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本文轉載自微信公眾號「JAVA日知錄」，作者單一色調。轉載本文請聯系JAVA日知錄公眾號。 

請求響應日志是日常開發調試定位問題的重要手段，在微服務中引入SpringCloud Gateway后我們希望在網關層統一進行日志的收集。

本節內容將實現以下兩個功能：

獲取請求的輸入輸出參數，封裝成自定義日志

將日志發送到MongoDB進行存儲

獲取輸入輸出參數

首先我們先定義一個日志體

@Data 
public class GatewayLog { 
    /**訪問實例*/ 
    private String targetServer; 
    /**請求路徑*/ 
    private String requestPath; 
    /**請求方法*/ 
    private String requestMethod; 
    /**協議 */ 
    private String schema; 
    /**請求體*/ 
    private String requestBody; 
    /**響應體*/ 
    private String responseData; 
    /**請求ip*/ 
    private String ip; 
 /**請求時間*/ 
    private Date requestTime; 
 /**響應時間*/ 
    private Date responseTime; 
    /**執行時間*/ 
    private long executeTime; 
} 

【關鍵】在網關定義日志過濾器，獲取輸入輸出參數

/** 
 * 日志過濾器，用于記錄日志 
 * @author jianzh5 
 * @date 2020/3/24 17:17 
 */ 
@Slf4j 
@Component 
public class AccessLogFilter implements GlobalFilter, Ordered { 
    @Autowired 
    private AccessLogService accessLogService; 
 
    private final List<HttpMessageReader<?>> messageReaders = HandlerStrategies.withDefaults().messageReaders(); 
 
    @Override 
    public int getOrder() { 
        return -100; 
    } 
 
    @Override 
    @SuppressWarnings("unchecked") 
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) { 
 
        ServerHttpRequest request = exchange.getRequest(); 
 
        // 請求路徑 
        String requestPath = request.getPath().pathWithinApplication().value(); 
 
        Route route = getGatewayRoute(exchange); 
 
 
        String ipAddress = WebUtils.getServerHttpRequestIpAddress(request); 
 
        GatewayLog gatewayLog = new GatewayLog(); 
        gatewayLog.setSchema(request.getURI().getScheme()); 
        gatewayLog.setRequestMethod(request.getMethodValue()); 
        gatewayLog.setRequestPath(requestPath); 
        gatewayLog.setTargetServer(route.getId()); 
        gatewayLog.setRequestTime(new Date()); 
        gatewayLog.setIp(ipAddress); 
 
        MediaType mediaType = request.getHeaders().getContentType(); 
 
        if(MediaType.APPLICATION_FORM_URLENCODED.isCompatibleWith(mediaType) || MediaType.APPLICATION_JSON.isCompatibleWith(mediaType)){ 
            return writeBodyLog(exchange, chain, gatewayLog); 
        }else{ 
            return writeBasicLog(exchange, chain, gatewayLog); 
        } 
    } 
 
    private Mono<Void> writeBasicLog(ServerWebExchange exchange, GatewayFilterChain chain, GatewayLog accessLog) { 
        StringBuilder builder = new StringBuilder(); 
        MultiValueMap<String, String> queryParams = exchange.getRequest().getQueryParams(); 
        for (Map.Entry<String, List<String>> entry : queryParams.entrySet()) { 
            builder.append(entry.getKey()).append("=").append(StringUtils.join(entry.getValue(), ",")); 
        } 
        accessLog.setRequestBody(builder.toString()); 
 
        //獲取響應體 
        ServerHttpResponseDecorator decoratedResponse = recordResponseLog(exchange, accessLog); 
 
        return chain.filter(exchange.mutate().response(decoratedResponse).build()) 
                .then(Mono.fromRunnable(() -> { 
                    // 打印日志 
                    writeAccessLog(accessLog); 
                })); 
    } 
 
