How do I get EventSource.onmessage to work?

How do I get EventSource.onmessage to work?

Here is my subscribe and pushevent code:

    public SseEmitter subscribe() throws Exception {
        SseEmitter emitter = new SseEmitter(1800000L);

        emitters.add(emitter);

        emitter.onCompletion(() -> {
            synchronized (emitters) {
                emitters.remove(emitter);
            }
        });
        emitter.onTimeout(() -> {
            emitter.complete();
            emitters.remove(emitter);
        });

        return emitter;
    }

    @Async
    public void pushEventMap(Map<String, Object> pushMap) throws IOException {
        List<SseEmitter> deadEmitters = new ArrayList<>();

        HashMap<String,Object> map = (HashMap<String,Object>) pushMap;

        emitters.forEach(emitter -> {
            try {
                emitter.send(SseEmitter.event().name("myEvent").data(map));
            } catch (Exception e) {
                emitter.completeWithError(e);
                logger_error.error("pushEvent Exception:" + e);
                deadEmitters.add(emitter);
            }
        });
        emitters.removeAll(deadEmitters);
    }

The controller for the above service is:

   @RequestMapping(value = "/subscribe", produces = "text/event-stream")
    public ResponseEntity<SseEmitter> subscribe() throws Exception {

        final SseEmitter emitter = eventService.subscribe();

        return new ResponseEntity<>(emitter, HttpStatus.OK);
    }

    @RequestMapping(value = "/publish")
    public void publish() throws IOException {
        eventService.pushEventMap(pushMap);
    }

I want the client to receive the data of event push through js.

const eventInit = () => {

    console.log("eventInit called");
    const url = 'http://localhost:8080/itf/subscribe';
    const eventSource = new EventSource(url);

    var httpRequest = new XMLHttpRequest();

    eventSource.onmessage = (event) => {
        const data = JSON.parse(event.data);
        console.log('===');
        console.log(data);

    }
    eventSource.onopen = (event) => {
        console.log('sse open');
        console.log(event);
    }

    eventSource.onerror = (event) => {
        if (event.readyState == EventSource.CLOSED) {
            console.log('sse close');
        } else {
            console.log("onerror", e);
        }
    }

}

In this state, if I send event-generating data through postman, sse open appears on the console.

However, the result of the event is not displayed.

If I directly access /itf/subscribe through the url, the result of the event is displayed on the screen. However, I am not receiving the result of the event through event.onmessage.

What I want is to raise an event, and then receive the result of the event through the onmessage function.

I am wondering how can I get the result of the event.

best regards