OkHttp源码解析（1）

在上一篇博客中，我们介绍了OKHttp的基本用法，这一篇我们将从源码角度来看下OKHttp是如何完成一些列的网络的操作的。 

我们知道在okhttpclient同步请求和异步请求调用的接口不一样，但它们最后都是殊途同归地走到Call里面的

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> Response <span class="hljs-title" style="box-sizing: border-box;">getResponseWithInterceptorChain</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> forWebSocket) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throws</span> IOException {
Call.ApplicationInterceptorChain chain = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Call.ApplicationInterceptorChain(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.originalRequest, forWebSocket);
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> chain.proceed(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.originalRequest);
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul>

首先我们来看看调用execute和enqueue是如何走到`getResponseWithInterceptorChain的。

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> Response <span class="hljs-title" style="box-sizing: border-box;">execute</span>() <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throws</span> IOException {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">synchronized</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>) {
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//执行过不能再执行</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.executed) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throw</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> IllegalStateException(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Already Executed"</span>);
}

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.executed = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>;
}

Response var2;
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">try</span> {
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//把这次请求加入到分发器里</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.client.getDispatcher().executed(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>);
Response result = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.getResponseWithInterceptorChain(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>);
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(result == <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throw</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> IOException(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Canceled"</span>);
}

var2 = result;
} <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">finally</span> {
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.client.getDispatcher().finished(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>);
}

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> var2;
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li></ul>

上面代码14行用到了一个从OkHttpClient获得的Dispatcher然后把它加入到分发器里面的队列 executedCalls中，在完成的时候会remove掉

<code class="hljs sql has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">synchronized void executed(<span class="hljs-operator" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">Call</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">call</span>) {
this.executedCalls.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">add</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">call</span>);</span>
}

synchronized void finished(<span class="hljs-operator" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">Call</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">call</span>) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(!this.executedCalls.remove(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">call</span>)) {
throw new AssertionError(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Call wasn\'t in-flight!"</span>);</span>
}
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li></ul>

再来看看异步如何走到getResponseWithInterceptorChain

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">enqueue</span>(Callback responseCallback) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.enqueue(responseCallback, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>);
}

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> enqueue(Callback responseCallback, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> forWebSocket) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">synchronized</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.executed) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throw</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> IllegalStateException(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Already Executed"</span>);
}

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.executed = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>;
}

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.client.getDispatcher().enqueue(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Call.AsyncCall(responseCallback, forWebSocket, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>));
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li></ul>

是不是和同步很像，最后都是调用分发器的enqueue，但和同步不同的是，同步传入enqueue方法的参数是Call，异步传入的是AsyncCall，这个是什么呢，这个是Call里面的一个内部类，而且是一个继承了Runnable的内部类，我们先来看看这个execute怎么操作

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">synchronized void enqueue(AsyncCall <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">call</span>) {
//判断当前运行的线程是否超过最大线程数，以及同一个请求是否要超过相同请求同时存在的最大数目
if(this<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.runningCalls</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.size</span>() < this<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.maxRequests</span> && this<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.runningCallsForHost</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">call</span>) < this<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.maxRequestsPerHost</span>) {
this<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.runningCalls</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.add</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">call</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
//将请求放到线程池里运行
this<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.getExecutorService</span>()<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.execute</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">call</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
} else {
//不满足运行条件放到后备队列里
this<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.readyCalls</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.add</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">call</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
}

}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li></ul>

从上面代码我们看到异步请求是有条件限制的，默认最多64个请求，而同一个请求默认最多同时存在5个

<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> <span class="hljs-title" style="box-sizing: border-box;">runningCallsForHost</span>(AsyncCall call) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> result = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>;
Iterator var3 = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.runningCalls.iterator();

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">while</span>(var3.hasNext()) {
AsyncCall c = (AsyncCall)var3.next();
通过比较每个请求的url，一样代表同一个请求
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(c.host().equals(call.host())) {
++result;
}
}

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> result;
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li></ul>

下面的两个参数可以通过从OKHttpClient getDispatch得到分发器，并根据分发器提提供的设置方法去修改，修改比较简单就不贴代码了 。

<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> maxRequests = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">64</span>;
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> maxRequestsPerHost = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">5</span>;</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li></ul>

再来看看AsyncCall 的run里面的代码

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">run</span>() {
String oldName = Thread.currentThread().getName();
Thread.currentThread().setName(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.name);

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">try</span> {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.execute();
} <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">finally</span> {
Thread.currentThread().setName(oldName);
}

