获取SpringCloud gateway响应的response的值，记录踩坑

最近在做网关改造，想要通过Gateway过滤器获取ResponseBody的值，查看了网上的帖子和官网内容：

帖子：https://cloud.tencent.com/developer/article/1384111

官网：https://github.com/spring-cloud/spring-cloud-gateway/blob/master/spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/filter/factory/rewrite/ModifyResponseBodyGatewayFilterFactory.java

但在实际操作中却掉坑里了，居然不起作用，就是不进重写但writeWith方法

@Component
@Order(-2)
public class EncryptResponseBodyFilter implements GlobalFilter {

    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        ServerHttpResponse originalResponse = exchange.getResponse();
        DataBufferFactory bufferFactory = originalResponse.bufferFactory();
        ServerHttpResponseDecorator response = new ServerHttpResponseDecorator(originalResponse) {

            @Override
            public Mono<Void> writeWith(Publisher<? extends DataBuffer> body) {
                if (getStatusCode().equals(HttpStatus.OK) && body instanceof Flux) {

                    Flux<? extends DataBuffer> fluxBody = Flux.from(body);
                    return super.writeWith(fluxBody.map(dataBuffer -> {
                        // probably should reuse buffers
                        byte[] content = new byte[dataBuffer.readableByteCount()];
                        dataBuffer.read(content);
                        //释放掉内存
                        DataBufferUtils.release(dataBuffer);
                        String s = new String(content, Charset.forName("UTF-8"));
                        //TODO，s就是response的值，想修改、查看就随意而为了
                        byte[] uppedContent = s.getBytes();
                        return bufferFactory.wrap(uppedContent);
                    }));
                }
                return super.writeWith(body);
            }

            @Override
            public Mono<Void> writeAndFlushWith(Publisher<? extends Publisher<? extends DataBuffer>> body) {
                return writeWith(Flux.from(body)
                        .flatMapSequential(p -> p));
            }
        };37         return chain.filter(exchange.mutate().response(response).build());
    }

后来与帖子和官网代码内容对比，只有Order的方式不同，就换了下实现Ordered重写getOrder方法方式试试，结果出乎意料，居然好用了！！！

真的是绞尽脑汁啊，浪费了不少时间。。。。

后来发现响应数据存在分段响应的问题：

参考：https://blog.csdn.net/fayeyiwang/article/details/9137// JSON响应数据拼接容器

private static Joiner joiner = Joiner.on("");

@Override
public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
    ServerHttpResponse originalResponse = exchange.getResponse();
    DataBufferFactory bufferFactory = originalResponse.bufferFactory();
    ServerHttpResponseDecorator response = new ServerHttpResponseDecorator(originalResponse) {
        @Override
        public Mono<Void> writeWith(Publisher<? extends DataBuffer> body) {
            if (getStatusCode().equals(HttpStatus.OK) && body instanceof Flux) {
                // 获取ContentType，判断是否返回JSON格式数据
                String originalResponseContentType = exchange.getAttribute(ORIGINAL_RESPONSE_CONTENT_TYPE_ATTR);
                if(StringUtils.isNotBlank(originalResponseContentType) && originalResponseContentType.contains("application/json")) {
                   Flux<? extends DataBuffer> fluxBody = Flux.from(body);
                   return super.writeWith(fluxBody.buffer().map(dataBuffers -> {//解决返回体分段传输
                      List<String> list = Lists.newArrayList();
                      dataBuffers.forEach(dataBuffer -> {
                         try {
                            byte[] content = new byte[dataBuffer.readableByteCount()];
                            dataBuffer.read(content);
                            DataBufferUtils.release(dataBuffer);

                            list.add(new String(content, "utf-8"));
                         } catch (Exception e) {
                            logger.info("动态加载API加密规则失败，失败原因：{}", Throwables.getStackTraceAsString(e));
                         }
                       });
                       String responseData = joiner.join(list);
                       // 二次处理（加密/过滤等）如果不需要做二次处理可直接跳过下行
                       responseData = beforeBodyWriteInternal(responseData, exchange.getRequest());
                       byte[] uppedContent = new String(responseData.getBytes(), Charset.forName("UTF-8")).getBytes();
                       originalResponse.getHeaders().setContentLength(uppedContent.length);
                       return bufferFactory.wrap(uppedContent);
                    }));
                 }
            }
            return super.writeWith(body);
        }

        @Override
        public Mono<Void> writeAndFlushWith(Publisher<? extends Publisher<? extends DataBuffer>> body) {
            return writeWith(Flux.from(body).flatMapSequential(p -> p));
        }
    };
    return chain.filter(exchange.mutate().response(response).build());
}