攔截器詳細解析可以看大佬簡書 "https://www.jianshu.com/p/6fac73f7570f"和 “https://www.jianshu.com/p/3c740829475c”

okhttp請求流程
1：OkHttpClient okHttpClient = new OkHttpClient.Builder()
構建一個okhttpClient對象，傳入你想傳入的對象，不傳就是默認的；
2：構建request對象
Request request = new Request.Builder()
3：okHttpClient.newCall 實際上返回的realCall類 繼續調用RealCall.newRealCall
4：調用enqueue方法，傳入我們需要的回調接口，而且會判斷，
synchronized (this) {
if (executed) throw new IllegalStateException(“Already Executed”);
executed = true;
}
如果當前這個call對象已經被運行的話，則拋出異常；
5：繼續調用dispatcher的enqueue方法，如果當前運行隊列<64并且正在運行，訪問同一個服務器地址的請求<5
就直接添加到運行隊列，并且開始運行；
不然就添加到等待隊列；
6：運行AsyncCall，調用它的execute方法
7：在execute方法中處理完response之后，會在finally中調用dispathcer的finished方法；
8：當當前已經處理完畢的call從運行隊列中移除掉；并且調用promoteCalls方法
9：promoteCalls方法中進行判斷，
如果運行隊列數目大于等于64，如果等待隊列里啥都沒有，也直接return？
循環等待隊列，
將等待隊列中的數據進行移除，移除是根據運行隊列中還能存放多少來決定；
移到了運行隊列中，并且開始運行；

OkHttpClient okHttpClient = new OkHttpClient.Builder().build();Request request = new Request.Builder().build();//newCall方法是調用RealCall的newRealCall返回一個RealCallCall call = okHttpClient.newCall(request);//執行請求call.enqueue(new Callback() {@Overridepublic void onFailure(Call call, IOException e) {}@Overridepublic void onResponse(Call call, Response response) throws IOException {}});//這里第二次執行會直接報IllegalStateException錯誤并提示Already Executedcall.enqueue(new Callback() {@Overridepublic void onFailure(Call call, IOException e) {}@Overridepublic void onResponse(Call call, Response response) throws IOException {}});

進入call.enqueue方法

@Override public void enqueue(Callback responseCallback) {//這個鎖是為了防止重復請求 如果你同一個call enqueue多次就會直接返回Already Executedsynchronized (this) {if (executed) throw new IllegalStateException("Already Executed");executed = true;}captureCallStackTrace();eventListener.callStart(this);//這里的enqueue是傳入任務線程AsyncCall并分配到運行隊列或等待隊列client.dispatcher().enqueue(new AsyncCall(responseCallback));}

進入enqueue方法

//okhttp里執行任務分為兩個隊列 運行隊列和等待隊列
synchronized void enqueue(AsyncCall call) {//當運行的隊列中的數值小于64， //并且同時訪問同一個機器目標HOST請求書小于5直接加入到運行隊列不然的話就加入到等待隊列if (runningAsyncCalls.size() < maxRequests && runningCallsForHost(call) < maxRequestsPerHost) {runningAsyncCalls.add(call);//這里維護著請求用的線程池executorService().execute(call);} else {readyAsyncCalls.add(call);}}

  public synchronized ExecutorService executorService() {if (executorService == null) {//1：核心線程數 保持在線程池中的線程數量//2：線程池最大可容納的線程數  //3參數：當線程池中的線程數量大于核心線程數，空閑線程就會等待60s才會被終止，如果小于就會立刻停止；executorService = new ThreadPoolExecutor(0, Integer.MAX_VALUE, 60, TimeUnit.SECONDS,new SynchronousQueue<Runnable>(), Util.threadFactory("OkHttp Dispatcher", false));}return executorService;}