}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li></ul>

显然AsyncCall的execute才是核心

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">protected void execute() {
boolean signalledCallback = false<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>

try {
Response e = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">Call</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.this</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.getResponseWithInterceptorChain</span>(this<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.forWebSocket</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
if(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">Call</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.this</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.canceled</span>) {
signalledCallback = true<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
//取消<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">call</span>调用onFailure回调                       this<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.responseCallback</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.onFailure</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">Call</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.this</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.originalRequest</span>, new IOException(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Canceled"</span>))<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
} else {
signalledCallback = true<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
//请求成功，回调onResponse
this<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.responseCallback</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.onResponse</span>(e)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
}
} catch (IOException var6) {
if(signalledCallback) {
Internal<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.logger</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.log</span>(Level<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.INFO</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Callback failure for "</span> + <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">Call</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.this</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.toLoggableString</span>(), var6)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
} else {
this<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.responseCallback</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.onFailure</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">Call</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.this</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.engine</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.getRequest</span>(), var6)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
}
} finally {
//完成请求，调用finish，从队列中清空
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">Call</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.this</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.client</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.getDispatcher</span>()<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.finished</span>(this)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
}

}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li></ul>

在代码第五行我们又看到了getResponseWithInterceptorChain。 

我们继续看getResponseWithInterceptorChain里面的实现

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> Response <span class="hljs-title" style="box-sizing: border-box;">getResponseWithInterceptorChain</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> forWebSocket) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throws</span> IOException {
Call.ApplicationInterceptorChain chain = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Call.ApplicationInterceptorChain(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.originalRequest, forWebSocket);
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> chain.proceed(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.originalRequest);
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul>

创建了一个ApplicationInterceptorChain ，并且第一个参数传入0，这个0是有特殊用法的，涉及到OKHttp里面的一个功能叫做拦截器，从getResponseWithInterceptorChain这个名字里其实也能看出一二。先看看proceed做了什么

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">public Response proceed(Request request) throws IOException {
//先判断是否每个拦截器都有对应的处理，没有的话先继续新建ApplicationInterceptorChain ，并执行当前拦截器的intercept方法
if(this<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.index</span> < <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">Call</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.this</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.client</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.interceptors</span>()<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.size</span>()) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">Call</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.ApplicationInterceptorChain</span> chain = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">Call</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.this</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.new</span> ApplicationInterceptorChain(this<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.index</span> + <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>, request, this<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.forWebSocket</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
return ((Interceptor)<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">Call</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.this</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.client</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.interceptors</span>()<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.get</span>(this<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.index</span>))<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.intercept</span>(chain)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
} else {
return <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">Call</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.this</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.getResponse</span>(request, this<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.forWebSocket</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
}
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li></ul>

这里碰到一个拦截器，OKHttp增加了一个拦截器机制，先来看看官方文档对Interceptors 的解释 

Interceptors are a powerful mechanism that can monitor, rewrite, and retry calls. 

解释下就是拦截器可以用来转换，重试，重写请求的机制，再来看看官方文档里提供的例子 

首先自定义一个拦截器用于打印一些发送信息

<code class="hljs axapta has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">LoggingInterceptor</span> <span class="hljs-inheritance" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">implements</span></span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">Interceptor</span> {</span>
@Override <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> Response intercept(Chain chain) throws IOException {
Request request = chain.request();

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">long</span> t1 = System.nanoTime();
logger.info(String.format(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Sending request %s on %s%n%s"</span>,
request.url(), chain.connection(), request.headers()));

Response response = chain.proceed(request);

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">long</span> t2 = System.nanoTime();
logger.info(String.format(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Received response for %s in %.1fms%n%s"</span>,
response.request().url(), (t2 - t1) / <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1e6</span>d, response.headers()));

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> response;
}
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li></ul>

然后使用的时候把它添加到okhttpclient

<code class="hljs vbscript has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">OkHttpClient client = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> OkHttpClient();
client.interceptors().add(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> LoggingInterceptor());

<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">Request</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">request</span> = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">Request</span>.Builder()
.url(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"http://www.publicobject.com/helloworld.txt"</span>)
.header(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"User-Agent"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"OkHttp Example"</span>)
.build();

<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">Response</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">response</span> = client.newCall(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">request</span>).<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">execute</span>();
<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">response</span>.body().close();</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li></ul>

当我们执行到proceed，就会去判断是否有拦截器有的话先执行拦截器里的intercept，而在intercept里一般会进行一些自定义操作并且调用procced去判断是否要继续执行拦截器操作还是直接去获取网络请求，我们看看procced做了什么

