Slides of my presentation at https://gr8conf.eu/ about developing GraphQL applications with Groovy and Ratpack (https://ratpack.io/)

1. GraphQL
&
Ratpack@marioggar
1

2. Hey Hi
Mario Garcia
Twitter: @marioggar
Github: mariogarcia
Currently working for: kaleidos.net
Member of Madrid GUG
2 . 1

3. Why this talk ?
2 . 2

4. 3 . 1

5. Today…
GraphQL theory
GraphQL + Groovy
GraphQL + Ratpack
Summary
3 . 2

6. GraphQL Theory
4 . 1

7. What is GraphQL ?
Is a query language
It uses a type system to de ned those queries
4 . 2

8. What is NOT ?
It’s not a web framework
It doesn’t have to do with HTTP necessarily
And de nitely…
GraphQL is not REST
4 . 3

9. 5 . 1

10. To exec your 1st GraphQL query
De ne Data Types
De ne Query Types
De ne Schema
Execute queries against the de ned schema
5 . 2

11. De ne Data Types
type Contestant {
name: String
}
type Raffle {
id: String
title: String
contestants: [Contestant]
noWinners: Int
}
http://facebook.github.io/graphql/
5 . 3

12. De ne Queries
Query is just another type
It de nes all possible queries over de ned types
Queries can use other types or scalars
Queries may have arguments
type Query {
list: [Raffle]
getWinners(raffleId: String!): [Contestant]
}
5 . 4

13. De ne Schema
Which is the type for queries
Which is the type for mutations
type schema {
query: Query
mutation: Mutation
}
5 . 5

14. Execute a query
query: "give me (id, title) of all raf es
result: list of available raf es
{
list {
id
title
}
}
{
"data": {
"list": [
{
"id": "pfoqjfq09w8jf",
"title": "A Greach T-Shirt"
}
]
}
}
5 . 6

15. Validation
raf eId was mandatory
Invalid query
type Query {
...
winners(raffleId: String!): [Contestant]
...
}
{
winners {
name
}
}
5 . 7

16. 5 . 8

17. GraphQL and JVM
https://github.com/graphql-java
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18. 5 . 10

19. First Groovy example
Execute a simple query
GQL ( )
DSL on top of
https://github.com/grooviter/gql
GraphQL-Java
5 . 11

20. GOTO code
5 . 12

21. Time to expose our schema
through HTTP
5 . 13

22. 6 . 1

23. HTTP + GraphQL
6 . 2

24. Resources vs Queries (I)
6 . 3

25. Resources FrontEnd
Has to coordinate data coming from different resources
Several calls to different endpoints
6 . 4

26. Resources Backend
New controller/handler for every new resource
Implement different data views
Input formal validation
6 . 5

27. Resources vs Queries (II)
6 . 6

28. Faster interaction w Front End
Queries and Mutations can be batched
Queries are executed in parallel
No more controllers / handlers
GraphQL engine takes care of input formal validation
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29. 6 . 8

30. Ratpack + GraphQL
http://ratpack.io
6 . 9

31. Why Ratpack ?
Is lightweight
It is a lean and powerful foundation, not an all-
encompassing framework.
Very good performance
Netty + Ratpack’s execution model
6 . 10

32. Exposing GraphQL with Ratpack
gql-ratpack
Module of GQL project
It provides:
GraphQL endpoint
G hiQ l
https://grooviter.github.io/gql/docs/html5/index.html#_ratpack
6 . 11

33. Documentation: GraphiQL
Single Page Application (React)
Tool for prototyping queries
Connects to a existing GraphQL/HTTP engine
6 . 12

34. Documentation: Alternatives
https://nordicapis.com/10-graphql-consoles-in-action/
6 . 13

35. GOTO code
6 . 14

36. 7 . 1

37. Ratpack's execution model
7 . 2

38. Ratpack's execution model (II)
7 . 3

39. Honor Ratpack's executors
CompletableFuture can be used as a service return type
Access executors via ratpack.exec.Execution
Execute CompletableFuture using the proper executor
Create your own abstractions
7 . 4

40. Abstractions
@Override
CompletableFuture<List<Map>> listCookies(DataFetchingEnvironment env) {
Selectors.ListCookiesParams params = Selectors.listCookiesParams(env)
return Futures.blocking { // <-- blocking operation
repository.list(params)
}
}
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41. 8 . 1

42. Error Handling
REST ⇒ HTTP codes
GraphQL ⇒ rich messages
8 . 2

43. Error vs Exception
graphql.GraphQLError
has meaninful error data to the client
graphql.GraphQLException
has more information for developers
8 . 3

44. Error
{
"data": null,
"errors": [
{
"message": "Validation error of type MissingFieldArgument: Missing
"locations": [
{
"line": 2,
"column": 3
}
],
"description": "Missing field argument raffleId",
"validationErrorType": "MissingFieldArgument",
"errorType": "ValidationError",
"path": null,
"extensions": null
}
8 . 4

45. Exception
{
"data": {
"winners": null
},
"errors": [
{
"message": "Exception while fetching data (/winners) : null",
"path": [
"winners"
],
"exception": {
"cause": {
"cause": null,
"stackTrace": [
{
"methodName": "newInstance0",
"fileName": "NativeConstructorAccessorImpl.java",
8 . 5

46. Error >> Exception
Throwing an exception is expensive
Returning an error is just a simple data structure
8 . 6

47. Error >> Exception (II)
You need to be aware of instrumentations
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48. 8 . 8

49. Instrumentations
Middleware executed before/after elds and data fetchers
Error handling, security, tracing… you name it!
Can be chained
Can modify the behavior of the execution ow
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50. Instrumentations
8 . 10

51. A good example… security
8 . 11

52. 9 . 1

53. Security
Did I mention that GraphQL is a query language ?
It knows nothing about security mechanisms
We have to make the engine aware of security…
Using the Context
9 . 2

54. Context
Can carry information from outside to the GraphQL
execution ow
Can be any type of data structure (Map, List…)
Available through all the execution ow (instrumentations
and data fetchers)
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55. Two strategies
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56. Using Instrumentation
More control
Harder to integrate with Ratpack’s execution model
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57. Using REST + Instrumentation
You can use already implemented integrations (Pac4j)
Easier to integrate with Ratpack’s execution runtime
9 . 6

58. Using REST + Instrumentation…
gql-ratpack embraces this choice
gql.ratpack.pac4j.GraphQLHandler
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59. GOTO code
9 . 8

60. What is left ?
10 . 1

61. 10 . 2

62. A lot but…
10 . 3

63. Relay
GraphQL good practices
https://facebook.github.io/relay/
http://graphql.org/learn/best-practices/
10 . 4

64. Alternatives to Ratpack + GQL
gorm-graphql with/without Grails, Micronaut…
If you like GORM, and ts your plan, use it!
graphql-java
DIY
https://github.com/grails/gorm-graphql
h // h l j d h d i / /l / 10 . 5

65. 11 . 1

66. Summary: GraphQL
Is not a silver bullet
Is an improvement between back/front
GraphQL It’s not limited to HTTP
As a query language, is still underestimated
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67. Questions ?
11 . 3

68. Thanks!
11 . 4