Subscription query example

Activity.kt

@Component
class ActivityProjection(
        val queryUpdateEmitter: QueryUpdateEmitter
){
  var lastActivity: Activity = ...

  @EventHandler(payloadType = OrderTakenEvent::class)
  fun onOrderTaken(event: EventMessage<OrderTakenEvent>) {
    lastActivity = Activity(
              eventId = UUID.fromString(event.identifier),
              entityId = entityId,
              activity = "Order taken")
      queryUpdateEmitter.emit(
              GetRecentActivityQuery::class.java, { query -> true }, lastActivity
      )
  }

  @QueryHandler
  fun handle(query: GetRecentActivityQuery): Activity = lastActivity

}

@RestController
@RequestMapping("/api")
class ActivityQueryController(
        val queryGateway: QueryGateway
) {
  
    @GetMapping("/activity")
    fun activity(): ResponseEntity<SseEmitter> {
        val emitter = SseEmitter()
        val subscriptionQueryResult = queryGateway.subscriptionQuery(
                GetRecentActivityQuery(),
                Activity::class.java, Activity::class.java
        )
        subscriptionQueryResult.handle({ initial ->
            emitter.send(event()
                    .id(initial.eventId.toString())
                    .data(initial, MediaType.APPLICATION_JSON)
            )
        }, { update ->
              ...
              emitter.send(
                      event()
                              .id(update.eventId.toString())
                              .data(update, MediaType.APPLICATION_JSON)
              )
             ...
        })
        ...
        return ResponseEntity.ok().headers(responseHeaders).body(emitter);
    }
}