.
- Display no comment on mobile device.
Solution:
- get_feeds_for_mobile and get_feeds_for_web
- get_feeds(user_name, offset, limit, total_comment)

14. Issue 1: Multiple round trips
Problem: REST resource that is too tightly-couple to client UI

15. Issue 2: Keeping backward compatible
New requirements:
- Get all the feeds
- Remove total views. It is so distract for users.
Old requirements:
- Get all the feeds
- Display total views at every feed

16. Issue 2: Keeping backward compatible
- Solution 1: remove total_views: old client will be broken.
- Solution 2: keep total_views: bloating api
- Solution 3: making new api. Increasing maintain cost.
…

17. Issues 3: Over fetching of data
- Mobile: feed doesn’t need to show the created date.
- Web: feed need to show the created date.

18. Problems
- Client can get only data which server has deJined.
- Many different types of client (Android, iOS, Web …)
- Client changes overtime.

19. Problem
Can client query directly to server ?

20. Problem
Can client query directly to server ?

22. GraphQL

23. Introduction
GraphQL is an open-source data query and manipulation language for APIs,
and a runtime for fulJilling queries with existing data.
GraphQL was developed internally by Facebookin 2012 before being publicly
released in 2015.

24. Introduction

25. Introduction
Speci?ication…NOT Implementation
GraphQL is a query language, it is a way to get data from an API to your application hence.

26. Introduction
Speci?ication…NOT Implementation
GraphQL is a query language, it is a way to get data from an API to your application hence.
Cooperation between server side and client side
Server must deJines all necessary APIs
Client should have supported GraphQL for querying.

27. Introduction
Speci?ication…NOT Implementation
GraphQL is a query language, it is a way to get data from an API to your application hence.
Cooperation between server side and client side
Server must deJines all necessary APIs
Client should have supported GraphQL for querying.
Multiple platforms
Android, iOS, Web

28. GraphQL Language

29. Query Data

30. Query Data

31. Filter & Paging

32. Relationship

33. GraphQL vs Restful

36. Companies

37. Companies

38. Restful over GraphQL
- Tooling
- Caching
- Query performance
- Limited languages
- …

39. Step-by-Step
Android

40. Library
Bad news: Facebook does not open source Android GraphQL client

41. Library
Bad news: Facebook does not open source Android GraphQL client
Good news: Apollo Android Client
Developed by Shopify, New York Times and AirBnB

42. Library
Bad news: Facebook does not open source Android GraphQL client
Good news: Apollo Android Client
Developed by Shopify, New York Times and AirBnB

43. Step 1: Setup Apollo dependencies
Just follow on https://github.com/apollographql/apollo-android

44. Step 2: DeJine graphQL query
Import schema
DeJine GraphQL query
Compile

45. Step 2: DeJine graphQL query
FeedQuery feedQuery = FeedQuery.builder()
.limit(10)
.type(FeedType.HOT)
.build()

46. Step 3: Consume
private static final String BASE_URL = "<your_server>/graphql";
OkHttpClient okHttpClient = new OkHttpClient.Builder().build();
ApolloClient apolloClient = ApolloClient.builder()
.serverUrl(BASE_URL)
.okHttpClient(okHttpClient)
.build();

47. Step 3: Consume
apolloClient.query(feedQuery).enqueue(new
ApolloCall.Callback<FeedQuery.Data>() {
@Override public void onResponse(@NotNull Response<FeedQuery.Data>
dataResponse) {
});
}
@Override public void onFailure(@NotNull Throwable t) {
}
});

48. References
Repos: https://github.com/hqthao/graphql_demo

49. References
https://github.com/apollographql/apollo-android
https://graphql.org/learn/
https://github.com/graphql/graphql-spec
https://www.howtographql.com/

50. Q&A