前言：为什么有些人宁愿吃生活的苦也不愿吃学习的苦，大概是因为懒惰吧，学习的苦是需要自己主动去吃的，而生活的苦，你躺着不动它就会来找你了。

一、概述

OKHttp是一个非常优秀的网络请求框架，已经被谷歌加入到Android源码中，目前比较流行的Retrofit底层也是使用OKHttp的，OKHttp的使用是要掌握的，有不懂得可以参考我的博客OKHttp3的使用和详解

在早期版本中，OKHttp支持http1.0,1.1,SPDY协议，但是http2的协议问世也导致了OKHttp做出了改变，OKHttp鼓励开发者使用http2，不再对SPDY协议给予支持，另外，新版的okhttp还支持WebScoket，这样就可以非常方便地建立长连接了。

作为非常优秀的网络请求框架，okhttp也支持网络缓存，okhttp的缓存基于DiskLruCache，DiskLruCache虽然没有被加入到Android源码中，但是也是一个非常优秀的缓存框架，有时间可以学习一下。在安全方面，okhttp支持如上图所示的TLS版本，以确保一个安全的Scoket链接，此外还支持网络链接失败的重试以及重定向。

二、源码分析

2.1 okhttp的使用

         OkHttpClient okHttpClient = new OkHttpClient();//通过Builder辅助类构建请求对象Request request = new Request.Builder().get()//get请求.url("https://www.baidu.com")//请求地址.build();//构建//通过mOkHttpClient调用请求得到Callfinal Call call = mOkHttpClient.newCall(request);//执行同步请求，获取Response对象Response response = call.execute();String string = response.body().string();Log.e(TAG, "get同步请求success==" + string);//异步执行call.enqueue(new Callback() {@Overridepublic void onFailure(@NotNull Call call, @NotNull IOException e) {Log.e(TAG, "get异步请求failure==" + e.getMessage());}@Overridepublic void onResponse(@NotNull Call call, @NotNull Response response) throws IOException {String string = response.body().string();Log.e(TAG, "get异步请求success==" + string);}});

2.2 同步Request的请求流程

在开始流程讲解前先来了解三个概念（注释来自于源码）：

Connections：链接远程服务器的无理链接

Streams：基于Connection的逻辑Http请求/响应对。一个链接可以承载多个Stream都是有限制的，http1.0、1.1只支持承载一个Stream，http2支持承载多个Stream(支持并发请求，并发请求共用一个Connection)

Calls：逻辑Stream序列，典型的例子是一个初始请求以及后续的请求。对于同步和异步请求，唯一的区别就是异步请求会放到线程池（ThreadPoolExecutor）中执行，而同步请求会在当前线程执行，会阻塞当前线程。

call：最终的请求对象

Interceptors：这个是okhttp最核心的部分，一个请求会经过okhttp若干个拦截器的处理，每一个拦截器都完成一个功能模块，一个Request经过拦截器的处理后，最终会得到Response。拦截器里面包含的东西很多，这里将重点讲解。

2.3 OkHttpClient

首先，我们构造OkHttpClient对象实例，OkHttpClient创建实例的方式有两种，第一种是使用默认构造函数直接new一个实例，另一种就是，通过建造者(Builder)模式new OkHttpClient().Builder().build，这两种方式有什么区别呢？其实第二种默认的设置和第一种相同，但是我们可以利用建造者模式来设置每一种属性。

我们先来看第一种方式：OkHttpClient okHttpClient = new OkHttpClient();

 public OkHttpClient() {this(new Builder());}public Builder() {dispatcher = new Dispatcher();protocols = DEFAULT_PROTOCOLS;connectionSpecs = DEFAULT_CONNECTION_SPECS;eventListenerFactory = EventListener.factory(EventListener.NONE);proxySelector = ProxySelector.getDefault();cookieJar = CookieJar.NO_COOKIES;socketFactory = SocketFactory.getDefault();hostnameVerifier = OkHostnameVerifier.INSTANCE;certificatePinner = CertificatePinner.DEFAULT;proxyAuthenticator = Authenticator.NONE;authenticator = Authenticator.NONE;connectionPool = new ConnectionPool();dns = Dns.SYSTEM;followSslRedirects = true;followRedirects = true;retryOnConnectionFailure = true;connectTimeout = 10_000;readTimeout = 10_000;writeTimeout = 10_000;pingInterval = 0;}

可以看到简单的一句new OkHttpClient()，Okhttp就为我们做了很多工作，很多需要使用到的参数在这里获得默认值，我们来分析一下他们的含义：

dispatcher ：调度器的意识，主要作用通过双端队列保存Calls(同步/异步call)，同时在线程池中执行异步请求；
protocols：默认支持的Http协议版本，Protocol.HTTP_2/Protocol.HTTP_1_1；
connectionSpecs ：Okhttp的链接（Connection）配置，ConnectionSpec.MODERN_TLS, ConnectionSpec.CLEARTEXT，一个针对TLS链接的配置，一个针对普通的http链接配置；
eventListenerFactory：一个Call状态的监听器，这个是OKHttp新添加的功能，这个还不是最终版本，最后还会改变；
proxySelector：使用默认的代理选择器；
cookieJar：默认是没有Cookie的；
socketFactory：使用默认的Socket工厂生产Socket；
hostnameVerifier、certificatePinner、proxyAuthenticator、authenticator：安全相关的配置；
connectionPool：连接池；
dns：域名解析系统，domain name -> ip address；
followSslRedirects、followRedirects、retryOnConnectionFailure：起始状态；
connectTimeout、readTimeout 、writeTimeout：分别为：链接超时时间、读取超时时间、写入超时时间；
pingInterval：这个就和WebSocket有关了，为了保证长连接，必须每隔一段时间发送一个ping指令进行保活。

注意事项：OkHttpClient强烈建议全局单例使用，因为每一个OkHttpClient都有自己单独的线程池和连接池，复用连接池和线程池能够减少延迟和节省内存。

2.4 RealCall(生成一个Call)

在我们定义了请求对象Request之后，通过okHttpClient.newCall()生成一个Call，该对象代表一个执行的请求，Call是可以被取消的，Call对象代表一个request/response 对（Stream），一个Call只能被执行一次，执行同步请求（call.execute()）:

 /*** Prepares the {@code request} to be executed at some point in the future.*/@Override public Call newCall(Request request) {return RealCall.newRealCall(this, request, false /* for web socket */);}static RealCall newRealCall(OkHttpClient client, Request originalRequest, boolean forWebSocket) {// Safely publish the Call instance to the EventListener.RealCall call = new RealCall(client, originalRequest, forWebSocket);call.eventListener = client.eventListenerFactory().create(call);return call;}@Override public Response execute() throws IOException {synchronized (this) {if (executed) throw new IllegalStateException("Already Executed");executed = true;}captureCallStackTrace();eventListener.callStart(this);try {client.dispatcher().executed(this);Response result = getResponseWithInterceptorChain();if (result == null) throw new IOException("Canceled");return result;} catch (IOException e) {eventListener.callFailed(this, e);throw e;} finally {client.dispatcher().finished(this);}}

若果executed = true说明已经执行了，如果再次调用就会抛出异常，这里说明一个Call只能被执行一次，注意同步执行请求和异步执行请求的区别：异步执行请求（call.equeue(CallBack callback)）

 @Override public void enqueue(Callback responseCallback) {synchronized (this) {if (executed) throw new IllegalStateException("Already Executed");executed = true;}captureCallStackTrace();eventListener.callStart(this);client.dispatcher().enqueue(new AsyncCall(responseCallback));}

可以看到同步执行请求生成的是RealCall，而异步执行请求生成的是AsyncCall，AsyncCall其实就是Runnable的子类，如果可以执行则对当前添加监听操作，然后将Call对象放入调度器（dispatcher）中，最后由拦截器中的各个拦截器对该请求进行处理，最终返回Response。

2.5 调度器（dispatcher）

在上面同步执行请求中看到client.dispatcher().executed(this)后由Response result = getResponseWithInterceptorChain()返回结果，最后执行finished()方法，我们先来看看client.dispatcher().executed(this)。

调度器（dispatcher）是保存同步和异步Call的地方，并负责执行异步AsyncCall。我们来看看维护的变量含义：

int maxRequests = 64：最大并发请求数为64
int maxRequestsPerHost = 5：每个主机的最大请求数为5
Runnable idleCallback：Runnable对象，在删除请求时执行
ExecutorService executorService：线程池
Deque<AsyncCall> readyAsyncCalls：缓存异步调用准备的任务
Deque<AsyncCall> runningAsyncCalls：缓存正在运行的异步任务，包括取消尚未完成的任务
Deque<RealCall> runningSyncCalls：缓存正在运行的同步任务，包括取消尚未完成的任务

如上图，针对同步请求Dispatcher使用一个Deque保存了同步请求任务；针对异步Dispacher使用了两个Deque保存任务，一个保存准备执行的请求，一个保存正在执行的请求，为什么要两个呢？因为Dispatch默认支持并发请求是64个，单个Host最多执行5个并发请求，如果超过，则call会被放入readyAsyncCalls中，当出现空闲线程时，再讲readyAsyncCalls中的线程移到runningAsyncCalls中，执行请求。

那么client.dispatcher().executed(this)里面做了什么呢？

  @Override public Response execute() throws IOException {······client.dispatcher().executed(this);Response result = getResponseWithInterceptorChain();return result;} catch (IOException e) {·····} finally {client.dispatcher().finished(this);}}

  /** Used by {@code Call#execute} to signal it is in-flight. */synchronized void executed(RealCall call) {runningSyncCalls.add(call);}

里面只是将同步任务加入到runningSyncCalls中，由Response result = getResponseWithInterceptorChain()拦截器拦截后返回Response 结果，最后执行finished()方法。

  /** Used by {@code Call#execute} to signal completion. */void finished(RealCall call) {finished(runningSyncCalls, call, false);}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!");//移除集合中的请求if (promoteCalls) promoteCalls();runningCallsCount = runningCallsCount();idleCallback = this.idleCallback;}if (runningCallsCount == 0 && idleCallback != null) {idleCallback.run();}}

对于同步请求，只是简单地在runningSyncCalls集合中移除请求，promoteCalls为false，因此不会执行promoteCalls()中的方法，promoteCalls()里面主要是遍历并执行异步请求待执行合集中的请求。下面来看看异步执行中的方法：

  synchronized void enqueue(AsyncCall call) {if (runningAsyncCalls.size() < maxRequests && runningCallsForHost(call) < maxRequestsPerHost) {runningAsyncCalls.add(call);executorService().execute(call);} else {readyAsyncCalls.add(call);}}

可以看到当“正在执行的请求总数<64 && 单个Host真正执行的请求<5”则将请求加入到runningAsyncCalls执行中的集合中，然后利用线程池执行该请求，否则就直接加入到readyAsyncCalls准备执行的集合中。因为AsyncCall 是Runnable的子类，在线程池中最终会调用AsyncCall.execute()方法执行异步请求。

   @Override protected void execute() {boolean signalledCallback = false;try {Response response = getResponseWithInterceptorChain();//拦截器if (retryAndFollowUpInterceptor.isCanceled()) {//如果拦截失败回调onFailure方法signalledCallback = true;responseCallback.onFailure(RealCall.this, new IOException("Canceled"));} else {signalledCallback = true;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 {client.dispatcher().finished(this);//结束}}}

此处的执行逻辑跟同步的大致相同，只是client.dispatcher().finished(this)不一样，这是一个异步任务，会回调另外一个finish()方法：

  /** Used by {@code AsyncCall#run} to signal completion. */void finished(AsyncCall call) {finished(runningAsyncCalls, call, true);}private <T> void finished(Deque<T> calls, T call, boolean promoteCalls) {·····synchronized (this) {if (!calls.remove(call)) throw new AssertionError("Call wasn't in-flight!");//移除出请求集合if (promoteCalls) promoteCalls();runningCallsCount = runningCallsCount();idleCallback = this.idleCallback;}·····}

可以看到promoteCalls为true，所以会执行promoteCalls()方法，

  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.}}

这个方法主要是遍历readyAsyncCalls集合中待执行请求，如果runningAsyncCalls的任务数<64并且readyAsyncCalls不为空，将readyAsyncCalls准备执行的集合请求加入到runningAsyncCalls中并且执行请求。如果runningAsyncCalls的任务数>=64，则说明正在执行的任务池已经满了，暂时无法加入；如果readyAsyncCalls集合为空，说明请求都已经执行了，没有还没执行的请求。放入readyAsyncCalls集合的请求会继续走上述的流程，直至到所有的请求被执行。

