Spring Cloud Gateway 获取请求体（Request Body）的多种方法

一、直接在全局拦截器中获取，伪代码如下

private String resolveBodyFromRequest(ServerHttpRequest serverHttpRequest){

  Flux<DataBuffer> body = serverHttpRequest.getBody();

  AtomicReference<String> bodyRef = new AtomicReference<>();

  body.subscribe(buffer -> {

   CharBuffer charBuffer = StandardCharsets.UTF_8.decode(buffer.asByteBuffer());

   DataBufferUtils.release(buffer);

   bodyRef.set(charBuffer.toString());

  });

  return bodyRef.get();

 }

存在的缺陷：其他拦截器无法再通过该方式获取请求体（因为请求体已被消费），并且会抛出异常

Only one connection receive subscriber allowed.Caused by: java.lang.IllegalStateException: Only one connection receive subscriber allowed.

异常原因：实际上spring-cloud-gateway反向代理的原理是，首先读取原请求的数据，然后构造一个新的请求，将原请求的数据封装到新的请求中，然后再转发出去。然而我们在他封装之前读取了一次request body，而request body只能读取一次。因此就出现了上面的错误。

再者受版本限制

这种方法在spring-boot-starter-parent 2.0.6.RELEASE + Spring Cloud Finchley.SR2 body 中生效，

但是在spring-boot-starter-parent 2.1.0.RELEASE + Spring Cloud Greenwich.M3 body 中不生效，总是为空

二、先在全局过滤器中获取，然后再把request重新包装，继续向下传递传递

@Override
 public GatewayFilter apply(NameValueConfig nameValueConfig) {
  return (exchange, chain) -> {
   URI uri = exchange.getRequest().getURI();
   URI ex = UriComponentsBuilder.fromUri(uri).build(true).toUri();
   ServerHttpRequest request = exchange.getRequest().mutate().uri(ex).build();
   if("POST".equalsIgnoreCase(request.getMethodValue())){//判断是否为POST请求
    Flux<DataBuffer> body = request.getBody();
    AtomicReference<String> bodyRef = new AtomicReference<>();
    body.subscribe(dataBuffer -> {
     CharBuffer charBuffer = StandardCharsets.UTF_8.decode(dataBuffer.asByteBuffer());
     DataBufferUtils.release(dataBuffer);
     bodyRef.set(charBuffer.toString());
    });//读取request body到缓存
    String bodyStr = bodyRef.get();//获取request body
    System.out.println(bodyStr);//这里是我们需要做的操作
    DataBuffer bodyDataBuffer = stringBuffer(bodyStr);
    Flux<DataBuffer> bodyFlux = Flux.just(bodyDataBuffer);

    request = new ServerHttpRequestDecorator(request){
     @Override
     public Flux<DataBuffer> getBody() {
      return bodyFlux;
     }
    };//封装我们的request
   }
   return chain.filter(exchange.mutate().request(request).build());
  };
 }
　protected DataBuffer stringBuffer(String value) {
  byte[] bytes = value.getBytes(StandardCharsets.UTF_8);

  NettyDataBufferFactory nettyDataBufferFactory = new NettyDataBufferFactory(ByteBufAllocator.DEFAULT);
  DataBuffer buffer = nettyDataBufferFactory.allocateBuffer(bytes.length);
  buffer.write(bytes);
  return buffer;
 }

该方案的缺陷：request body获取不完整（因为异步原因），只能获取1024B的数据。并且请求体超过1024B，会出现响应超慢（因为我是开启了熔断）。

三、过滤器加路线定位器

翻查源码发现ReadBodyPredicateFactory里面缓存了request body的信息，于是在自定义router中配置了ReadBodyPredicateFactory，然后在filter中通过cachedRequestBodyObject缓存字段获取request body信息。

