@Component
public class MyGlobalFilter implements GlobalFilter{

    @Autowired
    WebClient.Builder builder;

@Override
public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
    ServerHttpResponse response = exchange.getResponse();
    return getFromSoap(response).switchIfEmpty(chain.filter(exchange).then(Mono.empty()))
            .flatMap(dataBuffer -> response.writeWith(Mono.just(dataBuffer)));
}

private Mono<DataBuffer> getFromSoap(ServerHttpResponse response) {
    response.setStatusCode(HttpStatus.OK);
    response.getHeaders().setContentType(MediaType.APPLICATION_JSON);
    return builder.build().get().uri("http://127.0.0.1:8080/test/list?query=11").retrieve().bodyToMono(RestResp.class).flatMap(result -> {
        if(result.isFailed()){
            return Mono.empty();
        }
        String data = JacksonUtils.toJson(result);
        return Mono.just(response.bufferFactory().wrap(data.getBytes(StandardCharsets.UTF_8)));
    });
}

}