 
    /** 
     * 解決 request body 只能讀取一次問題， 
     * 參考: org.springframework.cloud.gateway.filter.factory.rewrite.ModifyRequestBodyGatewayFilterFactory 
     * @param exchange 
     * @param chain 
     * @param gatewayLog 
     * @return 
     */ 
    @SuppressWarnings("unchecked") 
    private Mono writeBodyLog(ServerWebExchange exchange, GatewayFilterChain chain, GatewayLog gatewayLog) { 
        ServerRequest serverRequest = ServerRequest.create(exchange,messageReaders); 
 
        Mono<String> modifiedBody = serverRequest.bodyToMono(String.class) 
                .flatMap(body ->{ 
                    gatewayLog.setRequestBody(body); 
                    return Mono.just(body); 
                }); 
 
        // 通過 BodyInserter 插入 body(支持修改body), 避免 request body 只能獲取一次 
        BodyInserter bodyInserter = BodyInserters.fromPublisher(modifiedBody, String.class); 
        HttpHeaders headers = new HttpHeaders(); 
        headers.putAll(exchange.getRequest().getHeaders()); 
        // the new content type will be computed by bodyInserter 
        // and then set in the request decorator 
        headers.remove(HttpHeaders.CONTENT_LENGTH); 
 
        CachedBodyOutputMessage outputMessage = new CachedBodyOutputMessage(exchange, headers); 
 
        return bodyInserter.insert(outputMessage,new BodyInserterContext()) 
                .then(Mono.defer(() -> { 
                    // 重新封裝請求 
                    ServerHttpRequest decoratedRequest = requestDecorate(exchange, headers, outputMessage); 
 
                    // 記錄響應日志 
                    ServerHttpResponseDecorator decoratedResponse = recordResponseLog(exchange, gatewayLog); 
 
                    // 記錄普通的 
                    return chain.filter(exchange.mutate().request(decoratedRequest).response(decoratedResponse).build()) 
                            .then(Mono.fromRunnable(() -> { 
                                // 打印日志 
                                writeAccessLog(gatewayLog); 
                            })); 
                })); 
    } 
 
    /** 
     * 打印日志 
     * @author javadaily 
     * @date 2021/3/24 14:53 
     * @param gatewayLog 網關日志 
     */ 
    private void writeAccessLog(GatewayLog gatewayLog) { 
        log.info(gatewayLog.toString());   
    } 
 
 
 
    private Route getGatewayRoute(ServerWebExchange exchange) { 
        return exchange.getAttribute(ServerWebExchangeUtils.GATEWAY_ROUTE_ATTR); 
    } 
 
 
    /** 
     * 請求裝飾器，重新計算 headers 
     * @param exchange 
     * @param headers 
     * @param outputMessage 
     * @return 
     */ 
    private ServerHttpRequestDecorator requestDecorate(ServerWebExchange exchange, HttpHeaders headers, 
                                                       CachedBodyOutputMessage outputMessage) { 
        return new ServerHttpRequestDecorator(exchange.getRequest()) { 
            @Override 
            public HttpHeaders getHeaders() { 
                long contentLength = headers.getContentLength(); 
                HttpHeaders httpHeaders = new HttpHeaders(); 
                httpHeaders.putAll(super.getHeaders()); 
                if (contentLength > 0) { 
                    httpHeaders.setContentLength(contentLength); 
                } else { 
                    // TODO: this causes a 'HTTP/1.1 411 Length Required' // on 
                    // httpbin.org 
                    httpHeaders.set(HttpHeaders.TRANSFER_ENCODING, "chunked"); 
                } 
                return httpHeaders; 
            } 
 
            @Override 
            public Flux<DataBuffer> getBody() { 
                return outputMessage.getBody(); 
            } 
        }; 
    } 
 
 
    /** 
     * 記錄響應日志 
     * 通過 DataBufferFactory 解決響應體分段傳輸問題。 
     */ 
    private ServerHttpResponseDecorator recordResponseLog(ServerWebExchange exchange, GatewayLog gatewayLog) { 
        ServerHttpResponse response = exchange.getResponse(); 
        DataBufferFactory bufferFactory = response.bufferFactory(); 
 
        return new ServerHttpResponseDecorator(response) { 
            @Override 
            public Mono<Void> writeWith(Publisher<? extends DataBuffer> body) { 
                if (body instanceof Flux) { 
                    Date responseTime = new Date(); 
                    gatewayLog.setResponseTime(responseTime); 
                    // 計算執行時間 
                    long executeTime = (responseTime.getTime() - gatewayLog.getRequestTime().getTime()); 
 
                    gatewayLog.setExecuteTime(executeTime); 
 
