【Spring Cloud GateWay】ServerHttpResponseDecorator不生效

悠悠 2024-03-30 16:47 63阅读 0赞

#### 文章目录 ####

*  1. BUG描述
 *  2. BUG解决
 *  3. BUG分析

## 1. BUG描述 ##

在Spring Cloud Gateway使用编码的方式实现一个全局拦截器，在全局拦截器中想要打印响应日志。

于是自己装饰了一个具有打印日志功能的`ServerHttpResponseDecorator`，但是在转发后的服务返回响应的时候，`ServerHttpResponseDecorator`的`writeWith`却并没有执行。

@Component
    @Slf4j
    public class CustomGlobaFilter implements GlobalFilter, Ordered {
        
    
        @Override
        public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        
            //响应日志
            return handleResponse(exchange, chain);
        }
    
        public Mono<Void> handleResponse(ServerWebExchange exchange, GatewayFilterChain chain) {
        
            try {
        
                ServerHttpResponse originalResponse = exchange.getResponse();
                // 缓存数据的工厂
                DataBufferFactory bufferFactory = originalResponse.bufferFactory();
                // 拿到响应码
                HttpStatus statusCode = originalResponse.getStatusCode();
                if (statusCode == HttpStatus.OK) {
        
                    // 装饰，增强能力
                    ServerHttpResponseDecorator decoratedResponse = new ServerHttpResponseDecorator(originalResponse) {
        
                        // 等调用完转发的接口后才会执行
                        @Override
                        public Mono<Void>  writeWith(Publisher<? extends DataBuffer> body) {
        
                            log.info("body instanceof Flux: {}", (body instanceof Flux));
                            if (body instanceof Flux) {
        
                                Flux<? extends DataBuffer> fluxBody = Flux.from(body);
                                // 往返回值里写数据
                                // 拼接字符串
                                return super.writeWith(
                                        fluxBody.map(dataBuffer -> {
        
                                            byte[] content = new byte[dataBuffer.readableByteCount()];
                                            dataBuffer.read(content);
                                            //释放掉内存
                                            DataBufferUtils.release(dataBuffer);
                                            // 构建日志
                                            StringBuilder sb2 = new StringBuilder(200);
                                            List<Object> rspArgs = new ArrayList<>();
                                            rspArgs.add(originalResponse.getStatusCode());
                                            //data
                                            String data = new String(content, StandardCharsets.UTF_8); 
                                            sb2.append(data);
                                            // 打印日志
                                            log.info("响应结果：" + data);
                                            return bufferFactory.wrap(content);
                                        }));
                            } else {
        
                                // 8. 调用失败，返回一个规范的错误码
                                log.error("<--- {} 响应code异常", getStatusCode());
                            }
                            return super.writeWith(body);
                        }
                    };
                    // 设置 response 对象为装饰过的
                    return chain.filter(exchange.mutate().response(decoratedResponse).build());
                }
                // 降级处理返回数据
                return chain.filter(exchange); 
            } catch (Exception e) {
        
                log.error("网关处理响应异常" + e);
                return chain.filter(exchange);
            }
        }
    
        @Override
        public int getOrder() {
        
            return 0;
        }
    }

--------------------

## 2. BUG解决 ##

将`getOrder`方法的返回值设置为`-2`

@Override
    public int getOrder() {
        
        return -2;
    }

修改成之后，`writeWith`方法在服务返回响应的时候就能被调用了。

--------------------

## 3. BUG分析 ##

在SpringCloudGateway中，有很多默认的全局过滤器。

![img][]

它们对应的order值如下图所示

![img][img 1]

因为我这里的`CustomGlobaFilter`实现了`Ordered`，所以它的order就是它自己设定的值。

否则，它就没有order。

查看了大量信息，最后得知，`自定义的GlobaFilter的order必须小于-1`，否则标准 `NettyWriteResponseFilter`将在过滤器有机会被调用之前发送响应。

--------------------

> 参考：
> 
> 1.  [Allow modification of the response body · Issue \#47 · spring-cloud/spring-cloud-gateway (github.com)][Allow modification of the response body _ Issue _47 _ spring-cloud_spring-cloud-gateway _github.com]
> 2.  [获取SpringCloud gateway 响应的response的值，可以查看、修改 - 腾讯云开发者社区-腾讯云 (tencent.com)][SpringCloud gateway _response_ - _-_ _tencent.com]
> 3.  [gateway的ServerHttpResponseDecorator后不起作用?-有问必答-CSDN问答][gateway_ServerHttpResponseDecorator_-_-CSDN]

[img]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/30/59dc9886cbb74b82ab84a080f406a9b2.png
[img 1]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/30/011b74f95c0748919f1d601b3803a547.png
[Allow modification of the response body _ Issue _47 _ spring-cloud_spring-cloud-gateway _github.com]: https://github.com/spring-cloud/spring-cloud-gateway/issues/47
[SpringCloud gateway _response_ - _-_ _tencent.com]: https://cloud.tencent.com/developer/article/1384111
[gateway_ServerHttpResponseDecorator_-_-CSDN]: https://ask.csdn.net/questions/7429978