[server side] How do I implement and expose subscriptions?

As mentioned in the question above. As far as I can tell, the resolvers for subscriptions should be implemented with the reactivestreams Publisher, but that does not seem to be the type shown in the generated interface. For example, I have

type Subscription {
    testSub: Boolean!
}

If my understanding is correct, I’m expecting to implement a Publisher<Boolean>, but right now I’m simply getting a normal Boolean return type on the interface method.

Another related question: how do I expose the necessary websockets on the server side for these subscriptions? I have tried .subscriptionExecutionStrategy(new SubscriptionExecutionStrategy()) from here but it doesn’t seem to do anything different.

Thanks!

[jxnu-liguobin]

Sorry, at first I thought you just needed to return async type.

in sbt plugin you can use option apiAsyncReturnType such as

generateAsyncApi := true
apiAsyncReturnType := "scala.concurrent.Future" //your type: Publisher

also can use in gradle plugin

generateAsyncApi = true
apiAsyncReturnType = "scala.concurrent.Future"

if resultType is Collection , use apiAsyncReturnListType

but if you want use in subscription

you can use subscriptionReturnType

like

subscriptionReturnType := Some("org.reactivestreams.Publisher")

also can use in gradle plugin

subscriptionReturnType = "org.reactivestreams.Publisher"

when you exec task, will generate java code

public interface SubscriptionResolver {

    @javax.validation.constraints.NotNull
    org.reactivestreams.Publisher<Boolean> testSub() throws Exception;

}

[fnatiq]

hi @kobylynskyi apologies for the very late reply, but thanks, I did implement the GraphQLSubscriptionResolver similarly for my testing. may I know if the websocket exposure needs to be implemented explicitly? If I understand Java correctly, websockets are implemented through http anyway, so I should think there is no further need to do anything else, but I am not able to hit the subscription WS endpoint in my GraphQL playground.

Not sure if this issue is related to the application.yml settings (I’m actually using application.properties, I understand they are basically equivalent) being only in the latest version? For my purposes, I’m currently using the codegen 2.0.0.

Would appreciate any further advice. Thank you!