support for subscriptions

[markhamnr]

Am I wrong in thinking that subscriptions aren't supported currently?

The README implies that they are, or at least it mentions registering a Subscription class as well as a Query class and a Mutation class.

But I can't see any examples, nor can I get it to work myself. The GraphQL Java site says that a subscription should return a Publisher, but when I try that with AnnotationsSchemaCreator I get an InvalidSchemaException: "Publisher" must define one or more fields.

Is there a way to handle subscriptions I haven't figure out yet? Or if not, is this something that could be added?

[jkevan]

Hello @markhamnr,

Subscriptions are supported—we are using them in our implementation. This support is not directly related to graphql-java-annotations but rather to graphql-java. However, I agree that this specific case lacks documentation and examples.

I'll try to help:

1. WebSocket Endpoint

First, you need a WebSocket endpoint to receive subscription requests. You can find an example in our implementation:
🔗 [OsgiGraphQLWsEndpoint.java](https://github.com/Jahia/graphql-core/blob/master/graphql-dxm-provider/src/main/java/org/jahia/modules/graphql/provider/dxm/OsgiGraphQLWsEndpoint.java)

2. Base Schema Endpoint

You also need a base schema endpoint to register your subscriptions:

@GraphQLName("Subscription")
public static class Subscription {
}

3. Subscription Implementation Example

Here’s an example of a Subscription implementation:
🔗 [GqlWorkflowSubscriptionExtension.java](https://github.com/Jahia/graphql-core/blob/master/graphql-dxm-provider/src/main/java/org/jahia/modules/graphql/provider/dxm/workflow/GqlWorkflowSubscriptionExtension.java)

A key part that might be missing on your side is that the Publisher should carry a GraphQL object, like this:

Publisher<GqlWorkflowEvent>

Where GqlWorkflowEvent is a GraphQL object annotated with GraphQL annotations:

@GraphQLField
@GraphQLDescription("Workflow that has just been started")
public GqlWorkflow getStartedWorkflow() {
    return startedWorkflow;
}

Hope this helps! Feel free to explore the repository—it’s public and serves as the GraphQL API for our project. 🚀

[markhamnr]

OK, this is about the simplest example I can come up with:

https://gist.github.com/markhamnr/7a516ef640f353791165ef3f75478eae

When run, it gives me the InvalidSchemaException I mentioned above. Is there some way I can modify it to make it a valid schema?

[jkevan]

Hello, thanks you for the gist example.

Would you have the complete stack trace error ?

[Fgerthoffert]

Hi @markhamnr

Any updates on your end regarding this issue ?

Thanks

[markhamnr]

Argh, sorry I ignored this!

Here's the trace I get:

"Publisher" must define one or more fields.
	at graphql.schema.GraphQLSchema$Builder.validateSchema(GraphQLSchema.java:885)
	at graphql.schema.GraphQLSchema$Builder.buildImpl(GraphQLSchema.java:879)
	at graphql.schema.GraphQLSchema$Builder.build(GraphQLSchema.java:841)
	at graphql.annotations.AnnotationsSchemaCreator$Builder.build(AnnotationsSchemaCreator.java:266)
	at Main.main(Main.java:25)```

[jkevan]

Hi @markhamnr,

Thank you for your input. I agree that something doesn’t seem right here, but I’m not sure exactly what the issue is.

We do use subscriptions internally and have implemented them in some of our projects. However, our bandwidth to investigate community issues in the graphql-java-annotations project is currently limited, so we likely won’t be able to dig into this ourselves anytime soon.

If you’re still interested in this topic, we’d be happy to review a pull request if you’re able to investigate and propose a fix. We always make an effort to review and merge PRs as quickly as possible.

Thank you for your understanding!

Best regards