How can i simulteaneosly post a multipart form and receive Server sent event notifications with Springboot and react

Question

I am trying to upload a file from a react frontend to a springboot backend, whilst this is working well when i try to intergrate server sent event notifications i get the following problems. If i include the content type "text/event-stream" header i get an error that my request is no longer a multipart request and if i exclude the header completely i do not receive the notifications.

My front end:

function uploadFile(file){

    const sse = new EventSource(`${apiConstants.API_BASE_URL}/api/uploadFile`,{ withCredentials: false });

    function getRealtimeData(data) {
        console.log(data)
    }

    sse.onmessage = e => getRealtimeData(e.data);
    sse.onerror = (e) => {
        // error log here
        console.log(e)
        sse.close();
    }
    const requestOptions = {
        method: 'POST',
        headers: {
           // "Content-Type": "text/event-stream",

            ...authHeader()
        },
        body:file
    };

    return fetch(`${apiConstants.API_BASE_URL}/api/UploadFile`, requestOptions)
        .then(handleProgressResponse)
        .then(response => {
            return response;
        });
}

function handleProgressResponse(response) {
    console.log(response)
    return response.text().then(text => {
        console.log(text)
        const data = text ;

        if (!response.ok){
            if (response.status === 401) {
                logout();
            }
            return Promise.reject(data);
        }

        return data;
    })
}

my backend :

@RequestMapping("/api/UploadFile")
    public SseEmitter  UploadFile(@RequestParam("file") MultipartFile file) {
        // validate file
        final SseEmitter emitter = new SseEmitter(10000000L);
        if (file.isEmpty()) {
            emitter.completeWithError(new Exception("File is Empty Please try again"));
        } else {
            return UploadFile(file,emitter);
        }
        return emitter;
    }