前言

把大象放到冰箱里面,一共需要几步。

  1. 打开冰箱门
  2. 把大象放进去
  3. 关上冰箱门

其实 OkHttp 请求也很简单

  1. 装配Request(涉及到了请求方法, url , cookie 请求)
  2. Client 端发送 Request 请求
  3. 接收服务端返回的 Response 数据

so easy

OkHttp 的使用请参考 扫盲系列 - OkHttp 基本用法

以下是 OKHTTP 一个常见异步用法实例

OkHttpClient okHttpClient = new OkHttpClient();//创建 OkHttpClient 对象
Request request = new Request.Builder()//
    .url("http://www.baidu.com")//请求接口,如果需要传递参数,拼接到后面
    .build();//创建 Request 对象
    //发送 Request 请求
okHttpClient.newCall(request).enqueue(new Callback() {

    @Override
    public void onFailure(Call call, IOException e) {
    }
    //接收返回的 Response 数据
    @Override
    public void onResponse(Call call, Response response) throws IOException {
        if (response.isSuccessful()) {//请求成功
            Log.e("hoyouly", "onResponse currentThread: " + Thread.currentThread() //
                + " \n code: " + response.code() //
                + " \n body: " + response.body().string()//
                + " \n message: " + response.message());
        }
    }
});
  1. 创建 OkHttpClient 对象 这个相当于弄一个冰箱
  2. 创建 Request 请求 打开冰箱门
  3. 发送 Request 放入大象
  4. 接收 Response 关闭冰箱门

这比把大象放入冰箱多了一步,就是找冰箱的过程。整体的流程图如下

接下来就一步一步说

创建 OkHttpClient 对象

这个就没啥好说的,可以通过直接 new 一个 OkHttpClient ,也可以通过OkHttpClient.Builder build()一个,建造者模式嘛。


public OkHttpClient() {
  this(new Builder());
}

public Builder() {
   dispatcher = new Dispatcher();//分发器
   protocols = DEFAULT_PROTOCOLS;//协议
   connectionSpecs = DEFAULT_CONNECTION_SPECS;//传输层版本和连接协议
   eventListenerFactory = EventListener.factory(EventListener.NONE);
   proxySelector = ProxySelector.getDefault();//代理选择
   if (proxySelector == null) {
     proxySelector = new NullProxySelector();
   }
   cookieJar = CookieJar.NO_COOKIES;//cookie
   socketFactory = SocketFactory.getDefault();//socket 工厂
   hostnameVerifier = OkHostnameVerifier.INSTANCE;//  主机名字确认
   certificatePinner = CertificatePinner.DEFAULT;//  证书链
   proxyAuthenticator = Authenticator.NONE;//代理身份验证
   authenticator = Authenticator.NONE;// 本地身份验证
   connectionPool = new ConnectionPool(); //连接池,复用连接
   dns = Dns.SYSTEM;//域名
   followSslRedirects = true;//安全套接层重定向
   followRedirects = true; //本地重定向
   retryOnConnectionFailure = true;//重试连接失败
   callTimeout = 0;
   connectTimeout = 10_000;//连接超时
   readTimeout = 10_000;//read 超时
   writeTimeout = 10_000;//write 超时
   pingInterval = 0;
  }

这些都是默认的,几乎都和 OkHttp 有关。可以通过 build 模式进行修改。如下就是对 OkHttp 的一些修改接口

OkHttpClient 创建完成。接下来就是创建 Request 对象

创建 Request 对象。

这个和 OkhttpClient 差不多的,同样是通过 Build 模式,创建一个 Request ,里面设置了 URL ,还可以设置其他一些属性的,例如 这个就不多讲了, 接下来就看发送Request

newCall

在发送 Request 之前,需要有一个创建一个 Call 对象,使用这个 Call 对象来发送 Request , 所以可以看到 newCall() 中先创建了一个 Call 对象,即 RealCall ,它包装了 Request 和 OKHttpClient 这两个类的实例。这点很重要

//OkHttpClient.java
@Override public Call newCall(Request request) {
   return RealCall.newRealCall(this, request , false /* for web socket */);
 }

//RealCall.java
 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;
 }

RealCall 实现了 Call 这个接口,大部分的操作都在这个 Call ,这个接口是 OkHttp 框架的操作核心。


public interface Call extends Cloneable {
  Request request();
  Response execute() throws IOException;
  void enqueue(Callback responseCallback);
  void cancel();
  boolean isExecuted();
  interface Factory {
    Call newCall(Request request);
  }
}

接下来就是异步执行了 enqueue() ,用来发送 Request 。

发送Request

异步请求enqueue().

