SimpleWebSocketHandler.java

@Configuration
@EnableWebFlux
@Slf4j
public class SimpleWebSocketHandler implements WebSocketHandler {

    @Bean
    public SimpleUrlHandlerMapping simpleUrlHandlerMapping() {
        Map<String, WebSocketHandler> urlMap = new HashMap<>();
        urlMap.put("/ws", this::handle);

        SimpleUrlHandlerMapping handlerMapping = new SimpleUrlHandlerMapping();
        handlerMapping.setUrlMap(urlMap);
        handlerMapping.setOrder(1);

        return handlerMapping;
    }

    @Override
    public Mono<Void> handle(WebSocketSession session) {
        UriComponentsBuilder builder = UriComponentsBuilder.fromUri(session.getHandshakeInfo().getUri());
        Map<String,String> queryParams = builder.build().getQueryParams().toSingleValueMap();
        String uniqueId = queryParams.get("email");
        log.info("Websocket connected for id "+uniqueId);
        Flux<WebSocketMessage> messageFlux = session.receive()
                .map(msg -> "Server received: " + msg.getPayloadAsText())
                .map(session::textMessage);

        return session.send(messageFlux);
    }
}