I want to send image to websocket by javascript as MultipartFile

My js code

if (stompClient && stompClient.connected) {
        const imageData = document.querySelector('input[type="file"]').files;
        const formData = new FormData();
        formData.append("file", imageData[0]);

        if (imageData) {

            const message = {
                'userId': userId,
                'token': token,
                'messageType': 'PHOTO',
                'chatId': chatId,
                'file': formData // Use FormData for file upload
            };
            console.log('Sending message: ', message);
            stompClient.send("/app/messages/" + chatId, {}, JSON.stringify(message));
        } 
}

Logi

`>>> SEND
destination:/app/messages/5
content-length:111

{"userId":"4","token":"576e6e38864f4b3da266ca42baf32218617302474","messageType":"PHOTO","chatId":"5","file":{}}�`

`Sending message:  
Object { userId: "4", token: "576e6e38864f4b3da266ca42baf32218617302474", messageType: "PHOTO", chatId: "5", file: File }
file: File { name: "ziutek2.png", lastModified: 1716816552352, size: 20691, … }`

​

I don’t know how to fix that problem