@graphql-tools/url-loader

What is @graphql-tools/url-loader?

The @graphql-tools/url-loader package is designed for loading GraphQL schemas and operations over HTTP. It supports loading schemas through introspection, using GET or POST requests, and handling GraphQL operations such as queries, mutations, and subscriptions over HTTP or WebSockets. This package is part of the GraphQL Tools ecosystem, which provides a set of utilities for working with GraphQL in various environments.

What are @graphql-tools/url-loader's main functionalities?

Loading a GraphQL schema from a URL

This feature allows you to load a GraphQL schema from a remote endpoint. The `loadSchema` function uses the `UrlLoader` to fetch the schema using introspection from the provided URL.

const { loadSchema } = require('@graphql-tools/url-loader');

async function getSchema() {
  const schema = await loadSchema('http://your-graphql-endpoint.com/graphql', {
    loaders: [
      new UrlLoader()
    ]
  });
  return schema;
}

Executing a GraphQL operation using fetch

This demonstrates how to execute a GraphQL operation (query, mutation, or subscription) against a remote endpoint. The `UrlLoader` provides an `executor` function that can be used to send operations to the GraphQL server.

const { loadSchema, UrlLoader } = require('@graphql-tools/url-loader');

async function executeOperation(operation) {
  const loader = new UrlLoader();
  const executor = loader.getExecutor('http://your-graphql-endpoint.com/graphql');
  const result = await executor({
    document: operation
  });
  return result;
}

Subscribing to GraphQL subscriptions over WebSocket

This feature enables subscribing to GraphQL subscriptions using WebSockets. It leverages the `subscriptions-transport-ws` library to create a WebSocket client and then uses `createClient` from `@graphql-tools/url-loader` to handle subscriptions.

const { SubscriptionClient } = require('subscriptions-transport-ws');
const { createClient } = require('@graphql-tools/url-loader');

const wsClient = new SubscriptionClient('ws://your-graphql-endpoint.com/graphql', {
  reconnect: true
});

const client = createClient({
  url: 'http://your-graphql-endpoint.com/graphql',
  webSocketImpl: wsClient
});

const subscription = client.request({
  query: 'subscription { newData }'
}).subscribe({
  next(data) {
    console.log(data);
  }
});

Other packages similar to @graphql-tools/url-loader

apollo-link-http

Similar to @graphql-tools/url-loader, `apollo-link-http` provides capabilities to send GraphQL operations over HTTP. It is part of the Apollo ecosystem and is designed to work seamlessly with Apollo Client. However, it does not natively support loading GraphQL schemas or subscriptions over WebSockets.

graphql-request

A minimal GraphQL client for sending queries and mutations, `graphql-request` is simpler and more lightweight compared to @graphql-tools/url-loader. It does not support loading schemas or handling subscriptions, focusing instead on providing a straightforward way to execute GraphQL operations.

subscriptions-transport-ws

This package focuses specifically on handling GraphQL subscriptions over WebSockets. While @graphql-tools/url-loader supports subscriptions as part of its broader functionality, `subscriptions-transport-ws` is dedicated solely to this aspect, offering more specialized features for subscription management.