GraphQL

Original author(s)	Facebook
Developer(s)	Open source
Initial release	September 14, 2015 (2015-09-14)
Stable release	October 2021 (2021-10)[1]
Repository	github.com/graphql/graphql-spec
Written in	Implementations in Java, JavaScript, Ruby, Scala, others.
Website	graphql.org

GraphQL is an open-source data query and manipulation language for APIs and a query runtime engine.

GraphQL enables declarative data fetching where a client can specify exactly what data it needs from an API. Instead of multiple endpoints that return separate data, a GraphQL server exposes a single endpoint and responds with precisely the data a client asked for.^[2] Because a GraphQL server can fetch from separate data sources and present the data in a unified graph, it isn't tied to any specific database or storage engine.

History

Facebook started GraphQL development in 2012 and released it as open source in 2015.^[3] In 2018, GraphQL was moved to the newly established GraphQL Foundation, hosted by the non-profit Linux Foundation.^[4][5]

On 9 February 2018, the GraphQL Schema Definition Language (SDL) became part of the specification.^[6]

Many popular public APIs adopted GraphQL as the default way to access them. These include public APIs of Facebook, GitHub, Yelp, Shopify and Google Directions API.^[7]

Design

GraphQL supports reading, writing (mutating), and subscribing to changes to data (realtime updates – commonly implemented using WebSockets).^[8] A GraphQL service is created by defining types with fields, then providing functions to resolve the data for each field. The types and fields make up what is known as the schema definition. The functions that retrieve and map the data are called resolvers.^[9]

After being validated against the schema, a GraphQL query is executed by the server. The server returns a result that mirrors the shape of the original query, typically as JSON.^[10]

type Query {
  currentUser: User
}

type User {
  id: ID!
  name: String!
}

query CurrentUser {
  currentUser {
    name
    age
  }
}

{
  "currentUser": {
    "name": "Yash Bhavsar"
    "age":23
  }
}

mutation CreateUser($name: String!, $age: Int!) {
  createUser(userName: $name, age: $age) {
    name
    age
  }
}

{
  "name": "Han Solo",
  "age": 42
}

{
  "data": {
    "createUser": {
      "name": "Han Solo",
      "age": 42
    }
  }
}

subscription {
  newPerson {
    name
    age
  }
}

{
  "newPerson": {
    "name": "Jane",
    "age": 23
  }
}

Testing

GraphQL APIs can be tested manually or with automated tools issuing GraphQL requests and verifying the correctness of the results. Automatic test generation is also possible.^[12] New requests may be produced through search-based techniques due to a typed schema and introspection capabilities.^[13]

Some of the software tools used for testing GraphQL implementations include Postman, GraphiQL, Apollo Studio, GraphQL Editor, and Step CI.^[14]

See also

• Query by Example
• OpenAPI Specification
• Microservices

References

External links

• Official website
• GraphQL: The Documentary on YouTube