Any Example for Subscriptions using graphql-java-servlet

[BharathaAravind]

I haven't found any examples for subscriptions using graphql-java-servlet. Can I get a link or example on how to use subscriptions

[wleroux]

I was able to get Subscriptions using WebSockets to work by running the example below.

Although this will work, it's not secure... WebSockets do not play nice with existing spring boot infrastructure (such as CORS/CSRF, Authentication, etc.) I opted out of this solution and focusing on making Server-Sent Events (SSE) work (#145) as these security concerns are handled by SSE.

This will create a servlet at /subscriptions that I can subscribe to:

application.xml

graphql:
  servlet:
    mapping: /graphql
    enabled: true
    websocket:
      enabled: true

GraphQL Schema Definition

type Subscription {
   echo(arg: String!): String!
}

Subscription Resolver:

@Component
class EchoController: GraphQLSubscriptionResolver {
    fun echo(arg: String): Publisher<String> {
        return Mono.just(arg)
    }
}

Client:

import ApolloClient from "apollo-client";
import { WebSocketLink } from 'apollo-link-ws'
import { HttpLink } from 'apollo-link-http'
import { split } from 'apollo-link'
import { getMainDefinition } from 'apollo-utilities';
import { InMemoryCache } from 'apollo-cache-inmemory';
import gql from "graphql-tag";

const wsLink = new WebSocketLink({
    uri: `wss://${window.location.hostname}/subscriptions`
});

const httpLink = new HttpLink({
    uri: `https://${window.location.hostname}/graphql`
});

const link = split(
    ({ query }) => {
        const { kind, operation } = getMainDefinition(query);
        return kind === 'OperationDefinition' && operation === 'subscription';
    },
    wsLink,
    httpLink,
);

const apolloClient = new ApolloClient({
    link,
    cache: new InMemoryCache()
});

const query = gql`subscription { echo(arg: "Hello") }`

apolloClient.subscribe({query: query, variables: {}}).forEach(payload => payload.data.echo)

[oliemansm]

There's an example in the samples project which also shows how to use authentication icw subscriptions: https://github.com/graphql-java-kickstart/samples/tree/master/subscription-with-authentication