okhttp源码简单流程分析

拦截器详细解析可以看大佬简书 "https://www.jianshu.com/p/6fac73f7570f"和 “https://www.jianshu.com/p/3c740829475c”

okhttp请求流程
1：OkHttpClient okHttpClient = new OkHttpClient.Builder()
构建一个okhttpClient对象，传入你想传入的对象，不传就是默认的；
2：构建request对象
Request request = new Request.Builder()
3：okHttpClient.newCall 实际上返回的realCall类 继续调用RealCall.newRealCall
4：调用enqueue方法，传入我们需要的回调接口，而且会判断，
synchronized (this) {
if (executed) throw new IllegalStateException(“Already Executed”);
executed = true;
}
如果当前这个call对象已经被运行的话，则抛出异常；
5：继续调用dispatcher的enqueue方法，如果当前运行队列<64并且正在运行，访问同一个服务器地址的请求<5
就直接添加到运行队列，并且开始运行；
不然就添加到等待队列；
6：运行AsyncCall，调用它的execute方法
7：在execute方法中处理完response之后，会在finally中调用dispathcer的finished方法；
8：当当前已经处理完毕的call从运行队列中移除掉；并且调用promoteCalls方法
9：promoteCalls方法中进行判断，
如果运行队列数目大于等于64，如果等待队列里啥都没有，也直接return？
循环等待队列，
将等待队列中的数据进行移除，移除是根据运行队列中还能存放多少来决定；
移到了运行队列中，并且开始运行；

OkHttpClient okHttpClient = new OkHttpClient.Builder().build();Request request = new Request.Builder().build();//newCall方法是调用RealCall的newRealCall返回一个RealCallCall call = okHttpClient.newCall(request);//执行请求call.enqueue(new Callback() {@Overridepublic void onFailure(Call call, IOException e) {}@Overridepublic void onResponse(Call call, Response response) throws IOException {}});//这里第二次执行会直接报IllegalStateException错误并提示Already Executedcall.enqueue(new Callback() {@Overridepublic void onFailure(Call call, IOException e) {}@Overridepublic void onResponse(Call call, Response response) throws IOException {}});

进入call.enqueue方法

@Override public void enqueue(Callback responseCallback) {//这个锁是为了防止重复请求 如果你同一个call enqueue多次就会直接返回Already Executedsynchronized (this) {if (executed) throw new IllegalStateException("Already Executed");executed = true;}captureCallStackTrace();eventListener.callStart(this);//这里的enqueue是传入任务线程AsyncCall并分配到运行队列或等待队列client.dispatcher().enqueue(new AsyncCall(responseCallback));}

进入enqueue方法

//okhttp里执行任务分为两个队列 运行队列和等待队列
synchronized void enqueue(AsyncCall call) {//当运行的队列中的数值小于64， //并且同时访问同一个机器目标HOST请求书小于5直接加入到运行队列不然的话就加入到等待队列if (runningAsyncCalls.size() < maxRequests && runningCallsForHost(call) < maxRequestsPerHost) {runningAsyncCalls.add(call);//这里维护着请求用的线程池executorService().execute(call);} else {readyAsyncCalls.add(call);}}

  public synchronized ExecutorService executorService() {if (executorService == null) {//1：核心线程数 保持在线程池中的线程数量//2：线程池最大可容纳的线程数  //3参数：当线程池中的线程数量大于核心线程数，空闲线程就会等待60s才会被终止，如果小于就会立刻停止；executorService = new ThreadPoolExecutor(0, Integer.MAX_VALUE, 60, TimeUnit.SECONDS,new SynchronousQueue<Runnable>(), Util.threadFactory("OkHttp Dispatcher", false));}return executorService;}

//这个就是队列中传入的线程NameRunnable继承自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;}//这个就是Async的run方法@Override protected void execute() {boolean signalledCallback = false;try {//getResponseWithInterceptorChain() 添加拦截器 okhttp的责任链设计也在这里//response就是请求结果Response response = getResponseWithInterceptorChain();//判断重试/重定向拦截器是否被关闭if (retryAndFollowUpInterceptor.isCanceled()) {signalledCallback = true;responseCallback.onFailure(RealCall.this, new IOException("Canceled"));} else {signalledCallback = true;//返回结果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 {//将执行完成的任务从队列中移除client.dispatcher().finished(this);}}}

添加拦截器

//添加拦截器 责任链设计 
//拦截器详细解析可以看大佬简书 "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());//重试/重定向拦截器 连接失败后进行重试、对请求结果跟进后进行重定向interceptors.add(retryAndFollowUpInterceptor);//桥拦截器：连接应用程序和服务器的桥梁，我们发出的请求会经过它的处理才能发给服务器，//比如设置请求内容的长度 封装header属性 host keep-live gzip header 进行基本设置，interceptors.add(new BridgeInterceptor(client.cookieJar()));//缓存拦截器 在发出请求前，先判断是否命中缓存，//如果命中则可以不请求，直接使用缓存的响应（默认只会对Get请求进行缓存）；//如果未命中则进行网络请求，并将结果缓存，等待下次请求被命中。interceptors.add(new CacheInterceptor(client.internalCache()));//连接拦截器 与服务器建立连接。interceptors.add(new ConnectInterceptor(client));if (!forWebSocket) {interceptors.addAll(client.networkInterceptors());}//与服务器通信；封装请求数据与解析响应数据(如：HTTP报文)。interceptors.add(new CallServerInterceptor(forWebSocket));Interceptor.Chain chain = new RealInterceptorChain(interceptors, null, null, null, 0,originalRequest, this, eventListener, client.connectTimeoutMillis(),client.readTimeoutMillis(), client.writeTimeoutMillis());//执行拦截器return chain.proceed(originalRequest);}

在execute方法中处理完response之后，会在finally中调用dispathcer的finished方法；

//将当前已经处理完毕的call从运行队列中移除掉；并且调用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方法中进行判断

//如果运行队列数目大于等于64，如果等待队列里啥都没有，也直接return
//循环等待队列，
//将等待队列中的数据进行移除，移除是根据运行队列中还能存放多少来决定；
//移到了运行队列中，并且开始运行；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.}}