GraphQL

GraphQL is a query and manipulation language for APIs.

GraphQL Logo by Facebook is licensed under BSD

GraphQL compared to REST

A REST API client may need to make multiple calls to a REST Service to get all of the data it needs.

A GraphQL API client may be able to request all of the data it needs in a single call.

GraphQL supports reading data, mutating data, and subscribing to data (WebSockets).

server.js

We create a package.json file using the npm init command
$ npm init -y

We add the GraphQL dependencies using npm
$ npm i express@4.16.4 express-graphql@0.7.1 graphql@14.1.1 cors@2.8.5

npm i

server.js

Once the dependencies have been added we can create a server.js file.

server.js

package.json

Now we can update the package.json file and run the GraphQL service.

"scripts": {
"start": "node server.js"
},

package.json

npm start

Use "npm start" to run the GraphQL server.

$ npm start

Reading books and related author details

Reading data for a single author

Mutating data. Adding an author

Mutating data. Adding a book

A GraphQL client app

It is possible to use react and apollo to create a GraphQL client app.

We create a package.json file using the npm init command
$ npm init -y

We add the GraphQL and Apollo dependencies using npm
$ npm i apollo-boost@0.4.9 graphql@15.4.0 react@17.0.1 react-apollo@3.1.5 react-dom@17.0.1 react-scripts@4.0.1

The app.js code includes a GraphQL query, an ApolloProvider and a Query.

app.js

localhost:3000

API Gateway

Notice that the Cross-Origin Resource Sharing (CORS) library reference in the GraphQL code above is not needed when the GraphQL server and the GraphQL client App are published using an API Gateway.

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