WebFlux（reactor）中获取完整response body数据

场景

使用Spring Cloud Gateway（SCG）时，想在网关日志中输出返回日志，但由于数据流只能被读取一次，必须使用特定方式进行重写才能正常返回到前端。

处理过程

• 起初使用fluxBody.map读取数据流，会出现多次输出的情况，由于使用的时reactor框架处理数据，导致会出现将一个结果集分为多次处理，会执行多次map，效果不理想。

                    Flux fluxBody = (Flux) body;
                    Mono newMono = super.writeWith(
                            fluxBody.map(dataBuffer -> {
                                String respBody = dataBuffer.toString(StandardCharsets.UTF_8);
                                if (respBody.length() > maxLogLength) {
                                    respBody = respBody.substring(0, maxLogLength);
                                }
                                if (PathUtil.checkPath(request.getPath().value(), contentLengthUrls)) {
                                    httpHeaders.setContentLength(respBody.length());
                                }
                                //匹配是否需要生成slat
                                if (PathUtil.checkPath(request.getPath().value(), loginUrls)) {
                                    String salt = createSlat(JSON.parseObject(respBody).getString("token"));
                                    if (StringUtils.isEmpty(salt)) {
                                        logger.warn("CreateSalt error:id={}", request.getHeaders().getFirst(HEADER_REQUEST_ID));
                                    } else {
                                        httpHeaders.add("s", salt);
                                    }
                                }
                                logger.info("fgwResponse : id={},body = {}", request.getHeaders().getFirst(HEADER_REQUEST_ID), respBody);
                                return bufferFactory.wrap(content);
                            })
                    );
                            //request中有salt则返回到response中
                            logger.info("fgwResponse : id={},resp = {}", request.getHeaders().getFirst(HEADER_REQUEST_ID), JSON.toJSONString(exchange.getResponse()));
                            return newMono;

• 最后查看github上的讨论，开发者给出DataBufferUtils.join(body) .doOnNext的方式。

@Component
public class LogRespFilter implements GlobalFilter, Ordered {

 	@Override
    public Mono filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        ServerHttpResponse originalResponse = exchange.getResponse();
        ServerHttpRequest request = exchange.getRequest();
        ServerHttpResponseDecorator decoratedResponse = new ServerHttpResponseDecorator(originalResponse) {
            @Override
            public Mono writeWith(Publisher body) {
            	//修改header
                HttpHeaders httpHeaders = originalResponse.getHeaders();
                httpHeaders.add("xxxxxx","aaaaaa");
                //输出返回结果
                if (body instanceof Flux) {
                    Mono newMono = super.writeWith(
                            DataBufferUtils.join(body)
                                    .doOnNext(dataBuffer -> {
                                        String respBody = dataBuffer.toString(StandardCharsets.UTF_8);
                                        //输出body
                                        logger.info("fgwResponse : body = {}", respBody);
                                    })
                    );
                    //输出response，不包含body
                    logger.info("fgwResponse : resp = {}",  JSON.toJSONString(exchange.getResponse()));
                    return newMono;

				}
				return super.writeWith(body);
            }
        };
        return chain.filter(exchange.mutate().response(decoratedResponse).build());
    }
}