ServerHttpResponseDecorator not work in GatewayFilter

I want to read response in GatewayFilter, I read it with ServerHttpResponseDecorator, but it not work. even can not debug into this code.

Here is my code:

@Override
    public GatewayFilter apply(Object config) {
        return (exchange, chain) -> {
            ServerHttpRequest request = exchange.getRequest();
            ServerHttpResponse response = exchange.getResponse();
            ServerHttpResponseDecorator responseDecorator = new ServerHttpResponseDecorator(response) {
                @Override
                public Mono<Void> writeWith(Publisher<? extends DataBuffer> body) {
                    if (body instanceof Flux) {
                        return super.writeWith(Flux.from(body).buffer().map(buffers -> {
                            Charset charset = response.getHeaders().getContentType().getCharset();
                            charset = charset == null ? StandardCharsets.UTF_8 : charset;
                            HttpStatus status = response.getStatusCode();

                            StringBuffer responseBody = new StringBuffer();
                            for (DataBuffer buffer : buffers) {
                                responseBody.append(DataBufferParseUtils.toString(buffer, charset));
                            }
                            log.info("Response: {}", responseBody);
                            return DataBufferParseUtils.fromString(responseBody.toString(), charset);
                        }));
                    }
                    return super.writeWith(body);
                }
            };
            return chain.filter(exchange.mutate().request(request).response(responseDecorator).build());
        };
    }