@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));
}

client.dispatcher() 就是 Dispatcher ,它是一个分发器,它持有线程池,异步任务队列和同步任务队列,会依照不同的策略执行。

Dispatcher

中有三个队列,等待异步执行的队列

/** Ready async calls in the order they'll be run. */
 private final Deque<AsyncCall> readyAsyncCalls = new ArrayDeque<>();

 /** Running asynchronous calls. Includes canceled calls that haven't finished yet. */
 private final Deque<AsyncCall> runningAsyncCalls = new ArrayDeque<>();

 /** Running synchronous calls. Includes canceled calls that haven't finished yet. */
 private final Deque<RealCall> runningSyncCalls = new ArrayDeque<>();

接下来继续 看 enqueue()

//Dispatcher.java
void enqueue(AsyncCall call) {
    synchronized (this) {
      readyAsyncCalls.add(call);
    }
    promoteAndExecute();
  }

private boolean promoteAndExecute() {
    assert (!Thread.holdsLock(this));

    List<AsyncCall> executableCalls = new ArrayList<>();
    boolean isRunning;
    synchronized (this) {
      for (Iterator<AsyncCall> i = readyAsyncCalls.iterator(); i.hasNext(); ) {
        AsyncCall asyncCall = i.next();

        if (runningAsyncCalls.size() >= maxRequests) break; // Max capacity.
        if (runningCallsForHost(asyncCall) >= maxRequestsPerHost) continue; // Host max capacity.

        i.remove();
        executableCalls.add(asyncCall);
        runningAsyncCalls.add(asyncCall);
      }
      isRunning = runningCallsCount() > 0;
    }

    for (int i = 0, size = executableCalls.size(); i < size; i++) {
      AsyncCall asyncCall = executableCalls.get(i);
      asyncCall.executeOn(executorService());
    }
    return isRunning;
  }


public synchronized ExecutorService executorService() {
    if (executorService == null) {
      executorService = new ThreadPoolExecutor(0, Integer.MAX_VALUE, 60 , TimeUnit.SECONDS,
          new SynchronousQueue<Runnable>(), Util.threadFactory("OkHttp Dispatcher", false));
    }
    return executorService;
  }

AsyncCall 是 RealCall 的一个内部类,持有 RealCall 的引用,是对 RealCall 进行了封装

ExecutorService 是一个核心线程数为 0 的线程池,其实就是 一个 CachedTheadPool 类型的线程池,关于线程池的知识,可以查看 Android 线程池

在 Dispatcher 中会根据情况,把 Call 加入请求队列还是等待队列,在请求队列中,就会在线程池中执行这个请求。

//AsyncCall.java
void executeOn(ExecutorService executorService) {
    assert (!Thread.holdsLock(client.dispatcher()));
    boolean success = false;
    try {
      executorService.execute(this);
      success = true;
    } catch (RejectedExecutionException e) {
      InterruptedIOException ioException = new InterruptedIOException("executor rejected");
      ioException.initCause(e);
      eventListener.callFailed(RealCall.this, ioException);
      responseCallback.onFailure(RealCall.this, ioException);
    } finally {
      if (!success) {
        client.dispatcher().finished(this); // This call is no longer running!
      }
    }
  }

因为 AsyncCall extends NamedRunnable , NamedRunnable 实现了 Runnable ,所以就可以直接查看 run() 方法了。

//,NamedRunnable.java
@Override public final void run() {
  String oldName = Thread.currentThread().getName();
  Thread.currentThread().setName(name);
  try {
    execute();
  } finally {
    Thread.currentThread().setName(oldName);
  }
}

