GraphQL with Kotlin

How to query and build a schema with GraphQL using Kotlin.

Transcript

1. GraphQL +Kotlin
   Mohit Sarveiya
   

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2. — Query Language for your API developed at Facebook.
   — Polyglot implementation for client and server - Java, Javascript,
   Python, etc…
   — Reduces API requests needed and only gives you that data you
   asked for.
   What is GraphQL?
   

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3. Problem
   — Too many API requests per month.
   — Would be good to get data for a 

   month in request.
   

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4. GraphQL Overview
   query GetMonthData {
   campaign {
   date range
   posts {
   title
   created date
   }
   …
   }
   }
   Return Result
   Fetches Data
   Validates
   Client Server
   

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5. GraphQL Overview
   query GetMonthData {
   campaigns {
   title
   posts {
   title
   }
   …
   }
   }
   Return Result
   Fetches Data
   Validates
   Query Result
   {
   campaigns {
   [ {
   title: “Campaign 1”
   posts: [
   title: “Post 1”
   ]
   } …
   ]
   }
   }
   

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6. DATABASE
   REST API
   CLIENTS
   GraphQL Server
   

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7. DATABASE
   REST API
   GRAPHQL SERVER
   CLIENTS
   GraphQL Server
   

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8. 1. How to query the sever
   2. Build a GraphQL server
   in Kotlin
   

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9. Star Wars Database
   Droids (R2D2, C3PO,…)
   — name, height, friends, 

   primary function..
   Humans (Luke, Leia, Solo,…)
   — name, height, friends, planet…
   

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10. Simple Query
    query Hero {
    hero {
    name
    }
    }
    

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11. Simple Query
    query Hero {
    hero {
    name
    }
    }
    GraphQL Object defined in schema.
    Field on hero object.
    

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12. Simple Query
    query Hero {
    hero {
    name
    }
    }
    {
    data: {
    hero: {
    name: “R2 -D2”
    }
    }
    }
    Query Result
    

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13. 1. How to construct queries on
    Android in Kotlin
    

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15. 1. Add Gradle Plugin.
    2. Add schema definition to app in a JSON file.
    3. Add queries to files with a “.graphql” file extension.
    4. Use autogenerate classes from the “.graphql” files to make calls.
    Integrating Apollo Android Client
    

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16. 1. Add Apollo Gradle Plugin
    

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17. 2. Add Introspection of Schema (schema.json)
    

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18. 3. Add Queries to file with “.graphql” ext
    File: queries.graphql
    

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19. 4. Use ApolloClient object to make request
    

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20. Arguments & Variables
    

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21. Get Details for Droid with id - 2000.
    

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22. Get Details for Droid for any id
    

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23. Handling arguments on Android
    

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24. Result
    Query
    

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25. Enum Arguments
    

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26. Supplying Enum Arguments on Android
    

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27. Aliases & Fragments
    

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28. Aliases
    

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29. Aliases
    

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30. Aliases
    

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31. Aliases
    

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32. Fragments
    

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33. Fragments
    

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34. Fragments
    

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35. Mutations
    

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36. Create a Review for an Episode
    

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37. Mutating on Android
    

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38. Mutation Result
    

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39. 2. Building a GraphQL server
    

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42. — GraphQL Object type
    — Scalar types (String, Int, Float, Boolean)
    — List type
    — Interface type
    — Enum type
    — Union type
    — Input Object type
    GraphQL Type System
    

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43. Star Wars Database
    Droids (R2D2, C3PO,…)
    — name, height, friends, 

    primary function..
    Humans (Luke, Leia, Solo,…)
    — name, height, friends, planet…
    

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44. — Common fields between Human and Droid
    — name
    — height
    — friends
    — appearsIn
    Create an interface
    

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45. Character Interface
    

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46. Droid GraphQL Object
    

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47. Human GraphQL Object
    

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48. Enum Types
    

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49. Schema Structure
    

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50. Query Type
    

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51. Parsing Queries and Returning Results
    

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53. — Client and server Java GraphQL implementations are not stable.
    — No Kotlin only GraphQL implementation.
    — Learning curve.
    — Need to setup GraphQL server on top of your infrastructure. This
    requires more work.
    Disadvantages
    

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54. Thanks! May the force be with
    you!
    Twitter: @heyitsmohit
    Github: http://github.com/mysa
    

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