OkHttp源碼解讀總結(七)--->RetryAndFollowUpInterceptor攔截器

OkHttp源碼解讀總結(七)—>RetryAndFollowUpInterceptor攔截器

標籤（空格分隔）： OkHttp源碼 學習筆記

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前言

• 以下的相關知識總結是通過慕課網的相關學習和自己的相關看法,如果有需要的可以去查看一下慕課網的相關教學,感覺還可以。

主要作用

//官網介紹
This interceptor recovers from failures and follows redirects as necessary. It may throw an
 * {@link IOException} if the call was canceled.

主要負責失敗重連,並不是所有的網絡請求都會去失敗重連的,它是有一個範圍的,在okhttp內部進行檢測網絡請求的異常和響應碼的判斷,如果都在限制範圍內,那麼就可以進行失敗重連。

intercept()方法源碼

@Override public Response intercept(Chain chain) throws IOException {
    //獲取request對象
    Request request = chain.request();
    RealInterceptorChain realChain = (RealInterceptorChain) chain;
    //獲取當前請求的call對象
    Call call = realChain.call();
    //監聽器
    EventListener eventListener = realChain.eventListener();
    //創建一個StreamAllocation對象  用來建立http請求的網絡組件   用於獲取服務端的conn和數據傳輸的輸入輸出流  在這裏並沒有用到
    //// 三個參數分別對應，全局的連接池僅對http／2有用，連接線路Address, 堆棧對象
    streamAllocation = new StreamAllocation(client.connectionPool(), createAddress(request.url()),
        call, eventListener, callStackTrace);

    int followUpCount = 0;
    Response priorResponse = null;
    while (true) {
      if (canceled) {
        streamAllocation.release();
        throw new IOException("Canceled");
      }

      Response response;
      boolean releaseConnection = true;
      try {
        //執行下一個攔截器 即BridgeInterceptor
        response = realChain.proceed(request, streamAllocation, null, null);
        releaseConnection = false;
      } catch (RouteException e) {
        // The attempt to connect via a route failed. The request will not have been sent.
        //如果有異常 判斷是否需要恢復
        if (!recover(e.getLastConnectException(), false, request)) {
          throw e.getLastConnectException();
        }
        releaseConnection = false;
        continue;
      } catch (IOException e) {
        // An attempt to communicate with a server failed. The request may have been sent.
        boolean requestSendStarted = !(e instanceof ConnectionShutdownException);
        if (!recover(e, requestSendStarted, request)) throw e;
        releaseConnection = false;
        continue;
      } finally {
        // We're throwing an unchecked exception. Release any resources.
        if (releaseConnection) {
          streamAllocation.streamFailed(null);
          streamAllocation.release();
        }
      }

      // Attach the prior response if it exists. Such responses never have a body.
      if (priorResponse != null) {
        response = response.newBuilder()
            .priorResponse(priorResponse.newBuilder()
                    .body(null)
                    .build())
            .build();
      }

      Request followUp = followUpRequest(response);

      if (followUp == null) {
        if (!forWebSocket) {
          streamAllocation.release();
        }
        return response;
      }

      closeQuietly(response.body());
      //對重試的次數進行判斷  MAX_FOLLOW_UPS = 20 次
      if (++followUpCount > MAX_FOLLOW_UPS) {
        //釋放這個對象  
        streamAllocation.release();
        throw new ProtocolException("Too many follow-up requests: " + followUpCount);
      }

      if (followUp.body() instanceof UnrepeatableRequestBody) {
        streamAllocation.release();
        throw new HttpRetryException("Cannot retry streamed HTTP body", response.code());
      }

      if (!sameConnection(response, followUp.url())) {
        streamAllocation.release();
        streamAllocation = new StreamAllocation(client.connectionPool(),
            createAddress(followUp.url()), call, eventListener, callStackTrace);
      } else if (streamAllocation.codec() != null) {
        throw new IllegalStateException("Closing the body of " + response
            + " didn't close its backing stream. Bad interceptor?");
      }

      request = followUp;
      priorResponse = response;
    }
  }

• 1、創建StreamAllocation對象
• 2、調用RealInterceptorChainrealChain.proceed(request, streamAllocation, null, null); 進行網絡請求和調用下一個攔截器
• 3、根據異常和響應結果判斷是否重連pan
• 4、調用下一個攔截器,對response進行處理,返回給上一個攔截器

繼續下一個攔截器

將繼續執行下一個連接器BridgeInterceptor