Intro to GraphQL

Getting started with GraphQL!

https://tech.kakao.com/2019/08/01/graphql-basic/

https://www.slideshare.net/shilpe34/typescript-200-graphql-179690400

What is GraphQL?

Query Language for APIs!

• Query Language like SQL (Structured Query Language)

  • but, there's a big difference in linguistic structure

    • As a result, the utilization of these two is different

    • Purpose of use

      • sql : Purpose is to efficiently retrieve data stored in DB

      • gql : Purpose is for Web Client to efficiently retrieve data from server

    • Calling

      • sql : Written and called in Backend system

      • gql : Written and called in Client system

• Can load a lot of data with a single request

• Type system

• Provides powerful developer tools

Serverside GraphQL application

• Takes queries written in gql as input, processes the queries and returns the results back to client

• GraphQL server

Differences between REST API and GraphQL API

• REST API

  • Various Endpoints exist because they combine URL, METHOD, etc.

    • Database SQL query differs for each Endpoint

• gql API

  • Only one Endpoint exists

  • The type of data to load is determined through query combinations

    • Database SQL query differs for each gql schema type

The advantages and disadvantages of each change depending on the configured infrastructure, business model, and purpose of use!

schema / type

ex)

type Character {
    name: String!
    appearIn: [Episode!]!
}

• Object type : Character

• Field : name, appearIn

• Scala type : String, Id, Int etc.

• ! : Required value (non-nullable)

• [ ,] : Array

Resolver

• gql query parsing is handled by most gql libraries

  • but, the specific process of retrieving data is handled by resolver and must be implemented directly!

• If the field is a scalar value (primitive type like string or number), execution terminates

  • That is, no more chained resolver calls occur