GraphQL Express Middleware

Create a GraphQL HTTP server with Express.

npm install --save express-graphql

Install express-graphql as middleware in your express server:

var graphqlHTTP = require('express-graphql');

var app = express();

app.use('/graphql', graphqlHTTP({ schema: MyGraphQLSchema }));

Options

The graphqlHTTP function accepts the following options:

• schema: A GraphQLSchema instance from graphql-js. A schema must be provided.

• rootValue: A value to pass as the rootValue to the graphql() function from graphql-js.

• pretty: If true, any JSON response will be pretty-printed.

HTTP Usage

Once installed at a path, express-graphql will accept requests with the parameters:

• query: A string GraphQL document to be executed.

• variables: The runtime values to use for any GraphQL query variables as a JSON object.

• operationName: If the provided query contains multiple named operations, this specifies which operation should be executed. If not provided, an 400 error will be returned if the query contains multiple named operations.

GraphQL will first look for each parameter in the URL's query-string:

/graphql?query=query+getUser($id:ID){user(id:$id){name}}&variables={"id":"4"}

If not found in the query-string, it will look in the POST request body.

If a previous middleware has already parsed the POST body, the request.body value will be used. Use multer or a similar middleware to add support for multipart/form-data content, which may be useful for GraphQL mutations involving uploading files.

If the POST body has not yet been parsed, graphql-express will interpret it depending on the provided Content-Type header.

• application/json: the POST body will be parsed as a JSON object of parameters.

• application/x-www-form-urlencoded: this POST body will be parsed as a url-encoded string of key-value pairs.

• application/graphql: The POST body will be parsed as GraphQL query string, which provides the query parameter.

Advanced Options

In order to support advanced scenarios such as installing a GraphQL server on a dynamic endpoint or accessing the current authentication information, graphql-express allows options to be provided as a function of each express request.

This example uses express-session to run GraphQL on a rootValue based on the currently logged-in session.

var session = require('express-session');
var graphqlHTTP = require('express-graphql');

var app = express();

app.use(session({ secret: 'keyboard cat', cookie: { maxAge: 60000 }}));

app.use('/graphql', graphqlHTTP(request => ({
  schema: MySessionAwareGraphQLSchema,
  rootValue: request.session
})));