2.6 拦截器Intercepoter

我们回到最重要的地方拦截器部分：

Response response = 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, this, eventListener, client.connectTimeoutMillis(),client.readTimeoutMillis(), client.writeTimeoutMillis());return chain.proceed(originalRequest);}

这里先介绍一个比较重要的类：RealInterceptorChain，拦截器链，所有拦截器的合集，网络的核心也是最后的调用者。

可以看到上面依次添加interceptors，retryAndFollowUpInterceptor，BridgeInterceptor，CacheInterceptor，ConnectInterceptor到RealInterceptorChain中，拦截器之所以可以依次调用，并最终从后先前返回Response，都是依赖chain.proceed(originalRequest)这个方法，

 @Override public Response proceed(Request request) throws IOException {return proceed(request, streamAllocation, httpCodec, connection);}public Response proceed(Request request, StreamAllocation streamAllocation, HttpCodec httpCodec,·····// Call the next interceptor in the chain.RealInterceptorChain next = new RealInterceptorChain(interceptors, streamAllocation, httpCodec,connection, index + 1, request, call, eventListener, connectTimeout, readTimeout,writeTimeout);Interceptor interceptor = interceptors.get(index);Response response = interceptor.intercept(next);······return response;}

执行当前的拦截器intercept(RealInterceptorChain next)方法，并且调用下一个（index+1）拦截器，下一个拦截器的调用依赖于当前拦截器的intercept()方法中，对RealInterceptorChain的proceed()方法的调用：

response = realChain.proceed(request, streamAllocation, null, null);

可以看到当前拦截器的Response依赖于一下一个拦截器的Response，因此沿着这条拦截器链会依次调用下一个拦截器，执行到最后一哥拦截器的时候，就会沿着相反方向依次返回Response，得到最终的Response。

2.7 RetryAndFollowUpInterceptor：重试及重定向拦截器

拦截器类都是继承Interceptor类，并重写intercept(Chain chain)方法：

@Override
public Response intercept(Chain chain) throws IOException {Request request = chain.request();//获取Request对象RealInterceptorChain realChain = (RealInterceptorChain) chain;//获取拦截器对象，用于调用下一个proceed（）Call call = realChain.call();EventListener eventListener = realChain.eventListener();streamAllocation = new StreamAllocation(client.connectionPool(), createAddress(request.url()),call, eventListener, callStackTrace);int followUpCount = 0;Response priorResponse = null;while (true) {//循环if (canceled) {streamAllocation.release();throw new IOException("Canceled");}Response response;boolean releaseConnection = true;try {response = realChain.proceed(request, streamAllocation, null, null);//调用下一个拦截器releaseConnection = false;} catch (RouteException e) {// The attempt to connect via a route failed. The request will not have been sent.if (!recover(e.getLastConnectException(), false, request)) {//路由异常，尝试恢复，如果再失败就跑出异常throw e.getLastConnectException();}releaseConnection = false;continue;//继续重试} 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;//链接关闭异常，尝试恢复releaseConnection = false;continue;//继续重试} 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) {//前一个重试得到的responseresponse = response.newBuilder().priorResponse(priorResponse.newBuilder().body(null).build()).build();}//主要为了新的重试Request添加验证头等内容Request followUp = followUpRequest(response);if (followUp == null) {//如果一个响应的到的code是200，那么followUp==nullif (!forWebSocket) {streamAllocation.release();}return response;}//----------------异常处理----------------------closeQuietly(response.body());if (++followUpCount > MAX_FOLLOW_UPS) {//超出最大次数，抛出异常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;//得到处理后的Request,沿着拦截链继续请求priorResponse = response;}}

该拦截器的作用就是重试以及重定向，当一个请求由于各种原因失败，或者路由异常，则尝试恢复，否则根据响应码ResponseCode在followUpRequest(response)方法中对Request进行再处理得到行的Request，然后沿着拦截器继续新的请求，如果ResponseCode==200，那么这些过程就结束了。

2.8 BridgeInterceptor：桥拦截器

BridgeInterceptor的主要作用是为请求Request添加请求头，为响应Response添加响应头：

 @Override
public Response intercept(Chain chain) throws IOException {Request userRequest = chain.request();Request.Builder requestBuilder = userRequest.newBuilder();//----------------Request---------------------RequestBody body = userRequest.body();if (body != null) {MediaType contentType = body.contentType();if (contentType != null) {//添加Content-Type请求头requestBuilder.header("Content-Type", contentType.toString());}long contentLength = body.contentLength();if (contentLength != -1) {requestBuilder.header("Content-Length", Long.toString(contentLength));requestBuilder.removeHeader("Transfer-Encoding");} else {requestBuilder.header("Transfer-Encoding", "chunked");//分块传输requestBuilder.removeHeader("Content-Length");}}if (userRequest.header("Host") == null) {requestBuilder.header("Host", hostHeader(userRequest.url(), false));}if (userRequest.header("Connection") == null) {requestBuilder.header("Connection", "Keep-Alive");}// If we add an "Accept-Encoding: gzip" header field we're responsible for also decompressing// the transfer stream.boolean transparentGzip = false;if (userRequest.header("Accept-Encoding") == null && userRequest.header("Range") == null) {transparentGzip = true;requestBuilder.header("Accept-Encoding", "gzip");}List<Cookie> cookies = cookieJar.loadForRequest(userRequest.url());if (!cookies.isEmpty()) {requestBuilder.header("Cookie", cookieHeader(cookies));}if (userRequest.header("User-Agent") == null) {requestBuilder.header("User-Agent", Version.userAgent());}Response networkResponse = chain.proceed(requestBuilder.build());//----------------Response---------------------HttpHeaders.receiveHeaders(cookieJar, userRequest.url(), networkResponse.headers());//保存cookieResponse.Builder responseBuilder = networkResponse.newBuilder().request(userRequest);if (transparentGzip&& "gzip".equalsIgnoreCase(networkResponse.header("Content-Encoding"))&& HttpHeaders.hasBody(networkResponse)) {GzipSource responseBody = new GzipSource(networkResponse.body().source());Headers strippedHeaders = networkResponse.headers().newBuilder().removeAll("Content-Encoding").removeAll("Content-Length")//Content-Encoding和Content-Length不能用于gzip解压.build();responseBuilder.headers(strippedHeaders);String contentType = networkResponse.header("Content-Type");responseBuilder.body(new RealResponseBody(contentType, -1L, Okio.buffer(responseBody)));}return responseBuilder.build();}