/**
 * @description: 获取POST请求的请求体
 * ReadBodyPredicateFactory 发现里面缓存了request body的信息，
 * 于是在自定义router中配置了ReadBodyPredicateFactory
 * @modified:
 */
@EnableAutoConfiguration
@Configuration
public class RouteLocatorRequestBoby{
　　 //自定义过滤器
 @Resource
 private ReqTraceFilter reqTraceFilter;
　　
 @Resource
 private RibbonLoadBalancerClient ribbonLoadBalancerClient;

 private static final String SERVICE = "/leap/**";

 private static final String HTTP_PREFIX = "http://";

 private static final String COLON = ":";

 @Bean
 public RouteLocator myRoutes(RouteLocatorBuilder builder) {
  //通过负载均衡获取服务实例
  ServiceInstance instance = ribbonLoadBalancerClient.choose("PLATFORM-SERVICE");
  //拼接路径
  StringBuilder forwardAddress = new StringBuilder(HTTP_PREFIX);
  forwardAddress.append(instance.getHost())
    .append(COLON)
    .append(instance.getPort());
  return builder.routes()
    //拦截请求类型为POST Content-Type application/json application/json;charset=UTF-8
    .route(r -> r
        .header(HttpHeaders.CONTENT_TYPE,
          MediaType.APPLICATION_JSON_VALUE + MediaType.APPLICATION_JSON_UTF8_VALUE)
        .and()
        .method(HttpMethod.POST)
        .and()
        //获取缓存中的请求体
        .readBody(Object.class, readBody -> {
         return true;
        })
        .and()
        .path(SERVICE)
        //把请求体传递给拦截器reqTraceFilter
        .filters(f -> {
         f.filter(reqTraceFilter);
         return f;
        })
        .uri(forwardAddress.toString())).build();
 }

/**
 * @description: 过滤器，用于获取请求体，和处理请求体业务，列如记录日志
 * @modified:
 */
@Component
public class ReqTraceFilter implements GlobalFilter, GatewayFilter,Ordered {

 private static final String CONTENT_TYPE = "Content-Type";

 private static final String CONTENT_TYPE_JSON = "application/json";
　　
 //获取请求路由详细信息Route route = exchange.getAttribute(GATEWAY_ROUTE_BEAN)
 private static final String GATEWAY_ROUTE_BEAN = "org.springframework.cloud.gateway.support.ServerWebExchangeUtils.gatewayRoute";

 private static final String CACHE_REQUEST_BODY_OBJECT_KEY = "cachedRequestBodyObject";
 @Override
 public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
  ServerHttpRequest request = exchange.getRequest();
  //判断过滤器是否执行
  String requestUrl = RequestUtils.getCurrentRequest(request);
  if (!RequestUtils.isFilter(requestUrl)) {
   String bodyStr = "";
   String contentType = request.getHeaders().getFirst(CONTENT_TYPE);
   String method = request.getMethodValue();
   //判断是否为POST请求
   if (null != contentType && HttpMethod.POST.name().equalsIgnoreCase(method) && contentType.contains(CONTENT_TYPE_JSON)) {
    Object cachedBody = exchange.getAttribute(CACHE_REQUEST_BODY_OBJECT_KEY);
    if(null != cachedBody){
     bodyStr = cachedBody.toString();
    }
   }
   if (HttpMethod.GET.name().equalsIgnoreCase(method)) {
    bodyStr = request.getQueryParams().toString();
   }

   log.info("请求体内容：{}",bodyStr);
  }
  return chain.filter(exchange);
 }

 @Override
 public int getOrder() {
  return 5;
 }
}

该方案优点：这种解决，一不会带来重复读取问题，二不会带来requestbody取不全问题。三在低版本的Spring Cloud Finchley.SR2也可以运行。

缺点：不支持multipart/form-data（异常415），这个致命。

四、通过org.springframework.cloud.gateway.filter.factory.rewrite包下有个ModifyRequestBodyGatewayFilterFactory，顾名思义，这就是修改 Request Body 的过滤器工厂类。

@Component
@Slf4j
public class ReqTraceFilter implements GlobalFilter, GatewayFilter, Ordered {

 @Resource
 private IPlatformFeignClient platformFeignClient;

