（1）一开始搜索读取参数的文章，方法大多是从body里读一次DataBuffer，转成字符串，然后再把字符串转成DataBuffer重新放到body里，如：

（2）

上面的方法我试过可以，但是Content-Type是multipart/form-data的时候会报错java.lang.IllegalStateException: Only one connection receive subscriber allowed.不知道是不是我姿势不对。而且如果我们在代理到第三方服务的时候才读取body，这样效率应该会高一些看NettyRoutingFilter类里的filter方法public Mono
    
      filter(ServerWebExchange exchange, GatewayFilterChain chain) {        ·······        Mono
     
       responseMono = this.httpClient.request(method, url, req -> {            final HttpClientRequest proxyRequest = req.options(NettyPipeline.SendOptions::flushOnEach)                    .headers(httpHeaders)                    .chunkedTransfer(chunkedTransfer)                    .failOnServerError(false)                    .failOnClientError(false);            if (preserveHost) {                String host = request.getHeaders().getFirst(HttpHeaders.HOST);                proxyRequest.header(HttpHeaders.HOST, host);            }            if (properties.getResponseTimeout() != null) {                proxyRequest.context(ctx -> ctx.addHandlerFirst(                        new ReadTimeoutHandler(properties.getResponseTimeout().toMillis(), TimeUnit.MILLISECONDS)));            }            return proxyRequest.sendHeaders()                     //这里的是ReactorServerHttpRequest调用了getBody()方法，                    //所以我们只要重写ReactorServerHttpRequest的getbody方法，加上我们读取的逻辑就行了，                    //gateway给我们提供了装饰类ServerHttpRequestDecorator,我们只需把过滤器的优先级设置高于NettyRoutingFilter(实际他已经是倒数第二的优先级了)，且把ReactorServerHttpRequest替换成ServerHttpRequestDecorator就行了                    .send(request.getBody().map(dataBuffer ->                            ((NettyDataBuffer) dataBuffer).getNativeBuffer()));        });给个stackoverflow的伪代码ServerHttpRequestDecorator decoratedRequest = new ServerHttpRequestDecorator(request) {             @Override            public Flux
      
        getBody() {                  StringBuilder sb=new StringBuilder();                  return  super.getBody().map(dataBuffer -> {                    // probably should reuse buffers                     byte[] content = new byte[dataBuffer.readableByteCount()];                    dataBuffer.read(content);                    byte[] uppedContent = new String(content, Charset.forName("UTF-8")).toUpperCase().getBytes();                    return bufferFactory.wrap(uppedContent);                }) ;             }};            //再说说记录返回的json,在NettyRoutingFilter类的154行，请求第三方服务反回后，            // Defer committing the response until all route filters have run            // Put client response as ServerWebExchange attribute and write response later NettyWriteResponseFilter            //注释说了把返回结果放进ServerWebExchange 的参数里了，并且在NettyWriteResponseFilter读取            exchange.getAttributes().put(CLIENT_RESPONSE_ATTR, res);看NettyWriteResponseFilter的读取代码，public Mono
       
         filter(ServerWebExchange exchange, GatewayFilterChain chain) {       return chain.filter(exchange).then(Mono.defer(() -> {           //拿出NettyRoutingFilter放进去的Response             HttpClientResponse clientResponse = exchange.getAttribute(CLIENT_RESPONSE_ATTR);            if (clientResponse == null) {//空的就不过直接到下一个过滤器                return Mono.empty();            }            log.trace("NettyWriteResponseFilter start");            ServerHttpResponse response = exchange.getResponse();            NettyDataBufferFactory factory = (NettyDataBufferFactory) response.bufferFactory();            //TODO: what if it's not netty            final Flux
        
          body = clientResponse.receive()                    .retain() //TODO: needed?                    .map(factory::wrap);            MediaType contentType = null;            try {                contentType = response.getHeaders().getContentType();            } catch (Exception e) {                log.trace("invalid media type", e);            }            //判断contentType是不是text/event-stream或者application/stream+json            //反正上面两种类型的结果我们肯定不用记录，所以我们重写response的writeWith方法就好，            //跟上面一样gateway也提供了个装饰器类ServerHttpResponseDecorator            return (isStreamingMediaType(contentType) ?                    response.writeAndFlushWith(body.map(Flux::just)) : response.writeWith(body));        }));    }上stackoverflow的伪代码DataBufferFactory bufferFactory = originalResponse.bufferFactory();      ServerHttpResponseDecorator decoratedResponse = new ServerHttpResponseDecorator(originalResponse) {        @Override        public Mono
         
           writeWith(Publisher
           body) { if (body instanceof Flux) { Flux
           fluxBody = (Flux
          ) body; return super.writeWith(fluxBody.map(dataBuffer -> { // probably should reuse buffers byte[] content = new byte[dataBuffer.readableByteCount()]; dataBuffer.read(content); byte[] uppedContent = new String(content, Charset.forName("UTF-8")).toUpperCase().getBytes(); return bufferFactory.wrap(uppedContent); })); } return super.writeWith(body); // if body is not a flux. never got there. } };
         
        
       
      
     
    

参考：

该如果返回的数据长度很长的话，数据可能会读不完全，如果出现读取时截取了中文字符，导致长度变多1位，进而json的右括号消失，也可参考下面链接