Proxying STOMP over Websockets using spring-cloud-gateway-mvc - spring

Question

I am trying to have my STOMP client connect to a Websocket server over a Spring Gateway server.
My STOMP client can connect directly to the Websocket Server just fine, but i am having trouble using the gateway.
But it does not work.
I am using spring-cloud-gateway-mvc for the proxy.
Here my general purpose controller-method that does the proxying:
private final GatewayAssistant gatewayAssistant;
#RequestMapping(value = "/{service}/**")
public ResponseEntity<?> proxy(ProxyExchange<Object> proxy, #PathVariable String service, HttpServletRequest request, HttpServletResponse response) {
//Assistant method to get the correct path to the Websocket server
String path = gatewayAssistant.getUrl(proxy, service);
proxy.uri(path);
if(request.getHeader("Upgrade") != null){
path = path.replace("http", "ws"); //a temporary hack
}
//Assistant method to call the correct method, e.G if request.getMethod() is GET, it will call proxy.get()
final ResponseEntity<?> call = gatewayAssistant.call(proxy, RequestMethod.valueOf(request.getMethod()));
return call;
}
Here the Assistant class:
#Component
#RequiredArgsConstructor
public class GatewayAssistant {
private final ApplicationProperties applicationProperties;
public String getUrl(ProxyExchange<Object> proxy, String service) {
final String urlBase = applicationProperties.getGatewayPaths().get(service);
if(Objects.isNull(urlBase)) {
throw new ApplicationManagementException("No service '".concat(service).concat("' available"), HttpStatus.BAD_REQUEST);
}
final String path = proxy.path("/api/".concat(service));
return urlBase.concat(path);
}
public ResponseEntity<?> call(ProxyExchange<Object> proxy, RequestMethod method) {
return switch(method) {
case OPTIONS -> proxy.options();
case GET -> proxy.get();
case PUT -> proxy.put();
case HEAD -> proxy.head();
case POST -> proxy.post();
case PATCH -> proxy.patch();
case DELETE -> proxy.delete();
case TRACE -> throw new ApplicationManagementException("Cannot handle TRACE calls", HttpStatus.BAD_REQUEST);
};
}
}
I use simple Javascript to connect to the websocket:
let sock = new SockJS("http://my-proxy:8100/api/communication/stomp");
When i connect, then the first call gets proxied just fine, but the second call that has the "ws:" schema does not get proxied. In the WebSocket serer i get the message "Handshake failed due to invalid Upgrade header: null".
UPDATE
I get the error because use the "ws" schema. But now that i fixed that, i get no exceptions in both server, in debug logging i see no errors, yes, the front-end browser client gets "failed: Error during WebSocket handshake: Unexpected response code: 500"