最终执行到了 AsyncCall 的 execute() 方法

@Override protected void execute() {
  boolean signalledCallback = false;
  timeout.enter();
  try {
    Response response = getResponseWithInterceptorChain();
    if (retryAndFollowUpInterceptor.isCanceled()) {
      signalledCallback = true;
      responseCallback.onFailure(RealCall.this, new IOException("Canceled"));
    } else {
      signalledCallback = true;
      responseCallback.onResponse(RealCall.this, response);
    }
  } catch (IOException e) {
    e = timeoutExit(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);
  }
}

感觉已经很靠近了,因为我们看到了 onResponse()/onFailure() 这两个方法, 这个 responseCallback 就是在 enqueue() 中传递过来的 Callback responseCallback ,

那么请求网络的地方,就是 getResponseWithInterceptorChain() 这个了,

Response getResponseWithInterceptorChain() throws IOException {
  // Build a full stack of interceptors.
  List<Interceptor> interceptors = new ArrayList<>();
  //添加开发者应用层自定义的Interceptor
  interceptors.addAll(client.interceptors());
  //这个 Interceptor 是处理请求失败的重试,重定向
  interceptors.add(retryAndFollowUpInterceptor);
  //这个 Interceptor 工作是添加一些请求的头部或其他信息
  //并对返回的 Response 做一些友好的处理(有一些信息你可能并不需要)
  interceptors.add(new BridgeInterceptor(client.cookieJar()));
  //这个 Interceptor 的职责是判断缓存是否存在,读取缓存,更新缓存等等
  interceptors.add(new CacheInterceptor(client.internalCache()));
  //这个 Interceptor 的职责是建立客户端和服务器的连接
  interceptors.add(new ConnectInterceptor(client));
  if (!forWebSocket) {
    //添加开发者自定义的网络层拦截器
    interceptors.addAll(client.networkInterceptors());
  }
  //这个 Interceptor 的职责是向服务器发送数据,并且接收服务器返回的Response
  interceptors.add(new CallServerInterceptor(forWebSocket));
  //一个包裹这 request 的chain
  Interceptor.Chain chain = new RealInterceptorChain(interceptors, null , null , null , 0 ,
 originalRequest , this , eventListener , client.connectTimeoutMillis(),
      client.readTimeoutMillis(), client.writeTimeoutMillis());
  //把 chain 传递到第一个 Interceptor 手中
  return chain.proceed(originalRequest);
}
  1. Interceptor 的执行是有顺序的。也就意味这当我们自定义 Interceptor 是需要注意添加顺序
  2. 在开发者自定义的 Interceptor ,是有两种不同的拦截器可以自定义的。

拦截器

使用责任链模式模式,添加了各种 interceptors ,然后执行了 RealInterceptorChain 的 proceed()

//RealInterceptorChain.java
@Override public Response proceed(Request request) throws IOException {
    return proceed(request, streamAllocation , httpCodec , connection);
  }
  //这个方法用来获取 list 中下一个 Interceptor ,并调用它的intercept()方法

public Response proceed(Request request, StreamAllocation streamAllocation , HttpCodec httpCodec ,
      RealConnection connection) throws IOException {
    if (index >= interceptors.size()) throw new AssertionError();

    calls++;

    //如果我们已经有一个 stream 。确定即将到来的 request 会使用它
    if (this.httpCodec != null && !this.connection.supportsUrl(request.url())) {
      throw new IllegalStateException("network interceptor " + interceptors.get(index - 1) + " must retain the same host and port");
    }

  //如果我们已经有一个 stream , 确定chain.proceed()唯一的call
    if (this.httpCodec != null && calls > 1) {
      throw new IllegalStateException("network interceptor " + interceptors.get(index - 1)+ " must call proceed() exactly once");
    }

    // Call the next interceptor in the chain.取出来下一个拦截器,然后执行 intercept()
    RealInterceptorChain next = new RealInterceptorChain(interceptors, streamAllocation , httpCodec ,
 connection , index + 1, request , call , eventListener , connectTimeout , readTimeout , writeTimeout);
  //从 list 中获取到第一个Interceptor
    Interceptor interceptor = interceptors.get(index);
    Response response = interceptor.intercept(next);