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">public Response proceed(Request request) throws IOException {
//判断还有拦截器需要执行不，生成新的ApplicationInterceptorChain并调用它的intercept去执行用户定义的操作
if(this<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.index</span> < <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">Call</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.this</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.client</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.interceptors</span>()<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.size</span>()) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">Call</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.ApplicationInterceptorChain</span> chain = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">Call</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.this</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.new</span> ApplicationInterceptorChain(this<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.index</span> + <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>, request, this<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.forWebSocket</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
return ((Interceptor)<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">Call</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.this</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.client</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.interceptors</span>()<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.get</span>(this<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.index</span>))<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.intercept</span>(chain)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
} else {
return <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">Call</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.this</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.getResponse</span>(request, this<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.forWebSocket</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
}
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li></ul>

上面的例子执行结果如下

<code class="hljs http has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-attribute" style="box-sizing: border-box;">INFO</span>: <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">Sending request http://www.publicobject.com/helloworld.txt on null</span>
<span class="hljs-attribute" style="box-sizing: border-box;">User-Agent</span>: <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">OkHttp Example</span>

<span class="http" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">INFO</span>: <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">Received response for https://publicobject.com/helloworld.txt in 1179.7ms</span>
<span class="hljs-attribute" style="box-sizing: border-box;">Server</span>: <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">nginx/1.4.6 (Ubuntu)</span>
<span class="hljs-attribute" style="box-sizing: border-box;">Content-Type</span>: <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">text/plain</span>
<span class="hljs-attribute" style="box-sizing: border-box;">Content-Length</span>: <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">1759</span>
<span class="hljs-attribute" style="box-sizing: border-box;">Connection</span>: <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">keep-alive</span></span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li></ul>

拦截器的整个机制如下图


上图中把拦截器氛围应用拦截器和网络拦截器，其实这个取决于你在拦截器里做了哪方面的操作，比如改变了请求头部之类的就可以成为网络拦截器。

在处理完拦截器操作后，就进入到重要的getResponse方法，真正的去进行发送请求，处理请求，接收返回结果。

<code class="hljs d has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">Response getResponse(Request request, boolean forWebSocket) throws IOException {
RequestBody <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">body</span> = request.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">body</span>();
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">body</span> != <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">null</span>) {
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//如果是post方式，处理一些头部信息</span>
Builder followUpCount = request.newBuilder();
MediaType response = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">body</span>.contentType();
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(response != <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">null</span>) {
followUpCount.header(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Content-Type"</span>, response.toString());
}

<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">long</span> followUp = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">body</span>.contentLength();
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(followUp != -<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1L</span>) {
followUpCount.header(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Content-Length"</span>, Long.toString(followUp));
followUpCount.removeHeader(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Transfer-Encoding"</span>);
} <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> {
followUpCount.header(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Transfer-Encoding"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"chunked"</span>);
followUpCount.removeHeader(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Content-Length"</span>);
}
request = followUpCount.build();
}
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//新建HttpEngine，用于进行发送请求和读取答复的细节处理</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.engine = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> HttpEngine(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.client, request, <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">false</span>, <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">false</span>, forWebSocket, (Connection)<span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">null</span>, (RouteSelector)<span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">null</span>, (RetryableSink)<span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">null</span>, (Response)<span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">null</span>);
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> var11 = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>;

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">while</span>(!<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.canceled) {
HttpEngine var13;
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">try</span> {
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//发送请求</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.engine.sendRequest();
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//读取答复</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.engine.readResponse();
} <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">catch</span> (RequestException var8) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throw</span> var8.getCause();
} <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">catch</span> (RouteException var9) {
var13 = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.engine.recover(var9);
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(var13 != <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">null</span>) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.engine = var13;
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">continue</span>;
}

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throw</span> var9.getLastConnectException();
} <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">catch</span> (IOException var10) {
var13 = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.engine.recover(var10, (Sink)<span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">null</span>);
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(var13 != <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">null</span>) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.engine = var13;
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">continue</span>;
}

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throw</span> var10;
}

Response var12 = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.engine.getResponse();
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//得到该请求对应的后续请求，比如重定向之类的</span>
Request var14 = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.engine.followUpRequest();
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(var14 == <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">null</span>) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(!forWebSocket) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.engine.releaseConnection();
}

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> var12;
}

++var11;
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(var11 > <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">20</span>) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throw</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ProtocolException(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Too many follow-up requests: "</span> + var11);
}

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(!<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.engine.sameConnection(var14.url())) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.engine.releaseConnection();
}

