springcloud 基础组件-Feign 调用流程

原图来自：https://blog.csdn.net/luanlouis/article/details/82821294

所有注册的feign client

org.springframework.cloud.openfeign.FeignAutoConfiguration#feignContext

决定使用哪种client的地方

org.springframework.cloud.openfeign.FeignAutoConfiguration.OkHttpFeignConfiguration#feignClient
org.springframework.cloud.openfeign.FeignAutoConfiguration.HttpClientFeignConfiguration#feignClient
feign.Client.Default#Default

feign 所有拦截器

feign.SynchronousMethodHandler#targetRequest

  Request targetRequest(RequestTemplate template) {
    for (RequestInterceptor interceptor : requestInterceptors) {
      interceptor.apply(template);
    }
    return target.apply(template);
  }

feign feign 发送请求的地方（接口）

feign.Client#execute

默认的jdk 发送请求的地方

feign.Client.Default#execute

httpclient 发送请求的地方

org.apache.http.protocol.HttpRequestExecutor#doSendRequest

httpclient request 拦截器

org.apache.http.protocol.HttpRequestExecutor#preProcess
org.apache.http.protocol.ImmutableHttpProcessor#process(org.apache.http.HttpRequest, org.apache.http.protocol.HttpContext)

    @Override
    public void process(
            final HttpResponse response,
            final HttpContext context) throws IOException, HttpException {
        for (final HttpResponseInterceptor responseInterceptor : this.responseInterceptors) {
            responseInterceptor.process(response, context);
        }
    }

httpclient response 拦截器

org.apache.http.protocol.HttpRequestExecutor#postProcess
org.apache.http.protocol.ImmutableHttpProcessor#process(org.apache.http.HttpResponse, org.apache.http.protocol.HttpContext)

    @Override
    public void process(
            final HttpResponse response,
            final HttpContext context) throws IOException, HttpException {
        for (final HttpResponseInterceptor responseInterceptor : this.responseInterceptors) {
            responseInterceptor.process(response, context);
        }
    }

okhttp 发送请求的地方

okhttp3.internal.http.CallServerInterceptor#intercept

okhttp 拦截器

okhttp3.RealCall#getResponseWithInterceptorChain

  Response getResponseWithInterceptorChain() throws IOException {
    // Build a full stack of interceptors.
    List<Interceptor> interceptors = new ArrayList<>();
    interceptors.addAll(client.interceptors());
    interceptors.add(retryAndFollowUpInterceptor);
    interceptors.add(new BridgeInterceptor(client.cookieJar()));
    interceptors.add(new CacheInterceptor(client.internalCache()));
    interceptors.add(new ConnectInterceptor(client));
    if (!forWebSocket) {
      interceptors.addAll(client.networkInterceptors());
    }
    interceptors.add(new CallServerInterceptor(forWebSocket));

    Interceptor.Chain chain = new RealInterceptorChain(
        interceptors, null, null, null, 0, originalRequest);
    return chain.proceed(originalRequest);
  }