    // Confirm that the next interceptor made its required call to chain.proceed().
    if (httpCodec != null && index + 1 < interceptors.size() && next.calls != 1) {
      throw new IllegalStateException("network interceptor " + interceptor + " must call proceed() exactly once");
    }

    // Confirm that the intercepted response isn't null.
    if (response == null) {
      throw new NullPointerException("interceptor " + interceptor + " returned null");
    }

    if (response.body() == null) {
      throw new IllegalStateException( "interceptor " + interceptor + " returned a response with no body");
    }

    return response;
  }

这个有点像是递归调用。

关键代码是

// 实例化下一个拦截器对应的 RealIterceptorChain 对象, index 刚开始是 0 ,这里加一,下次取的时候就是下一个 interceptors
RealInterceptorChain next = new RealInterceptorChain(interceptors, streamAllocation , httpCodec ,
 connection , index + 1, request , call , eventListener , connectTimeout , readTimeout ,
    writeTimeout);
//得到当前的拦截器:
Interceptor interceptor = interceptors.get(index);
//调用当前拦截器的 intercept() 方法,并将下一个拦截器的 RealIterceptorChain 对象传递下去
Response response = interceptor.intercept(next);
  1. 实例化下一个拦截器对应的 RealIterceptorChain 对象,这个对象会再传递给当前的拦截器
  2. 得到当前的拦截器:interceptors是存放拦截器的ArryList
  3. 调用当前拦截器的 intercept() 方法,并将下一个拦截器的 RealIterceptorChain 对象传递下去
  4. 在下一个 Interceptor 的 intercept() 中,会执行 chain.proceed(request),这样就进入到下次循环中了

这也是为啥,我们自定义的 Interceptor ,在 intercept() 中,都会执行 chain.proceed(request) 这行代码的缘故 如果不执行这行代码,那么责任链模式就没办法进行了。 说到这里,就可以解释一下 addInterceptor() 和 addNetworkInterceptor() 区别了

addInterceptor()和 addNetworkInterceptor() 区别

addInterceptor() 添加应用拦截器

  • 不需要担心中间过程的响应,如重定向和重试
  • 总是只调用一次,即便是 HTTP 从缓存中获取
  • 观察应用程序的初衷,不关心 Okhttp 注入信息的头信息,如If-NONE-Match
  • 允许短路而不调用Chain.proceed(),即终止调用
  • 允许重试,试Chain.proceed()调用多次 addNetworkInterceptor() 添加网络拦截器
  • 能够操作中间过程的响应,如重定向和重试
  • 当网络短路而返回缓存的时候不调用
  • 只观察在网络传输中的数据
  • 携带请求来访问连接

注意,如果添加的 addInterceptor() 中不执行 chain.proceed(request) ,那么就不会执行到下面的 网络重试,以及最关键的 CallServerInterceptor 这个 Interceptor 了。

一个 Interceptor 集合,从第一个开始,然后执行 intercept() 的方法,里面会创建 RealInterceptorChain ,然后执行下一个 proceed() 方法,就这样一直到了最后一个, 也就是 CallServerInterceptor 中,

除了 在 client 中自己设置的 interceptor ,第一个调用的就是retryAndFollowUpInterceptor

RetryAndFollowUpInterceptor

负责失败重试以及重定向

@Override public Response intercept(Chain chain) throws IOException {
    Request request = chain.request();
    RealInterceptorChain realChain = (RealInterceptorChain) chain;
    ...
    Response priorResponse = null;
    while (true) {
      ...
      try {
        response = realChain.proceed(request, streamAllocation , null , null);
        releaseConnection = false;
      } catch (RouteException e) {
        ...
      }
      // Attach the prior response if it exists. Such responses never have a body.
      if (priorResponse != null) {
        response = response.newBuilder().priorResponse(priorResponse.newBuilder().body(null).build()).build();
      }
      ...
      priorResponse = response;
    }
  }

