Subscriptions

To see more details on how to implement subscriptions in your schema, see the schema generator docs on executing subscriptions. This page lists the graphql-kotlin-spring-server specific features.

Flow Support

graphql-kotlin-spring-server provides automatic support for Kotlin Flow by automatically configuring FlowSubscriptionSchemaGeneratorHooks and FlowSubscriptionExecutionStrategy beans.

info

If you define your subscriptions using Kotlin Flow, make sure to extend FlowSubscriptionSchemaGeneratorHooks whenever you need to provide some custom hooks.

Subscription Protocols

graphql-transport-ws subprotocol

We have implemented subscriptions in Spring WebSockets following the graphql-transport-ws subprotocol from The Guild. This requires that your client send and parse messages in a specific format. See protocol documentation for expected messages.

graphql-transport-ws is the default subscription protocol that is enabled by default.

(deprecated) subscriptions-transport-ws subprotocol

caution

subscriptions-transport-ws was deprecated in favor of graphql-transport-ws protocol.

We have implemented subscriptions in Spring WebSockets following the subscriptions-transport-ws subprotocol defined by Apollo. This requires that your client send and parse messages in a specific format. See protocol documentation for expected messages.

subscription-transport-ws is deprecated. In order to use it, you need to explicitly opt-in by specifying graphql.subscriptions.protocol=APOLLO_SUBSCRIPTIONS_WS configuration property. Support for this protocol will be removed in the next major release.

Subscription Hooks

In line with the Apollo protocol, we have implemented hooks to execute functions at different stages of the connection lifecycle. If you would like to implement your own subscription hooks, you can provide a primary spring bean for ApolloSubscriptionHooks that overrides the default one which do not perform any actions.

onConnect / onConnectWithContext

Allows validation of connectionParams prior to starting the connection. You can reject the connection by throwing an exception. If you need to forward state to execution, update and return the GraphQLContext.

onOperation / onOperationWithContext

Called when the client executes a GraphQL operation. The context can not be updated here, it is read only.

onOperationComplete

Called when client's unsubscribes

onDisconnect

Called when the client disconnects

Example

You can see an example implementation of a Subscription in the example app.