Intercept websocket initial handshake in rsockets - spring-boot

Question

I want to be able to intercept the first request a client makes to my endpoint so to be able to answer with 101 (websocket estabilished) or deny it.
Is there any interceptor I can use? I tried registering a filter bean but it seems it is just skipped, I think because I'm in a webflux application...
#Bean
public FilterRegistrationBean<ContextFilter> initialFilter() {
FilterRegistrationBean<ContextFilter> registrationBean
= new FilterRegistrationBean<>();
registrationBean.setFilter(new MyFilter());
registrationBean.addUrlPatterns("/*");
registrationBean.setOrder(1);
return registrationBean;
}
and
public class MyFilter extends OncePerRequestFilter{
#Override
protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
throws ServletException, IOException {
log.info("You know, for filtering");
filterChain.doFilter(request, response);
}

Answer 1

To establish the RSocket connection client must send a first frame called SETUP frame. You can catch it with the Spring #ConnectMapping annotation.
#ConnectMapping
fun onConnect(rSocketRequester: RSocketRequester, clientId: String) {
if (clientId == "wrong_client") rSocketRequester.rsocket().dispose() //to reject connection
}
To reject the connection use the rSocketRequester.rsocket().dispose() as shown above.
Note that with the SETUP frame you can pass the payload and metadata from the client as usual.