graphql-http

GraphQL on HTTP middleware with built-in validations and GraphQL playground

What

It provides GraphQL on HTTP middleware that can be embedded in any server.

Essentially, it takes a Request object and returns a Response object.

In the meantime, it performs HTTP request validation, processes GraphQL, and response object with the appropriate status code and message.

There is also a built-in GraphQL Playground.

Example

A simple example of creating a GraphQL server.

std/http + grpahql.js

import { graphqlHttp } from "https://deno.land/x/graphql_http@$VERSION/mod.ts";
import {
  Handler,
  serve,
  Status,
} from "https://deno.land/std@$VERSION/http/mod.ts";
import { buildSchema } from "https://esm.sh/graphql@$VERSION";

const schema = `type Query {
  hello: String!
}
`;
const graphqlResponse = graphqlHttp({
  schema: buildSchema(schema),
  rootValue: {
    hello: () => "world",
  },
  playground: true,
});

const handler: Handler = (req) => {
  const { pathname } = new URL(req.url);
  if (pathname === "/graphql") {
    return graphqlResponse(req);
  }

  return new Response("Not Found", {
    status: Status.NotFound,
  });
};

serve(handler);

Spec

This project is implemented in accordance with GraphQL over HTTP Spec.

Request Parameters

A GraphQL-over-HTTP request is formed of the following parameters:

Name	Required	Description
query	:white_check_mark:	A Document containing GraphQL Operations and Fragments to execute. Must be a string.
operationName	-	The name of the Operation in the Document to execute. GET: If present, must be a string.
variables	-	Values for any Variables defined by the Operation. GET: If present, must be represented as a URL-encoded JSON string.

Response Status

The following responses may be returned.

Status	Condition
200	If GraphQL is actually executed, even if it contains `Field errors`.
400	A required parameter does not exist. Illegal format of parameter.
405	When a mutation operation is requested on GET request.
406	The client `Accept` HTTP header does not contain at least one of the supported media types.
415	The client `Content-type` HTTP header does not contain at least one of the supported media types.
500	If the server encounters an unexpected error.

Below are the specific conditions under which each may occur. Errors are classified into four major categories.

HTTP Request errors
(GraphQL) Request errors
(GraphQL) Field errors
Unknown errors

HTTP Request errors

HTTP Request errors are errors in the http protocol. This refers to errors that can occur between HTTP and GraphQL, such as missing/incorrect values for required parameters, missing/incorrect values for required headers, etc.

Since these are client-side errors, the appropriate 4XX status is returned.

Request errors

Request errors are defined at GraphQL Spec 7.Response - Request errors.

Note here that the status code may be different depending on the Content-Type.

application/json

If Content-Type is application/json, all results of GraphQL Requests including GraphQL validation will be treated as 200 status.

See the GraphQL HTTP Spec for the reason for this.

application/graphql+json

If Content-Type is application/graphql+json, it is possible to respond with a status code other than 200 depending on the result of the GraphQL Request.

If the GraphQL request is invalid (e.g. it is malformed, or does not pass validation) then the response with 400 status code.

Field errors

Field errors are defined at GraphQL Spec 7.Response - Field errors.

Even if a Field error occurs, it will always be a 200 status code.

Unknown errors

If an error other than the above occurs on the server side, a 500 status code will be responded.

Upgrade to application/graphql+json

As you may have noticed, application/graphql+json represents a more accurate semantics response.

If you want application/graphql+json content, you must put application/graphql+json as a higher priority than application/json in the Accept header.

Example: Accept: application/graphql+json,application/json.

License

Released under the MIT license