graphql-rest-mapper

Graphql-rest-mapper is a library for help to create a graphql wrapper for REST applications.

Under the hood, this library uses the apollo-datasource-rest. Its just a wrapping library to help you to easily integrate with existing servers. So if you wanna use this library, you need to use apollo-server.

For example, you have a REST application, either monolithic or microservices, with this library you can create a graphql data provider for these REST applications and start to use graphql in you clients now!

Its really simple to use it.

import { ApolloServer, gql } from 'apollo-server';
import { RedisCache } from 'apollo-server-cache-redis';
import { RestMapper } from 'graphql-rest-mapper';
import { mergeAll } from 'lodash/fp';
 
const routes = {
  Query: {
    getPosts: {
      url: `https://jsonplaceholder.typicode.com/posts`,
      method: 'GET',
    },
  },
};
 
const config = RestMapper(
  routes,
  ['Accept-Encoding', 'Referer', 'Origin', 'Host'],// Headers to ignore
);
 
const Query = gql`
  type Post {
    userId: Int
    id: Int
    title: String
    body: String
  }
 
  type Query {
    getPosts: [Post]!
  }
`;
 
const baseConfig = {
  typeDefs: [Query],
  cache: new RedisCache({ // OPTIONAL! But is good :)
    host: 'localhost',
  })
}
 
const apolloConfig = mergeAll([baseConfig, config]);
 
const server = new ApolloServer(apolloConfig);

Note that (type Query => getPosts) will be resolved to the Query.getPosts defined in routes. With this you can create custom field resolvers for your types!

Features

• Custom URL (url)

  Your URL can be either a string or a function. In case of function, its arguments is an object with parent and args came from resolver function.

  ({parent, args}) => `http://someendpoint/users/${args.id}`

• Custom Query String (query)

  Like custom URL, you can customize you query string to be used in the request.

  ({parent, args}) => `user=${args.id}&posts=${args.posts}`

• Custom body (body)

  In case of POST, PUT or PATCH methods, you can customize you body argument, its default value is the args argument from resolver function.

  ({parent, args}) => ({ user: args.customUser })

• Header interceptor (headerInterceptor)

  If you wanna send custom headers. NOTE: This function will override the original headers, if you return an empty object, the request will send empty headers object.

  (header) => ({ 'X-custom-header': 'ok' })

  // Append to current headers
  (header) => {
    header['X-custom-header'] = 'ok';
    return header;
  }

• Response interceptor (responseInterceptor)

  Replaces the response from external server. If the server responds something that may not complain to the required GraphQL type, but you want to pre-process the response to complain it.

  (response) => ({
    id: response.userId,
    name: response.user.name,
  })

• Ignore request headers

  This library forwards all the request headers to the calling endpoint, but you can ignore some of them, just passing an array of header names to the configuration.

  const config = RestMapper(
    routes,
    ['Accept-Encoding', 'Referer', 'Origin', 'Host'],// Headers to ignore
  );

  The above call will tells the library to ignore the "Accept-Encoding", "Referer", "Origin" and "Host" headers.