看到没有,这里面也执行了 realChain.proceed(),所以会传递到下一个拦截器中,即 BridgeInterceptor

BridgeInterceptor

负责把用户构造的请求转换为发送到服务器的请求、把服务器返回的响应转换为用户友好的响应的

@Override public Response intercept(Chain chain) throws IOException {
    Request userRequest = chain.request();
    Request.Builder requestBuilder = userRequest.newBuilder();
    //检查 request 。将用户的 request 转换为发送到 server 的请求
    RequestBody body = userRequest.body();
    ...
    Response networkResponse = chain.proceed(requestBuilder.build());

    HttpHeaders.receiveHeaders(cookieJar, userRequest.url(), networkResponse.headers());

    Response.Builder responseBuilder = networkResponse.newBuilder().request(userRequest);
    ...
    return responseBuilder.build();
  }

同样执行了 chain.proceed(),那么就可以继续传递拦截器。即 CacheInterceptor

CacheInterceptor

缓存拦截器


@Override public Response intercept(Chain chain) throws IOException {
    Response cacheCandidate = cache != null ? cache.get(chain.request()) : null;

    long now = System.currentTimeMillis();

    CacheStrategy strategy = new CacheStrategy.Factory(now, chain.request(), cacheCandidate).get();
    Request networkRequest = strategy.networkRequest;
    Response cacheResponse = strategy.cacheResponse;

    if (cache != null) {
      cache.trackResponse(strategy);
    }

    if (cacheCandidate != null && cacheResponse == null) {
      closeQuietly(cacheCandidate.body()); // The cache candidate wasn't applicable. Close it.
    }

    //如果我们禁止使用网络,且缓存为 null ,失败
    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();
    }

    //没有网络请求,跳过网络,返回缓存
    if (networkRequest == null) {
      return cacheResponse.newBuilder()
          .cacheResponse(stripBody(cacheResponse))
          .build();
    }

    Response networkResponse = null;
    try {
      networkResponse = chain.proceed(networkRequest);
    } finally {
      //如果我们因为I/O或其他原因崩溃,不要泄漏缓存体
      if (networkResponse == null && cacheCandidate != null) {
        closeQuietly(cacheCandidate.body());
      }
    }

    //如果我们有一个缓存的 response ,然后我们正在做一个条件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();

      //更新缓存,在剥离content-Encoding之前
        cache.trackConditionalCacheHit();
        cache.update(cacheResponse, response);
        return response;
      } else {
        closeQuietly(cacheResponse.body());
      }
    }

    Response response = networkResponse.newBuilder()
        .cacheResponse(stripBody(cacheResponse))
        .networkResponse(stripBody(networkResponse))
        .build();

    if (cache != null) {
      if (HttpHeaders.hasBody(response) && CacheStrategy.isCacheable(response, networkRequest)) {
        // Offer this request to the cache.
        CacheRequest cacheRequest = cache.put(response);
        return cacheWritingResponse(cacheRequest, response);
      }

      if (HttpMethod.invalidatesCache(networkRequest.method())) {
        try {
          cache.remove(networkRequest);
        } catch (IOException ignored) {
          // The cache cannot be written.
        }
      }
    }
    return response;
  }

缓存策略

  1. 根据 request 来判断 cache 中是否有缓存的 response ,如果设置了缓存,即 在OkHttpClient.Builder 中 执行了 cache() ,那么 cache 就不为 null ,
  2. 如果有,得到这个 response ,然后进行判断当前 response 是否有效,没有将 cacheCandate 赋值为空
  3. 根据 request 判断缓存的策略,是否要使用了网络,缓存 或两者都使用
  4. 调用下一个拦截器,决定从网络上来得到response
  5. 如果本地已经存在 cacheResponse ,那么让它和网络得到的 networkResponse 做比较,决定是否来更新缓存的cacheResponse
  6. 缓存未经缓存过的response