这个拦截器相对比较简单。

2.9 CacheInterceptor：缓存拦截器

我们先来看看缓存的响应头：

Cache-control：标明缓存最大的存活时常；

Date：服务器告诉客户端，该资源发送的时间；

Expires：表示过期时间（该字段是1.0的东西，与cache-control同时存在时，cache-control的优先级更高）；

Last-Modified：服务器告诉客户端，资源最后的修改时间；

E-Tag：当前资源在服务器的唯一标识，用于判断资源是否被修改。

还有If-Modified-since和If-none-Match两个字段，这两个字段是配合Last-Modified和E-Tag使用的，大致流程如下：服务器收到请求时，会在200 OK中返回该资源的Last-Modified和ETag头（服务器支持缓存的时候才有这两个头），客户端将该资源保存在cache中，并且记录这两个属性，当客户端需要发送相同的请求时，根据Date + Cache-control来判断缓存是否过期，如果过期了则会在请求中携带If-Modified-Since和If-None-Match两个头，这两个头的值分别是Last-Modified和ETag头的值，服务器通过这两个头判断资源未发生变化，客户端重新加载，返回304响应。

先来看看CacheInterceptor几个比较重要的类：

CacheStrategy：缓存策略类，告诉CacheInterceptor是使用缓存还是使用网络请求；
Cache：封装了实际的缓存操作；
DiskLruCache：Cache基于DiskLruCache。

@Override public Response intercept(Chain chain) throws IOException {Response cacheCandidate = cache != null? cache.get(chain.request())//以请求的URL作为可以来获取缓存: null;long now = System.currentTimeMillis();//缓存策略类，该类决定了是使用缓存还是网络请求CacheStrategy strategy = new CacheStrategy.Factory(now, chain.request(), cacheCandidate).get();Request networkRequest = strategy.networkRequest;//网络请求，如果为null则代表不适用网络请求Response cacheResponse = strategy.cacheResponse;//缓存响应，如果为null则表示不适用缓存if (cache != null) {//根据缓存策略，更新统计指标：请求次数，使用网络请求次数，缓存次数cache.trackResponse(strategy);}//缓存不可用，关闭if (cacheCandidate != null && cacheResponse == null) {closeQuietly(cacheCandidate.body()); // The cache candidate wasn't applicable. Close it.}//如果既无网络可用，也无缓存可用，则返回504错误// If we're forbidden from using the network and the cache is insufficient, fail.if (networkRequest == null && cacheResponse == null) {return new Response.Builder().request(chain.request()).protocol(Protocol.HTTP_1_1).code(504).message("Unsatisfiable Request (only-if-cached)").body(Util.EMPTY_RESPONSE).sentRequestAtMillis(-1L).receivedResponseAtMillis(System.currentTimeMillis()).build();}//缓存可用，直接使用缓存// If we don't need the network, we're done.if (networkRequest == null) {return cacheResponse.newBuilder().cacheResponse(stripBody(cacheResponse)).build();}Response networkResponse = null;try {//进行网络请求，得到网络响应networkResponse = chain.proceed(networkRequest);} finally {// If we're crashing on I/O or otherwise, don't leak the cache body.if (networkResponse == null && cacheCandidate != null) {closeQuietly(cacheCandidate.body());}}//HTTP_NOT_MODIFIED缓存有效，合并网络请求和缓存// If we have a cache response too, then we're doing a conditional get.if (cacheResponse != null) {if (networkResponse.code() == HTTP_NOT_MODIFIED) {Response response = cacheResponse.newBuilder().headers(combine(cacheResponse.headers(), networkResponse.headers())).sentRequestAtMillis(networkResponse.sentRequestAtMillis()).receivedResponseAtMillis(networkResponse.receivedResponseAtMillis()).cacheResponse(stripBody(cacheResponse)).networkResponse(stripBody(networkResponse)).build();networkResponse.body().close();// Update the cache after combining headers but before stripping the// Content-Encoding header (as performed by initContentStream()).cache.trackConditionalCacheHit();cache.update(cacheResponse, response);//更新缓存return response;} else {closeQuietly(cacheResponse.body());}}Response response = networkResponse.newBuilder().cacheResponse(stripBody(cacheResponse)).networkResponse(stripBody(networkResponse)).build();if (cache != null) {//有响应体并且可缓存if (HttpHeaders.hasBody(response) && CacheStrategy.isCacheable(response, networkRequest)) {// Offer this request to the cache.CacheRequest cacheRequest = cache.put(response);return cacheWritingResponse(cacheRequest, response);//写缓存}if (HttpMethod.invalidatesCache(networkRequest.method())) {//判断缓存的有效性try {cache.remove(networkRequest);} catch (IOException ignored) {// The cache cannot be written.}}}return response;}

再简单说一下流程：

1.如果网络不可用而且无可用的缓存，则返回504错误；

2.继续，如果不需要网络请求，则直接使用缓存；

3.继续，如果网络请求可用，则进行网络请求；

4.继续，如果有缓存，并且网络请求返回HTTP_NOT_MODIFIED，说明缓存还有效的，则合并网络响应和缓存的结果，同时更新缓存；

5.继续，如果没有缓存，则写入新的缓存。

CacheStrategy在CacheInterceptor中起到了很关键的作用，该类决定了是网络请求还是缓存，该类最关键的代码是getCandidate()方法：