 /**
  * httpheader，traceId的key名称
  */
 private static final String REQUESTID = "traceId";

 private static final String CONTENT_TYPE = "Content-Type";

 private static final String CONTENT_TYPE_JSON = "application/json";

 private static final String GATEWAY_ROUTE_BEAN = "org.springframework.cloud.gateway.support.ServerWebExchangeUtils.gatewayRoute";

 @Override
 public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
  ServerHttpRequest request = exchange.getRequest();
  //判断过滤器是否执行
  String requestUrl = RequestUtils.getCurrentRequest(request);
  if (!RequestUtils.isFilter(requestUrl)) {
   String bodyStr = "";
   String contentType = request.getHeaders().getFirst(CONTENT_TYPE);
   String method = request.getMethodValue();
   //判断是否为POST请求
   if (null != contentType && HttpMethod.POST.name().equalsIgnoreCase(method) && contentType.contains(CONTENT_TYPE_JSON)) {
    ServerRequest serverRequest = new DefaultServerRequest(exchange);
    List<String> list = new ArrayList<>();
    // 读取请求体
    Mono<String> modifiedBody = serverRequest.bodyToMono(String.class)
      .flatMap(body -> {
       //记录请求体日志
       final String nId = saveRequestOperLog(exchange, body);
       //记录日志id
       list.add(nId);
       return Mono.just(body);
      });

    BodyInserter bodyInserter = BodyInserters.fromPublisher(modifiedBody, String.class);
    HttpHeaders headers = new HttpHeaders();
    headers.putAll(exchange.getRequest().getHeaders());
    headers.remove(HttpHeaders.CONTENT_LENGTH);

    CachedBodyOutputMessage outputMessage = new CachedBodyOutputMessage(exchange, headers);
    return bodyInserter.insert(outputMessage, new BodyInserterContext())
      .then(Mono.defer(() -> {
       ServerHttpRequestDecorator decorator = new ServerHttpRequestDecorator(
         exchange.getRequest()) {
        @Override
        public HttpHeaders getHeaders() {
         long contentLength = headers.getContentLength();
         HttpHeaders httpHeaders = new HttpHeaders();
         httpHeaders.putAll(super.getHeaders());
         httpHeaders.put(REQUESTID,list);
         if (contentLength > 0) {
          httpHeaders.setContentLength(contentLength);
         } else {
          httpHeaders.set(HttpHeaders.TRANSFER_ENCODING, "chunked");
         }
         return httpHeaders;
        }

        @Override
        public Flux<DataBuffer> getBody() {
         return outputMessage.getBody();
        }
       };

       return chain.filter(exchange.mutate().request(decorator).build());
      }));
   }
   if (HttpMethod.GET.name().equalsIgnoreCase(method)) {
    bodyStr = request.getQueryParams().toString();
    String nId = saveRequestOperLog(exchange, bodyStr);
    ServerHttpRequest userInfo = exchange.getRequest().mutate()
      .header(REQUESTID, nId).build();
    return chain.filter(exchange.mutate().request(userInfo).build());
   }

  }
  return chain.filter(exchange);
 }

 /**
  * 保存请求日志
  *
  * @param exchange
  * @param requestParameters
  * @return
  */
 private String saveRequestOperLog(ServerWebExchange exchange, String requestParameters) {
  log.debug("接口请求参数：{}", requestParameters);
  ServerHttpRequest request = exchange.getRequest();
  String ip = Objects.requireNonNull(request.getRemoteAddress()).getAddress().getHostAddress();
  SaveOperLogVO vo = new SaveOperLogVO();
  vo.setIp(ip);
  vo.setReqUrl(RequestUtils.getCurrentRequest(request));
  vo.setReqMethod(request.getMethodValue());
  vo.setRequestParameters(requestParameters);

  Route route = exchange.getAttribute(GATEWAY_ROUTE_BEAN);
  //是否配置路由
  if (route != null) {
   vo.setSubsystem(route.getId());
  }
  ResEntity<String> res = platformFeignClient.saveOperLog(vo);
  log.debug("当前请求ID返回的数据：{}", res);
  return res.getData();
 }

 @Override
 public int getOrder() {
  return 5;
 }
}

该方案：完美解决以上所有问题

参考文档：https://www.codercto.com/a/52970.html

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