OkHttpClient的工作

• 建造者模式创建实例本身
• 通信的客户端，用来统一管理发起请求与解析响应。
• 实例化Dispatcher 请求任务调度器，将会单独开篇讲述
• 实例化 ConnectionPool连接池，用来管理和复用连接，将会单独开篇讲述

源码分析

1. 内部类Builder源码分析

new OkHttpClient.Builder()

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

这里在初始化的时候做了一些数据初始化操作，需要特别注意的是初始化的时候就实例化了任务调度器Dispatcher和连接池ConnectionPool。

常用的方法介绍

Builder().connectTimeout(): 连接超时时长设置

    public Builder connectTimeout(long timeout, TimeUnit unit) {
      connectTimeout = checkDuration("timeout", timeout, unit);
      return this;
    }

Builder().readTimeout(): 读取超时时长设置

    public Builder readTimeout(long timeout, TimeUnit unit) {
      readTimeout = checkDuration("timeout", timeout, unit);
      return this;
    }

Builder().writeTimeout(): 写入超时时长设置

    public Builder writeTimeout(long timeout, TimeUnit unit) {
      writeTimeout = checkDuration("timeout", timeout, unit);
      return this;
    }

Builder().cache(): 缓存设置

    public Builder cache(@Nullable Cache cache) {
      this.cache = cache;
      this.internalCache = null;
      return this;
    }

Builder().build(): 生成OkHttpClient对象方法

    public OkHttpClient build() {
      return new OkHttpClient(this);
    }

2. OkHttpClient方法

newCall(Request): 生成RealCall对象实例

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