 private CacheStrategy getCandidate() {// No cached response.//没有缓存，直接使用网络请求if (cacheResponse == null) {return new CacheStrategy(request, null);}//https, 但是没有握手，直接进行网络请求// Drop the cached response if it's missing a required handshake.if (request.isHttps() && cacheResponse.handshake() == null) {return new CacheStrategy(request, null);}// If this response shouldn't have been stored, it should never be used// as a response source. This check should be redundant as long as the// persistence store is well-behaved and the rules are constant.if (!isCacheable(cacheResponse, request)) {//不可以缓存，直接进行网络请求return new CacheStrategy(request, null);}CacheControl requestCaching = request.cacheControl();if (requestCaching.noCache() || hasConditions(request)) {//请求头nocache或者请求头包含If-Modified-Since或者If-None-Match//请求头包含If-Modified-Since或者If-None-Match意味着本地缓存过期，需要服务器验证//本地缓存是不是还能继续使用return new CacheStrategy(request, null);}CacheControl responseCaching = cacheResponse.cacheControl();if (responseCaching.immutable()) {//强制使用缓存return new CacheStrategy(null, cacheResponse);}long ageMillis = cacheResponseAge();long freshMillis = computeFreshnessLifetime();if (requestCaching.maxAgeSeconds() != -1) {freshMillis = Math.min(freshMillis, SECONDS.toMillis(requestCaching.maxAgeSeconds()));}long minFreshMillis = 0;if (requestCaching.minFreshSeconds() != -1) {minFreshMillis = SECONDS.toMillis(requestCaching.minFreshSeconds());}long maxStaleMillis = 0;if (!responseCaching.mustRevalidate() && requestCaching.maxStaleSeconds() != -1) {maxStaleMillis = SECONDS.toMillis(requestCaching.maxStaleSeconds());}//可缓存，并且ageMillis + minFreshMillis < freshMillis + maxStaleMillis//意味着虽过期，但是可用，在请求头添加“warning”if (!responseCaching.noCache() && ageMillis + minFreshMillis < freshMillis + maxStaleMillis) {Response.Builder builder = cacheResponse.newBuilder();if (ageMillis + minFreshMillis >= freshMillis) {builder.addHeader("Warning", "110 HttpURLConnection \"Response is stale\"");}long oneDayMillis = 24 * 60 * 60 * 1000L;if (ageMillis > oneDayMillis && isFreshnessLifetimeHeuristic()) {builder.addHeader("Warning", "113 HttpURLConnection \"Heuristic expiration\"");}return new CacheStrategy(null, builder.build());//使用缓存}// Find a condition to add to the request. If the condition is satisfied, the response body// will not be transmitted.String conditionName;String conditionValue;//走到这里说明缓存已经过期//添加请求头：If-Modified-Since或者If-None-Match//etag与If-None-Match配合使用//lastModified与If-Modified-Since配合使用//前者和后者的值是相同的//区别在于前者是响应头，后者是请求头。//后者用于服务器进行资源比对，看看是资源是否改变了。// 如果没有，则本地的资源虽过期还是可以用的if (etag != null) {conditionName = "If-None-Match";conditionValue = etag;} else if (lastModified != null) {conditionName = "If-Modified-Since";conditionValue = lastModifiedString;} else if (servedDate != null) {conditionName = "If-Modified-Since";conditionValue = servedDateString;} else {return new CacheStrategy(request, null); // No condition! Make a regular request.}Headers.Builder conditionalRequestHeaders = request.headers().newBuilder();Internal.instance.addLenient(conditionalRequestHeaders, conditionName, conditionValue);Request conditionalRequest = request.newBuilder().headers(conditionalRequestHeaders.build()).build();return new CacheStrategy(conditionalRequest, cacheResponse);}

大致的流程如下：（if-else的关系）

1.没有缓存，直接使用网络请求；

2.如果是https，但是没有握手，直接网络请求；

3.不可缓存，直接网络请求；

4.请求头nocache，或者请求头包含If-Modified-Since或者If-None-Match，则需要服务器验证本地缓存是否继续使用，直接网络请求；

5.可缓存，并且ageMillis + minFreshMillis < freshMillis + maxStaleMillis（意味着过期，但是可用，会在请求头添加warning），则使用缓存；

6.缓存过期，则添加请求头，If-Modified-Since或者If-None-Match，进行网络请求。

缓存拦截器流程图：

2.10 ConnectInterceptor（连接池拦截器）

ConnectInterceptor是一个链接相关的拦截器，这个拦截器的代码最少，但并不是最简单的，先来看看ConnectInterceptor中比较重要的相关类：

RouteDatabase：这是一个关于路由器白名单和黑名单类，处于黑名单的信息会避免不必要的尝试；

RealConnection：Connect子类，主要实现链接的建立等工作；

ConnectionPool：连接池，实现链接的复用；

Connection和Stream的关系：Http1是1:1的关系，Http2是1对多的关系；就是说一个http1.x的链接只能被一个请求使用，而一个http2.x链接对应多个Stream，多个Stream的意思是Http2连接支持并发请求，即一个链接可以被多个请求使用。还有Http1.x的keep-alive机制的作用是保证链接使用完不关闭，当下一次请求与链接的Host相同的时候，连接可以直接使用，不用创建（节省资源，提高性能）。

StreamAllocation：流分配，流是什么呢？我们知道Connection是一个连接远程服务器的Socket连接，而Stream是基于Connection逻辑Http 请求/响应对，StreamAllocation会通过ConnectionPool获取或者新生成一个RealConnection来得到一个连接到server的Connection连接，同时会生成一个HttpCodec用于下一个CallServerInterceptor，以完成最终的请求。

HttpCodec：Encodes HTTP requests and decodes HTTP responses（源码注释），大意为编码Http请求，解码Http响应。针对不同的版本OKHttp为我们提供了HttpCodec1(Http1.x)和HttpCodec2(Http2.x)。

一句话概括就是：分配一个Connection和HttpCodec，为最终的请求做准备。

/** Opens a connection to the target server and proceeds to the next interceptor. */
public final class ConnectInterceptor implements Interceptor {public final OkHttpClient client;public ConnectInterceptor(OkHttpClient client) {this.client = client;}@Override public Response intercept(Chain chain) throws IOException {RealInterceptorChain realChain = (RealInterceptorChain) chain;Request request = realChain.request();StreamAllocation streamAllocation = realChain.streamAllocation();// We need the network to satisfy this request. Possibly for validating a conditional GET.//我们需要网络来满足这个请求，可能是为了验证一个条件GET请求（缓存验证等）boolean doExtensiveHealthChecks = !request.method().equals("GET");HttpCodec httpCodec = streamAllocation.newStream(client, chain, doExtensiveHealthChecks);RealConnection connection = streamAllocation.connection();return realChain.proceed(request, streamAllocation, httpCodec, connection);}
}

