Websocket not working with spring boot application and angular frontend - spring-boot

Question

I looked and tried a lot but I can not find the cause of my problem...
I have a JHipster generated application which consists out of a spring boot application and an angular frontend and I want to use websockets for updates. For that I use Stomp and SockJs
The connection itself is already not working.
I get the following error:
WebSocket connection to 'ws://localhost:9000/updates/websocket/447/xxudq4ni/websocket' failed: WebSocket is closed before the connection is established.
This is the call to port 9000, which is then proxied to the actual backend under Port 8080.
If I call the backend under port 8080 directly, I get:
WebSocket connection to 'ws://localhost:8080/updates/websocket/156/mg0dspp2/websocket' failed: Error during WebSocket handshake: Unexpected response code: 200
I do not really see what the actual response is but I suppose it is the JHIpster error message "an error has occured" and this html is returned with a http statuscode of 200.
I'm out of ideas what the actual problem is... I followed this intro here and several others...
here is my backend:
WebsocketConfig:
#Configuration
#EnableWebSocketMessageBroker
public class WebSocketConfig implements WebSocketMessageBrokerConfigurer {
public static final String IP_ADDRESS = "IP_ADDRESS";
#Override
public void configureMessageBroker(MessageBrokerRegistry config) {
config.enableSimpleBroker("/topic");
}
#Override
public void registerStompEndpoints(StompEndpointRegistry registry) {
registry
.addEndpoint("/updates/websocket")
//.setHandshakeHandler(defaultHandshakeHandler())
.setAllowedOrigins("*")
.withSockJS()
.setClientLibraryUrl("https://cdn.jsdelivr.net/npm/sockjs-client#1.5.0/dist/sockjs.min.js");
//.setInterceptors(httpSessionHandshakeInterceptor());
}
private DefaultHandshakeHandler defaultHandshakeHandler() {
return new DefaultHandshakeHandler() {
#Override
protected Principal determineUser(ServerHttpRequest request, WebSocketHandler wsHandler, Map<String, Object> attributes) {
Principal principal = request.getPrincipal();
if (principal == null) {
Collection<SimpleGrantedAuthority> authorities = new ArrayList<>();
authorities.add(new SimpleGrantedAuthority(AuthoritiesConstants.ANONYMOUS));
principal = new AnonymousAuthenticationToken("WebsocketConfiguration", "anonymous", authorities);
}
return principal;
}
};
}
#Bean
public HandshakeInterceptor httpSessionHandshakeInterceptor() {
return new HandshakeInterceptor() {
#Override
public boolean beforeHandshake(
ServerHttpRequest request,
ServerHttpResponse response,
WebSocketHandler wsHandler,
Map<String, Object> attributes
) throws Exception {
if (request instanceof ServletServerHttpRequest) {
ServletServerHttpRequest servletRequest = (ServletServerHttpRequest) request;
attributes.put(IP_ADDRESS, servletRequest.getRemoteAddress());
}
return true;
}
#Override
public void afterHandshake(
ServerHttpRequest request,
ServerHttpResponse response,
WebSocketHandler wsHandler,
Exception exception
) {}
};
}
}
Controller:
#Controller
public class UpdateController {
private static final Logger log = LoggerFactory.getLogger(UpdateController.class);
#MessageMapping("/updates/websocket")
#SendTo("/topic/trucks")
public UpdateDto send(UpdateDto dto) {
return dto;
}
}
Frontend:
connect(): void {
if (this.stompClient?.connected || this.called) {
return;
}
this.called = true;
// building absolute path so that websocket doesn't fail when deploying with a context path
let url = '/updates/websocket';
url = this.location.prepareExternalUrl(url);
var socket = new SockJS(url);
this.stompClient = Stomp.over(socket);
this.stompClient.connect({}, (frame) => {
this.connectionSubject.next();
this.sendActivity();
this.routerSubscription = this.router.events
.pipe(filter((event: Event) => event instanceof NavigationEnd))
.subscribe(() => this.sendActivity());
}, error => {
console.log(error);
});
}
Im on Windows and I use Chrome for the development. But it also does not work in FireFox, so I do not think it has something to do with the platform.
Any help would be very much appreciated. Thank you very much!