RestEndpoint.kt

@Controller
class RestEndpoint {

    @Autowired
    lateinit var dataProvider: DataProvider

    @GetMapping("/cars/sse")
    fun getSseCars(response: HttpServletResponse): SseEmitter {
        val emitter = SseEmitter()
        dataProvider.getDataStream().subscribe({
            emitter.send(SseEmitter.event().data(Klaxon().toJsonString(it), MediaType.APPLICATION_JSON))
        }, ::println, {
            emitter.send(SseEmitter.event().data("done"))
            emitter.complete()
        })
        return emitter
    }
}