代码量表面看起来很少，但是大部分都已经封装好的了，这里仅仅是调用，为了可读性和维护性，该封装的还是要封装。这里的核心代码就两行：

HttpCodec httpCodec = streamAllocation.newStream(client, chain, doExtensiveHealthChecks);
RealConnection connection = streamAllocation.connection();

可以看出，主要的工作由streamAllocation完成，我们来看看newStream()和connection()做了什么工作：

 public HttpCodec newStream(OkHttpClient client, Interceptor.Chain chain, boolean doExtensiveHealthChecks) {int connectTimeout = chain.connectTimeoutMillis();int readTimeout = chain.readTimeoutMillis();int writeTimeout = chain.writeTimeoutMillis();boolean connectionRetryEnabled = client.retryOnConnectionFailure();try {//找到一个可用链接RealConnection resultConnection = findHealthyConnection(connectTimeout, readTimeout,writeTimeout, connectionRetryEnabled, doExtensiveHealthChecks);HttpCodec resultCodec = resultConnection.newCodec(client, chain, this);synchronized (connectionPool) {codec = resultCodec;return resultCodec;}} catch (IOException e) {throw new RouteException(e);}}

可以看到最关键的一步是findHealthyConnection()，这个方法的主要作用是找到可用的链接，如果连接不可用，这个过程会一直持续哦。

  /*** Finds a connection and returns it if it is healthy. If it is unhealthy the process is repeated* until a healthy connection is found.*/private RealConnection findHealthyConnection(int connectTimeout, int readTimeout,int writeTimeout, boolean connectionRetryEnabled, boolean doExtensiveHealthChecks)throws IOException {while (true) {RealConnection candidate = findConnection(connectTimeout, readTimeout, writeTimeout,connectionRetryEnabled);// If this is a brand new connection, we can skip the extensive health checks.如果是一个新链接，直接返回就好synchronized (connectionPool) {if (candidate.successCount == 0) {return candidate;}}// Do a (potentially slow) check to confirm that the pooled connection is still good. If it// isn't, take it out of the pool and start again.if (!candidate.isHealthy(doExtensiveHealthChecks)) {//判断连接是否还是好的noNewStreams();//不是好的就移除连接池continue;//不是好的就一直持续}return candidate;}}

我们来看看你noNewStreams()做了什么操作：

  /** Forbid new streams from being created on the connection that hosts this allocation. */public void noNewStreams() {Socket socket;Connection releasedConnection;synchronized (connectionPool) {releasedConnection = connection;socket = deallocate(true, false, false);//noNewStreams，released，streamFinished核心方法if (connection != null) releasedConnection = null;}closeQuietly(socket);//关闭Socketif (releasedConnection != null) {eventListener.connectionReleased(call, releasedConnection);//监听回调}}

上面的关键代码是deallocate()：

 private Socket deallocate(boolean noNewStreams, boolean released, boolean streamFinished) {assert (Thread.holdsLock(connectionPool));//这里以noNewStreams为true，released为false，streamFinished为false为例if (streamFinished) {this.codec = null;}if (released) {this.released = true;}Socket socket = null;if (connection != null) {if (noNewStreams) {//noNewStreams是RealConnection的属性，如果为true则这个链接不会创建新的Stream，一但设置为true就一直为true//搜索整个源码，这个该属性设置地方如下：//evitAll:关闭和移除连接池中的所有链接，（如果连接空闲，即连接上的Stream数为0，则noNewStreams为true）；//pruneAndGetAllocationCount：移除内存泄漏的连接，以及获取连接Stream的分配数；//streamFailed：Stream分配失败//综上所述，这个属性的作用是禁止无效连接创建新的Stream的connection.noNewStreams = true;}if (this.codec == null && (this.released || connection.noNewStreams)) {release(connection);//释放Connection承载的StreamAllocations资源（connection.allocations）if (connection.allocations.isEmpty()) {connection.idleAtNanos = System.nanoTime();//connectionBecameIdle:通知线程池该连接是空闲连接，可以作为移除或者待移除对象if (Internal.instance.connectionBecameIdle(connectionPool, connection)) {socket = connection.socket();}}connection = null;//}}return socket;//返回待关闭的Socket对象}

我们来看看findConnection()方法：

 /*** Returns a connection to host a new stream. This prefers the existing connection if it exists,* then the pool, finally building a new connection.*/private RealConnection findConnection(int connectTimeout, int readTimeout, int writeTimeout,boolean connectionRetryEnabled) throws IOException {boolean foundPooledConnection = false;RealConnection result = null;Route selectedRoute = null;Connection releasedConnection;Socket toClose;synchronized (connectionPool) {//排除异常情况if (released) throw new IllegalStateException("released");if (codec != null) throw new IllegalStateException("codec != null");if (canceled) throw new IOException("Canceled");// Attempt to use an already-allocated connection. We need to be careful here because our// already-allocated connection may have been restricted from creating new streams.//这个方法与deallocate()方法作用一致//如果连接不能创建Stream，则释放资源，返回待关闭的close SocketreleasedConnection = this.connection;toClose = releaseIfNoNewStreams();//经过releaseIfNoNewStreams()，如果connection不为null,则连接可用if (this.connection != null) {// We had an already-allocated connection and it's good.//存在可使用的已分配连接，result = this.connection;//为null值，说明这个连接是有效的releasedConnection = null;}if (!reportedAcquired) {// If the connection was never reported acquired, don't report it as released!releasedConnection = null;}//没有可用连接，去连接池中找if (result == null) {// Attempt to get a connection from the pool.//通过ConnectionPool,Address,StreamAllocation从连接池中获取连接Internal.instance.get(connectionPool, address, this, null);if (connection != null) {foundPooledConnection = true;result = connection;} else {selectedRoute = route;}}}closeQuietly(toClose);if (releasedConnection != null) {eventListener.connectionReleased(call, releasedConnection);}if (foundPooledConnection) {eventListener.connectionAcquired(call, result);}if (result != null) {// If we found an already-allocated or pooled connection, we're done.//找到一个已分配或者连接池中的连接，此过程结束，返回return result;}//否则我们需要一个路由信心，这是一个阻塞操作// If we need a route selection, make one. This is a blocking operation.boolean newRouteSelection = false;if (selectedRoute == null && (routeSelection == null || !routeSelection.hasNext())) {newRouteSelection = true;routeSelection = routeSelector.next();}synchronized (connectionPool) {if (canceled) throw new IOException("Canceled");if (newRouteSelection) {// Now that we have a set of IP addresses, make another attempt at getting a connection from// the pool. This could match due to connection coalescing.//提供更加全面的路由信息，再次从连接池中获取连接List<Route> routes = routeSelection.getAll();for (int i = 0, size = routes.size(); i < size; i++) {Route route = routes.get(i);Internal.instance.get(connectionPool, address, this, route);if (connection != null) {foundPooledConnection = true;result = connection;this.route = route;break;}}}//实在是没有找到，只能生成新的连接if (!foundPooledConnection) {if (selectedRoute == null) {selectedRoute = routeSelection.next();}// Create a connection and assign it to this allocation immediately. This makes it possible// for an asynchronous cancel() to interrupt the handshake we're about to do.route = selectedRoute;refusedStreamCount = 0;result = new RealConnection(connectionPool, selectedRoute);acquire(result, false);//添加Connection的StreamAllocation添加到connection.allocations集合中}}// If we found a pooled connection on the 2nd time around, we're done.//如果连接是从连接池中找到的，那么说明连接是可复用的，不是新生的，新生成的连接是需要连接服务器才能可用的if (foundPooledConnection) {eventListener.connectionAcquired(call, result);return result;}// Do TCP + TLS handshakes. This is a blocking operation.连接serverresult.connect(connectTimeout, readTimeout, writeTimeout, connectionRetryEnabled, call, eventListener);routeDatabase().connected(result.route());//将路由信息添加到routeDatabase中Socket socket = null;synchronized (connectionPool) {reportedAcquired = true;// Pool the connection.Internal.instance.put(connectionPool, result);//将新生成的连接放入连接池中// If another multiplexed connection to the same address was created concurrently, then// release this connection and acquire that one.//如果是HTTP2连接，由于HTTP2连接具有多路复用特性//因此，我们需要确保http2的多路复用特性if (result.isMultiplexed()) {//确保http2的多路复用特性，重复的连接将 被踢除socket = Internal.instance.deduplicate(connectionPool, address, this);result = connection;}}closeQuietly(socket);eventListener.connectionAcquired(call, result);return result;}

