What is an API?

API - Application Program Interface

What is a web API?

Web API

the part of the server that receives requests and sends responses

Most APIs are RESTful

Title Text

August 2017, source: https://jaxenter.com/state-of-api-integration-report-136342.html

Most APIs are RESTful

REST API example

REST APIs - what's wrong with them?

• Multiple Round Trips To Fetch Related Resources

• Over Fetching / Under Fetching

GraphQL the hype

• 2012 - developed internally by Facebook
• 2015 - publicly released
• 2018 - moved to GraphQL Foundation*

GraphQL history

*hosted by the non-profit Linux Foundation

GraphQL is a query language for APIs and a runtime for fulfilling those queries with your existing data. *

*official definition from https://graphql.org

What is GraphQL?

1. Define types and fields:

How GraphQL works?

2. Provide function for each field on each type

How GraphQL works?

3. Run a graph service:

How GraphQL works?

• usually a web service at a URL
• single endpoint
• has many differnt server implementations: C#, Go, Java, Python, Ruby, Clojure, JavaScript, PHP and more

4. Run a query:

The server:

• checks to ensure it only refers to the types and fields defined
• runs the provided functions to produce a result
• query == read or write operation

How GraphQL works?

4. Run a query:

How GraphQL works?

{
  me {
    name
  }
}

{
  "me": {
    "name": "Luke Skywalker"
  }
}

JSON result

Example query

Ask for a specific field -> get the same shape as result

GraphQL queries 

Query objects

GraphQL queries 

Arguments

GraphQL queries 

Aliases to rename the result

GraphQL queries 

1. Ask for a specific field -> get the same shape as result

GraphQL queries 

Fragments - reusable sets of query fields

GraphQL queries 

GraphQL queries 

Explicit operation name

Operation == query or mutation or subscription 

Variables for dynamic queries

GraphQL queries 

Directives

GraphQL queries 

Mutations

GraphQL queries 

GraphQL schemas and types 

Object types

type Starship {
  id: ID!
  name: String!
  length(unit: LengthUnit = METER): Float

  appearsIn: [Episode!]!
}

GraphQL schemas and types 

Scalar types:

• Int
• Float
• String
• Boolean
• ID - object/cache
• can implement custom scalar types*

GraphQL schemas and types 

Enum Types:

GraphQL schemas and types 

Interfaces

GraphQL schemas and types 

Union

Authorization -> business logic layer

GraphQL

GraphQL pros 

• no need to do multiple round trips to fetch data
• a request language: less client-server dependency, no hardcoded data size and shape
• express data requirements in a declarative way

GraphQL cons

• introducing another dependency to the project
• resource exhaustion attack (DoS attack)
• authentication and authorization - do we handle them before, after, or during a GraphQL resolve process?
• RESTful APIs are easier to cache
• N+1 SQL queries

Who is using GraphQL?

GraphQL 

and more https://graphql.org/users/

GraphQL Editor