Spring Cloud Gateway中Filter获取Request Body的几种方式

最近团队中一位小伙伴写了个Spring Cloud Gateway Filter获取request body的方法，会偶尔出现报文不全的问题，数次都未解决

其实这个问题很多人碰到过，之前逛园子的时候恰巧看到位园友有发表过这方面内容，觉着甚好，故抄录一下。

原文地址：https://www.cnblogs.com/hyf-huangyongfei/p/12849406.html#4916467   

Spring Cloud Gateway Filter获取request body的方法有四种实现

1、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

2、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

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）。

3、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。

4、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

参考资料：https://www.codercto.com/a/52970.html