上面的源码比较长，加了注释。我们来看看流程图：

a）排除连接不可用的情况；

  private Socket releaseIfNoNewStreams() {assert (Thread.holdsLock(connectionPool));RealConnection allocatedConnection = this.connection;if (allocatedConnection != null && allocatedConnection.noNewStreams) {return deallocate(false, false, true);}return null;}

这个方法是说如果状态处于releaseIfNoNewStreams状态，释放该连接，否则，该连接可用

b）判断连接是否可用

//经过releaseIfNoNewStreams()，如果connection不为null,则连接可用if (this.connection != null) {// We had an already-allocated connection and it's good.//存在可使用的已分配连接，result = this.connection;//为null值，说明这个连接是有效的releasedConnection = null;}

经过releaseIfNoNewStreams（）检查后，Connection不为空则连接可用

c）第一次连接池查找，没有提供路由信息

//通过ConnectionPool,Address,StreamAllocation从连接池中获取连接Internal.instance.get(connectionPool, address, this, null);if (connection != null) {foundPooledConnection = true;result = connection;}

如果找到，则将连接赋值给result

d）遍历路由器进行二次查找

 //提供更加全面的路由信息，再次从连接池中获取连接List<Route> routes = routeSelection.getAll();for (int i = 0, size = routes.size(); i < size; i++) {Route route = routes.get(i);Internal.instance.get(connectionPool, address, this, route);if (connection != null) {foundPooledConnection = true;result = connection;this.route = route;break;}}

e）如果还是没有找到，则只能创建新的连接了

 result = new RealConnection(connectionPool, selectedRoute);acquire(result, false);//添加Connection的StreamAllocation添加到connection.allocations集合中

f）新的连接，连接服务器

 // Do TCP + TLS handshakes. This is a blocking operation.连接serverresult.connect(connectTimeout, readTimeout, writeTimeout, connectionRetryEnabled, call, eventListener);routeDatabase().connected(result.route());//将路由信息添加到routeDatabase中

g）新的连接放入线程池

 // Pool the connection.Internal.instance.put(connectionPool, result);//将新生成的连接放入连接池中

h）如果连接是一个HTTP2连接，则需要确保多路复用的特性

     //如果是HTTP2连接，由于HTTP2连接具有多路复用特性//因此，我们需要确保http2的多路复用特性if (result.isMultiplexed()) {//确保http2的多路复用特性，重复的连接将 被踢除socket = Internal.instance.deduplicate(connectionPool, address, this);result = connection;}

在Connectinterceptor中起到关键作用的就是ConnectionPool，我们来看看ConnectionPool连接池的源码：

在目前版本，连接池是默认保持5个空闲连接的，这些空闲连接如果超过五分钟不被使用，则会被连接池移除，这个两个数值以后可能会改变，同时也是可以自定义修改的

RouteDatabase：路由记录表，这是一个关于路由信息的白名单和黑名单类，处于黑名单的路由信息会被避免不必要的尝试；
Deque:队列，存放待复用的连接
ThreadPoolExecutor:线程池，用于支持线程池的clearup任务，清除idel线程

对于连接池我们联想到的是，存、去、清除：

1）存

  void put(RealConnection connection) {assert (Thread.holdsLock(this));if (!cleanupRunning) {cleanupRunning = true;executor.execute(cleanupRunnable);}connections.add(connection);}

