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

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