同样也是执行了 chain.proceed(networkRequest),继续传递下一个,即 ConnectInterceptor

ConnectInterceptor

建立连接

@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.
  boolean doExtensiveHealthChecks = !request.method().equals("GET");
  HttpCodec httpCodec = streamAllocation.newStream(client, chain , doExtensiveHealthChecks);
  RealConnection connection = streamAllocation.connection();

  return realChain.proceed(request, streamAllocation , httpCodec , connection);
}

其实就是创建了一个 HttpCodec 对象。 是对 HTTP 协议的一种抽象,有两个实现:Http1Codec和 Http2Codec ,顾名思义,它们分别对应 HTTP/1.1 和 HTTP/2 版本的实现 也执行了 realChain.proceed(),那么继续,如果不是 webSocket ,那么就是 NetworkInterceptors

NetworkInterceptors

配置 OkHttpClient 时设置的 NetworkInterceptors 。这里面一般也会执行的,如果不执行realChain.proceed(),那么就执行不到下一步了,即 CallServerInterceptor ,真正的发送和接收数据

CallServerInterceptor

发送和接收数据

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

  long sentRequestMillis = System.currentTimeMillis();

  realChain.eventListener().requestHeadersStart(realChain.call());
  httpCodec.writeRequestHeaders(request);
  realChain.eventListener().requestHeadersEnd(realChain.call(), request);

  Response.Builder responseBuilder = null;
  if (HttpMethod.permitsRequestBody(request.method()) && request.body() != null) {
    if ("100-continue".equalsIgnoreCase(request.header("Expect"))) {
      httpCodec.flushRequest();
      realChain.eventListener().responseHeadersStart(realChain.call());
      responseBuilder = httpCodec.readResponseHeaders(true);
    }

    if (responseBuilder == null) {
      // Write the request body if the "Expect: 100-continue" expectation was met.
      realChain.eventListener().requestBodyStart(realChain.call());
      long contentLength = request.body().contentLength();
      CountingSink requestBodyOut =
          new CountingSink(httpCodec.createRequestBody(request, contentLength));
      BufferedSink bufferedRequestBody = Okio.buffer(requestBodyOut);

      request.body().writeTo(bufferedRequestBody);
      bufferedRequestBody.close();
      realChain.eventListener()
          .requestBodyEnd(realChain.call(), requestBodyOut.successfulCount);
    } else if (!connection.isMultiplexed()) {
      streamAllocation.noNewStreams();
    }
  }

  httpCodec.finishRequest();

  if (responseBuilder == null) {
    realChain.eventListener().responseHeadersStart(realChain.call());
    responseBuilder = httpCodec.readResponseHeaders(false);
  }

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

  int code = response.code();
  if (code == 100) {
    // server sent a 100-continue even though we did not request one.
    // try again to read the actual response
    responseBuilder = httpCodec.readResponseHeaders(false);

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

    code = response.code();
  }

  realChain.eventListener().responseHeadersEnd(realChain.call(), response);

  if (forWebSocket && code == 101) {
    // Connection is upgrading, but we need to ensure interceptors see a non-null response body.
    response = response.newBuilder()
        .body(Util.EMPTY_RESPONSE)
        .build();
  } else {
    response = response.newBuilder()
        .body(httpCodec.openResponseBody(response))
        .build();
  }

  if ("close".equalsIgnoreCase(response.request().header("Connection"))
      || "close".equalsIgnoreCase(response.header("Connection"))) {
    streamAllocation.noNewStreams();
  }

  if ((code == 204 || code == 205) && response.body().contentLength() > 0) {
    throw new ProtocolException(
        "HTTP " + code + " had non-zero Content-Length: " + response.body().contentLength());
  }

  return response;
}

这里面没有执行 chain.proceed(request),所以责任链到此结束,在这个 Intercept 中,真正得到网络数据,然后再通过 chain.proceed(request)一级一级返回 response ,最后到 RealCall 的 getResponseWithInterceptorChain() 中,这样就能继续执行下面的操作了,即返回这个 result ,还是执行callFailed().


搬运地址:

从 OKHttp 框架看代码设计

OKHttp源码解析

OkHttp中的 Socket 连接

Andriod 网络框架 OkHttp 源码解析

Retrofit使用 addInterceptor 和 addNetworkInterceptor 的区别