Connection connection = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.engine.close();
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.engine = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> HttpEngine(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.client, var14, <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">false</span>, <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">false</span>, forWebSocket, connection, (RouteSelector)<span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">null</span>, (RetryableSink)<span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">null</span>, var12);
}

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.engine.releaseConnection();
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throw</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> IOException(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Canceled"</span>);
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li><li style="box-sizing: border-box; padding: 0px 5px;">53</li><li style="box-sizing: border-box; padding: 0px 5px;">54</li><li style="box-sizing: border-box; padding: 0px 5px;">55</li><li style="box-sizing: border-box; padding: 0px 5px;">56</li><li style="box-sizing: border-box; padding: 0px 5px;">57</li><li style="box-sizing: border-box; padding: 0px 5px;">58</li><li style="box-sizing: border-box; padding: 0px 5px;">59</li><li style="box-sizing: border-box; padding: 0px 5px;">60</li><li style="box-sizing: border-box; padding: 0px 5px;">61</li><li style="box-sizing: border-box; padding: 0px 5px;">62</li><li style="box-sizing: border-box; padding: 0px 5px;">63</li><li style="box-sizing: border-box; padding: 0px 5px;">64</li><li style="box-sizing: border-box; padding: 0px 5px;">65</li><li style="box-sizing: border-box; padding: 0px 5px;">66</li><li style="box-sizing: border-box; padding: 0px 5px;">67</li><li style="box-sizing: border-box; padding: 0px 5px;">68</li><li style="box-sizing: border-box; padding: 0px 5px;">69</li><li style="box-sizing: border-box; padding: 0px 5px;">70</li><li style="box-sizing: border-box; padding: 0px 5px;">71</li><li style="box-sizing: border-box; padding: 0px 5px;">72</li><li style="box-sizing: border-box; padding: 0px 5px;">73</li><li style="box-sizing: border-box; padding: 0px 5px;">74</li><li style="box-sizing: border-box; padding: 0px 5px;">75</li><li style="box-sizing: border-box; padding: 0px 5px;">76</li><li style="box-sizing: border-box; padding: 0px 5px;">77</li><li style="box-sizing: border-box; padding: 0px 5px;">78</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li><li style="box-sizing: border-box; padding: 0px 5px;">53</li><li style="box-sizing: border-box; padding: 0px 5px;">54</li><li style="box-sizing: border-box; padding: 0px 5px;">55</li><li style="box-sizing: border-box; padding: 0px 5px;">56</li><li style="box-sizing: border-box; padding: 0px 5px;">57</li><li style="box-sizing: border-box; padding: 0px 5px;">58</li><li style="box-sizing: border-box; padding: 0px 5px;">59</li><li style="box-sizing: border-box; padding: 0px 5px;">60</li><li style="box-sizing: border-box; padding: 0px 5px;">61</li><li style="box-sizing: border-box; padding: 0px 5px;">62</li><li style="box-sizing: border-box; padding: 0px 5px;">63</li><li style="box-sizing: border-box; padding: 0px 5px;">64</li><li style="box-sizing: border-box; padding: 0px 5px;">65</li><li style="box-sizing: border-box; padding: 0px 5px;">66</li><li style="box-sizing: border-box; padding: 0px 5px;">67</li><li style="box-sizing: border-box; padding: 0px 5px;">68</li><li style="box-sizing: border-box; padding: 0px 5px;">69</li><li style="box-sizing: border-box; padding: 0px 5px;">70</li><li style="box-sizing: border-box; padding: 0px 5px;">71</li><li style="box-sizing: border-box; padding: 0px 5px;">72</li><li style="box-sizing: border-box; padding: 0px 5px;">73</li><li style="box-sizing: border-box; padding: 0px 5px;">74</li><li style="box-sizing: border-box; padding: 0px 5px;">75</li><li style="box-sizing: border-box; padding: 0px 5px;">76</li><li style="box-sizing: border-box; padding: 0px 5px;">77</li><li style="box-sizing: border-box; padding: 0px 5px;">78</li></ul>

可以看到如果是post请求，先做一定的头部处理，然后新建一个HttpEngine去处理具体的操作，通过sendRequest发送具体请求操作，readResponse对服务器的答复做一定处理，在代码52行处getResponse得到从服务器返回的Response，讲到这里，我们整个的流程大概疏通了，代码贴了很多，简单的可以用下面一张图概括 



整体看就是根据用户的请求Request放入到指定队列，并使用拦截器链的方式去执行我们的请求操作。 

上图中的sendRequest，缓存处理，readReponse，介于篇幅问题（本来想一篇写完的，结果发现篇幅好长，分几篇完成吧）将在后续的文章中继续介绍。