HTTP Link

Purpose

An Apollo Link to allow sending a single http request per operation.

Installation

npm install apollo-angular-link-http --save

Usage

import { HttpLinkModule, HttpLink } from 'apollo-angular-link-http';


@NgModule({
  imports: [
    HttpLinkModule
  ]
})
class AppModule {
  constructor(httpLink: HttpLink) {
    const link = httpLink.create({ uri: '/graphql' });
  }
}

HttpClient

The HTTP Link relies on having HttpClient (from @angular/common/http) present in your application.

Options

HTTP Link takes an object with some options on it to customize the behavior of the link. If your server supports it, the HTTP link can also send over metadata about the request in the extensions field. To enable this, pass includeExtensions as true. If you would like to use persisted queries or just not to send a query, disable includeQuery.

|name|value|default|required| |---|---|---|---| |uri|string|/graphql|false| |includeExtensions|boolean|false|false| |includeQuery|boolean|true|false| |headers|HttpHeaders|none|false| |withCredentials|boolean|none|false| |method|string|POST|false|

Context

The HTTP Link uses the headers field on the context to allow passing headers to the HTTP request. It also supports the withCredentials field for defining credentials policy for request. These options will override the same key if passed when creating the the link. If some setting is different than the one in Options, this one will be used.

|name|value|default|required| |---|---|---|---| |uri|string|as in options|false| |includeExtensions|boolean|as in options|false| |includeQuery|boolean|as in options|false| |headers|HttpHeaders|none|false| |withCredentials|boolean|as in options|false| |method|string|as in options|false|

import { HttpLinkModule, HttpLink } from 'apollo-link-http';
import { ApolloModule, Apollo } from 'apollo-angular';
import { InMemoryCache } from 'apollo-cache-inmemory';
import { HttpClientModule } from '@angular/common/http';

@NgModules({
  imports: [
    HttpClientModule,
    ApolloModule,
    HttpLinkModule
  ]
})
class AppModule {
  constructor(
    apollo: Apollo,
    httpLink: httpLink
  ) {
    apollo.create({
      link: httpLink.create({ uri: '/graphql' }),
      cache: new InMemoryCache()
    });
  }
}

// a query with apollo-angular
apollo.query({
  query: MY_QUERY,
  context: {
    // example of setting the headers with context per operation
    headers: new HttpHeaders().set('X-Custom-Header', 'custom-value')
  }
})

Middleware

import { ApolloLink } from 'apollo-link';
import { HttpLink } from 'apollo-angular-link-http';

class AppModule {
  constructor(httpLink: HttpLink) {
    const http = httpLink.create({ uri: '/graphql' });
    const middleware = new ApolloLink((operation, forward) => {
      operation.setContext({
        headers: new HttpHeaders().set('Authorization', localStorage.getItem('token') || null)
      });
      return forward(operation)
    })

    const link = middleware.concat(http);
  }
}

Afterware (error)

import { ApolloLink } from 'apollo-link';
import { HttpLink } from 'apollo-angular-link-http';
import { onError } from 'apollo-link-error';

import { Auth } from './auth.service';

class AppModule {
  constructor(
    httpLink: HttpLink,
    auth: Auth
  ) {
    const http = httpLink.create({ uri: '/graphql' });
    const error = onError(({ networkError }) => {
      if (networkError.status === 401) {
        auth.logout();
      }
    })

    const link = error.concat(httpLink);
  }
}