//這個就是隊列中傳入的線程NameRunnable繼承自Runnable
final class AsyncCall extends NamedRunnable {private final Callback responseCallback;AsyncCall(Callback responseCallback) {super("OkHttp %s", redactedUrl());this.responseCallback = responseCallback;}String host() {return originalRequest.url().host();}Request request() {return originalRequest;}RealCall get() {return RealCall.this;}//這個就是Async的run方法@Override protected void execute() {boolean signalledCallback = false;try {//getResponseWithInterceptorChain() 添加攔截器 okhttp的責任鏈設計也在這里//response就是請求結果Response response = getResponseWithInterceptorChain();//判斷重試/重定向攔截器是否被關閉if (retryAndFollowUpInterceptor.isCanceled()) {signalledCallback = true;responseCallback.onFailure(RealCall.this, new IOException("Canceled"));} else {signalledCallback = true;//返回結果responseCallback.onResponse(RealCall.this, response);}} catch (IOException e) {if (signalledCallback) {// Do not signal the callback twice!Platform.get().log(INFO, "Callback failure for " + toLoggableString(), e);} else {eventListener.callFailed(RealCall.this, e);responseCallback.onFailure(RealCall.this, e);}} finally {//將執行完成的任務從隊列中移除client.dispatcher().finished(this);}}}

添加攔截器

//添加攔截器 責任鏈設計 
//攔截器詳細解析可以看大佬簡書 "https://www.jianshu.com/p/6fac73f7570f"和 "https://www.jianshu.com/p/3c740829475c"
Response getResponseWithInterceptorChain() throws IOException {// Build a full stack of interceptors.List<Interceptor> interceptors = new ArrayList<>();interceptors.addAll(client.interceptors());//重試/重定向攔截器 連接失敗后進行重試、對請求結果跟進后進行重定向interceptors.add(retryAndFollowUpInterceptor);//橋攔截器：連接應用程序和服務器的橋梁，我們發出的請求會經過它的處理才能發給服務器，//比如設置請求內容的長度 封裝header屬性 host keep-live gzip header 進行基本設置，interceptors.add(new BridgeInterceptor(client.cookieJar()));//緩存攔截器 在發出請求前，先判斷是否命中緩存，//如果命中則可以不請求，直接使用緩存的響應（默認只會對Get請求進行緩存）；//如果未命中則進行網絡請求，并將結果緩存，等待下次請求被命中。interceptors.add(new CacheInterceptor(client.internalCache()));//連接攔截器 與服務器建立連接。interceptors.add(new ConnectInterceptor(client));if (!forWebSocket) {interceptors.addAll(client.networkInterceptors());}//與服務器通信；封裝請求數據與解析響應數據(如：HTTP報文)。interceptors.add(new CallServerInterceptor(forWebSocket));Interceptor.Chain chain = new RealInterceptorChain(interceptors, null, null, null, 0,originalRequest, this, eventListener, client.connectTimeoutMillis(),client.readTimeoutMillis(), client.writeTimeoutMillis());//執行攔截器return chain.proceed(originalRequest);}

在execute方法中處理完response之后，會在finally中調用dispathcer的finished方法；

//將當前已經處理完畢的call從運行隊列中移除掉；并且調用promoteCalls方法
private <T> void finished(Deque<T> calls, T call, boolean promoteCalls) {int runningCallsCount;Runnable idleCallback;synchronized (this) {if (!calls.remove(call)) throw new AssertionError("Call wasn't in-flight!");if (promoteCalls) promoteCalls();runningCallsCount = runningCallsCount();idleCallback = this.idleCallback;}if (runningCallsCount == 0 && idleCallback != null) {idleCallback.run();}}

promoteCalls方法中進行判斷

//如果運行隊列數目大于等于64，如果等待隊列里啥都沒有，也直接return
//循環等待隊列，
//將等待隊列中的數據進行移除，移除是根據運行隊列中還能存放多少來決定；
//移到了運行隊列中，并且開始運行；private void promoteCalls() {if (runningAsyncCalls.size() >= maxRequests) return; // Already running max capacity.if (readyAsyncCalls.isEmpty()) return; // No ready calls to promote.for (Iterator<AsyncCall> i = readyAsyncCalls.iterator(); i.hasNext(); ) {AsyncCall call = i.next();if (runningCallsForHost(call) < maxRequestsPerHost) {i.remove();runningAsyncCalls.add(call);executorService().execute(call);}if (runningAsyncCalls.size() >= maxRequests) return; // Reached max capacity.}}