OKHttp原始碼解析(6)----攔截器CallServerInterceptor

摘要： This is the last interceptor in the chain. It makes a network call to the server. 這是鏈中最後一個攔截器，它向伺服器發起了一次網路訪問 請求服務攔截器，負責向伺服器傳送請求資料、從伺服器讀取響應資料 原始...

This is the last interceptor in the chain. It makes a network call to the server. 這是鏈中最後一個攔截器，它向伺服器發起了一次網路訪問

請求服務攔截器，負責向伺服器傳送請求資料、從伺服器讀取響應資料

原始碼解析

@Override public Response intercept(Chain chain) throws IOException {
RealInterceptorChain realChain = (RealInterceptorChain) chain;
HttpCodec httpCodec = realChain.httpStream();
StreamAllocation streamAllocation = realChain.streamAllocation();
RealConnection connection = (RealConnection) realChain.connection();
Request request = realChain.request();

long sentRequestMillis = System.currentTimeMillis();
// 整理請求頭並寫入
httpCodec.writeRequestHeaders(request);

Response.Builder responseBuilder = null;
// 檢查是否為有 body 的請求方法
if (HttpMethod.permitsRequestBody(request.method()) && request.body() != null) {
// If there is a "Expect: 100-continue" header on the request, wait for a "HTTP/1.1 100
// Continue" response before transmitting the request body. If we do not get that, return what
// we did get (such as a 4xx response) without ever transmitting the request body.
// 如果有 Expect: 100-continue在請求頭中，那麼要等伺服器的響應。100-continue協議需要在post資料前，
徵詢伺服器情況，看伺服器是否處理POST的資料
if ("100-continue".equalsIgnoreCase(request.header("Expect"))) {
//傳送100-continue的請求
httpCodec.flushRequest();
//如果有中間級的響應，返回null
responseBuilder = httpCodec.readResponseHeaders(true);
}

if (responseBuilder == null) {
// Write the request body if the "Expect: 100-continue" expectation was met.
// 寫入請求體
Sink requestBodyOut = httpCodec.createRequestBody(request, request.body().contentLength());
BufferedSink bufferedRequestBody = Okio.buffer(requestBodyOut);
request.body().writeTo(bufferedRequestBody);
bufferedRequestBody.close();
} else if (!connection.isMultiplexed()) {
// If the "Expect: 100-continue" expectation wasn't met, prevent the HTTP/1 connection from
// being reused. Otherwise we're still obligated to transmit the request body to leave the
// connection in a consistent state.
streamAllocation.noNewStreams();
}
}
//傳送最終的請求
httpCodec.finishRequest();
// 得到響應頭
if (responseBuilder == null) {
responseBuilder = httpCodec.readResponseHeaders(false);
}

Response response = responseBuilder
.request(request)
.handshake(streamAllocation.connection().handshake())
.sentRequestAtMillis(sentRequestMillis)
.receivedResponseAtMillis(System.currentTimeMillis())
.build();

int code = response.code();
// 如果為 web socket 且狀態碼是 101 ，那麼 body 為空
if (forWebSocket && code == 101) {
// Connection is upgrading, but we need to ensure interceptors see a non-null response body.
response = response.newBuilder()
.body(Util.EMPTY_RESPONSE)
.build();
} else {
response = response.newBuilder()
.body(httpCodec.openResponseBody(response))
.build();
}
// 如果請求頭中有 close 那麼斷開連線
if ("close".equalsIgnoreCase(response.request().header("Connection"))
|| "close".equalsIgnoreCase(response.header("Connection"))) {
streamAllocation.noNewStreams();
}
// 丟擲協議異常
if ((code == 204 || code == 205) && response.body().contentLength() > 0) {
throw new ProtocolException(
"HTTP " + code + " had non-zero Content-Length: " + response.body().contentLength());
}

return response;
}

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