可以看到，在存入连接池connections.add(connection)之前，可能需要执行连接池的清洁任务，连接存入连接池的操作很简单，主要看一下clearup做了什么：

  long cleanup(long now) {int inUseConnectionCount = 0;int idleConnectionCount = 0;RealConnection longestIdleConnection = null;long longestIdleDurationNs = Long.MIN_VALUE;// Find either a connection to evict, or the time that the next eviction is due.synchronized (this) {for (Iterator<RealConnection> i = connections.iterator(); i.hasNext(); ) {RealConnection connection = i.next();// If the connection is in use, keep searching.if (pruneAndGetAllocationCount(connection, now) > 0) {inUseConnectionCount++;//连接池中处于使用状态的连接数continue;}idleConnectionCount++;//处于空闲状态的连接数// If the connection is ready to be evicted, we're done.long idleDurationNs = now - connection.idleAtNanos;//寻找空闲最久的那个连接if (idleDurationNs > longestIdleDurationNs) {longestIdleDurationNs = idleDurationNs;longestIdleConnection = connection;}}//空闲最久的那个连接//如果空闲连接大于keepAliveDurationNs默认五分钟//如果空闲连接数大于maxIdleConnections默认五个//则执行移除操作if (longestIdleDurationNs >= this.keepAliveDurationNs|| idleConnectionCount > this.maxIdleConnections) {// We've found a connection to evict. Remove it from the list, then close it below (outside// of the synchronized block).connections.remove(longestIdleConnection);} else if (idleConnectionCount > 0) {// A connection will be ready to evict soon.return keepAliveDurationNs - longestIdleDurationNs;} else if (inUseConnectionCount > 0) {// All connections are in use. It'll be at least the keep alive duration 'til we run again.return keepAliveDurationNs;} else {// No connections, idle or in use.cleanupRunning = false;return -1;}}closeQuietly(longestIdleConnection.socket());//关闭socket// Cleanup again immediately.return 0;}

这个方法根据两个指标判断是否移除空闲时间最长的连接，大于空闲值或者连接数超过最大值，则移除空闲时间最长的空闲连接，clearup方法的执行也依赖与另一个比较重要的方法：pruneAndGetAllocationCount(connection, now)该方法的作用是移除发生泄漏的StreamAllocation，统计连接中正在使用的StreamAllocation个数。

2）取

  @Nullable RealConnection get(Address address, StreamAllocation streamAllocation, Route route) {assert (Thread.holdsLock(this));for (RealConnection connection : connections) {//isEligible是判断一个连接是否还能携带一个StreamAllocation，如果能则说明这个连接可用if (connection.isEligible(address, route)) {//将StreamAllocation添加到connection.allocations中streamAllocation.acquire(connection, true);return connection;}}return null;}

首先，判断Address对应的Connection是否还能承载一个新的StreamAllocation，可以的话我们将这个StreamAllocation添加到connection.allocations中，最后返回这个Connection。

3）移除

 public void evictAll() {List<RealConnection> evictedConnections = new ArrayList<>();synchronized (this) {for (Iterator<RealConnection> i = connections.iterator(); i.hasNext(); ) {RealConnection connection = i.next();if (connection.allocations.isEmpty()) {connection.noNewStreams = true;evictedConnections.add(connection);i.remove();}}}for (RealConnection connection : evictedConnections) {closeQuietly(connection.socket());}}

关闭并移除连接池中的空闲连接。

（11）CallServerInterceptor

拦截器链最后的拦截器，使用HttpCodec完成最后的请求发送。

三、总结

okhttp是一个http+http2的客户端，使用android+java的应用，整体分析完之后，再来看下面这个框架架构图就清晰很多了

点关注，不迷路

好了各位，以上就是这篇文章的全部内容了，能看到这里的人呀，都是人才。

我是suming，感谢各位的支持和认可，您的点赞、评论、收藏【一键三连】就是我创作的最大动力，我们下篇文章见！

如果本篇博客有任何错误，请批评指教，不胜感激！

要想成为一个优秀的安卓开发者，这里有必须要掌握的知识架构，一步一步朝着自己的梦想前进！Keep Moving!

相关文章：

Retrofit2详解和使用（一）

Retrofit2的介绍和简单使用

OKHttp3的使用和详解

OKHttp3的用法介绍和解析

OKHttp3源码详解

从源码角度解释OKHttp3的关键流程和重要操作

RxJava2详解（一）

详细介绍了RxJava的使用（基本创建、快速创建、延迟创建等操作符）

RxJava2详解（二）

RxJava转换、组合、合并等操作符的使用

RxJava2详解（三）

RxJava延迟、do相关、错误处理等操作符的使用

RxJava2详解（四）

RxJava过滤、其他操作符的使用

上述几篇都是android开发必须掌握的，后续会完善其他部分！

OkHttp3源码详解相关推荐

OkHttp3源码详解(三) 拦截器-RetryAndFollowUpInterceptor
最大恢复追逐次数: private static final int MAX_FOLLOW_UPS = 20; 处理的业务: 实例化StreamAllocation,初始化一个Socket连接对象,获 ...
OkHttp3源码详解(五) okhttp连接池复用机制
1.概述提高网络性能优化,很重要的一点就是降低延迟和提升响应速度. 通常我们在浏览器中发起请求的时候header部分往往是这样的 keep-alive 就是浏览器和服务端之间保持长连接,这个连接是可 ...
okhttp3 请求html页面,OkHttp3源码详解(二) 整体流程
1.简单使用同步:@Override public Response execute() throws IOException { synchronized (this) { if (execute ...
【Live555】live555源码详解（九）：ServerMediaSession、ServerMediaSubsession、live555MediaServer
[Live555]live555源码详解系列笔记继承协作关系图下面红色表示本博客将要介绍的三个类所在的位置: ServerMediaSession.ServerMediaSubsession.Dy ...
【Live555】live555源码详解系列笔记
[Live555]liveMedia下载.配置.编译.安装.基本概念 [Live555]live555源码详解(一):BasicUsageEnvironment.UsageEnvironment [L ...
【Live555】live555源码详解（八）：testRTSPClient
[Live555]live555源码详解系列笔记继承协作关系图下面红色表示本博客将要介绍的testRTSPClient实现的三个类所在的位置: ourRTSPClient.StreamClient ...
【Live555】live555源码详解（七）：GenericMediaServer、RTSPServer、RTSPClient
[Live555]live555源码详解系列笔记继承协作关系图下面红色表示本博客将要介绍的三个类所在的位置: GenericMediaServer.RTSPServer.RTSPClient 14 ...
【Live555】live555源码详解（六）：FramedSource、RTPSource、RTPSink
[Live555]live555源码详解系列笔记继承协作关系图下面红色表示本博客将要介绍的三个类所在的位置: FramedSource.RTPSource.RTPSink 11.FramedSou ...
【Live555】live555源码详解（五）：MediaSource、MediaSink、MediaSession、MediaSubsession
[Live555]live555源码详解系列笔记继承协作关系图下面红色表示本博客将要介绍的四个类所在的位置: MediaSource.MediaSink.MediaSession.MediaSub ...

OkHttp3源码详解