                    // 獲取響應類型，如果是 json 就打印 
                    String originalResponseContentType = exchange.getAttribute(ServerWebExchangeUtils.ORIGINAL_RESPONSE_CONTENT_TYPE_ATTR); 
 
 
                    if (ObjectUtil.equal(this.getStatusCode(), HttpStatus.OK) 
                            && StringUtil.isNotBlank(originalResponseContentType) 
                            && originalResponseContentType.contains("application/json")) { 
 
                        Flux<? extends DataBuffer> fluxBody = Flux.from(body); 
                        return super.writeWith(fluxBody.buffer().map(dataBuffers -> { 
 
                            // 合并多個流集合，解決返回體分段傳輸 
                            DataBufferFactory dataBufferFactory = new DefaultDataBufferFactory(); 
                            DataBuffer join = dataBufferFactory.join(dataBuffers); 
                            byte[] content = new byte[join.readableByteCount()]; 
                            join.read(content); 
 
                            // 釋放掉內存 
                            DataBufferUtils.release(join); 
                            String responseResult = new String(content, StandardCharsets.UTF_8); 
 
 
 
                            gatewayLog.setResponseData(responseResult); 
 
                            return bufferFactory.wrap(content); 
                        })); 
                    } 
                } 
                // if body is not a flux. never got there. 
                return super.writeWith(body); 
            } 
        }; 
    } 
} 

代碼較長建議直接拷貝到編輯器，只要注意下面一個關鍵點：

getOrder()方法返回的值必須要<-1，「否則標準的NettyWriteResponseFilter將在您的過濾器被調用的機會之前發送響應，即不會執行獲取后端響應參數的方法」

通過上面的兩步我們已經可以獲取到請求的輸入輸出參數了，在 writeAccessLog()中將其輸出到了日志文件，大家可以在Postman發送請求觀察日志。

存儲日志

如果需要將日志持久化方便后期檢索的話可以考慮將日志存儲在MongoDB中，實現過程很簡單。(安裝MongoDB可以參考這篇文章：實戰|MongoDB的安裝配置)

• 引入MongoDB

<dependency> 
    <groupId>org.springframework.boot</groupId> 
    <artifactId>spring-boot-starter-data-mongodb-reactive</artifactId> 
</dependency> 

由于gateway是基于webflux，所以我們需要選擇reactive版本。

• 在GatewayLog上添加對應的注解

@Data 
@Document 
public class GatewayLog { 
    @Id 
    private String id; 
 ... 
} 

• 建立AccessLogRepository

@Repository 
public interface AccessLogRepository extends ReactiveMongoRepository<GatewayLog,String> { 
   
} 

• 建立Service

public interface AccessLogService { 
 
    /** 
     * 保存AccessLog 
     * @param gatewayLog 請求響應日志 
     * @return 響應日志 
     */ 
    Mono<GatewayLog> saveAccessLog(GatewayLog gatewayLog); 
 
} 

• 建立實現類

@Service 
public class AccessLogServiceImpl implements AccessLogService { 
    @Autowired 
    private AccessLogRepository accessLogRepository; 
 
    @Override 
    public Mono<GatewayLog> saveAccessLog(GatewayLog gatewayLog) { 
        return accessLogRepository.insert(gatewayLog); 
    } 
} 

• 在Nacos配置中心添加MongoDB對應配置

spring: 
  data: 
    mongodb: 
      host: xxx.xx.x.xx 
      port: 27017 
      database: accesslog 
      username: accesslog 
      password: xxxxxx 

執行請求，打開MongoDB客戶端，查看日志結果

以上，希望對你有所幫助!