The document discusses GraphQL as a powerful query language that utilizes a type system to define queries, differentiating it from REST and traditional web frameworks. It explores its integration with Groovy and Ratpack, emphasizing the benefits of faster interactions and better resource management. Additionally, it covers various aspects such as schema definition, error handling, security considerations, and best practices for using GraphQL effectively.

1. GraphQL
&
Ratpack@marioggar
1

2. Hey Hi
Mario Garcia
Twitter: @marioggar
Github: mariogarcia
Currently working for: kaleidos.net
Member of Madrid GUG
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3. Why this talk ?
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4. 3 . 1

5. Today…
GraphQL theory
GraphQL + Groovy
GraphQL + Ratpack
Summary
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6. GraphQL Theory
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7. What is GraphQL ?
Is a query language
It uses a type system to de ned those queries
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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
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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
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11. De ne Data Types
type Contestant {
name: String
}
type Raffle {
id: String
title: String
contestants: [Contestant]
noWinners: Int
}
http://facebook.github.io/graphql/
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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]
}
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13. De ne Schema
Which is the type for queries
Which is the type for mutations
type schema {
query: Query
mutation: Mutation
}
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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"
}
]
}
}
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15. Validation
raf eId was mandatory
Invalid query
type Query {
...
winners(raffleId: String!): [Contestant]
...
}
{
winners {
name
}
}
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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
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20. GOTO code
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21. Time to expose our schema
through HTTP
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22. 6 . 1

23. HTTP + GraphQL
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24. Resources vs Queries (I)
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25. Resources FrontEnd
Has to coordinate data coming from different resources
Several calls to different endpoints
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26. Resources Backend
New controller/handler for every new resource
Implement different data views
Input formal validation
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27. Resources vs Queries (II)
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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
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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
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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
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33. Documentation: GraphiQL
Single Page Application (React)
Tool for prototyping queries
Connects to a existing GraphQL/HTTP engine
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34. Documentation: Alternatives
https://nordicapis.com/10-graphql-consoles-in-action/
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35. GOTO code
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36. 7 . 1

37. Ratpack's execution model
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38. Ratpack's execution model (II)
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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
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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
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43. Error vs Exception
graphql.GraphQLError
has meaninful error data to the client
graphql.GraphQLException
has more information for developers
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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
}
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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",
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46. Error >> Exception
Throwing an exception is expensive
Returning an error is just a simple data structure
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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
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51. A good example… security
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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
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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
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58. Using REST + Instrumentation…
gql-ratpack embraces this choice
gql.ratpack.pac4j.GraphQLHandler
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59. GOTO code
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60. What is left ?
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61. 10 . 2

62. A lot but…
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63. Relay
GraphQL good practices
https://facebook.github.io/relay/
http://graphql.org/learn/best-practices/
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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 ?
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68. Thanks!
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