android OkHttp3

请求/响应流程序分析

1、详解创建OkHttpClient

OkHttpClient mOkHttpClient = new OkHttpClient();

其主要调用

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

这里通过静态内部类Builder实现OkHttpClient的构建

public Builder() {        //每一个Dispatcher都有一个线程池，用来分发异步请求      dispatcher = new Dispatcher();        //支持的协议，Http1.1 Http2.0      protocols = DEFAULT_PROTOCOLS;      connectionSpecs = DEFAULT_CONNECTION_SPECS;      eventListenerFactory = EventListener.factory(EventListener.NONE);      proxySelector = ProxySelector.getDefault();      cookieJar = CookieJar.NO_COOKIES;      socketFactory = SocketFactory.getDefault();      hostnameVerifier = OkHostnameVerifier.INSTANCE;      certificatePinner = CertificatePinner.DEFAULT;      proxyAuthenticator = Authenticator.NONE;      authenticator = Authenticator.NONE;      connectionPool = new ConnectionPool();      dns = Dns.SYSTEM;      followSslRedirects = true;      followRedirects = true;      retryOnConnectionFailure = true;      connectTimeout = 10_000;      readTimeout = 10_000;      writeTimeout = 10_000;      pingInterval = 0;    }

2、详解创建Request类实例

这个类其实作用很简单，就是代表一个HTTP请求

Request request = new Request.Builder()                .url("http://112.4.3.136:8080/portalone/homesdk/NetTVUniLogin")                .addHeader("name", "test")                .build();

其中Builder为Request的内部类

3、详解OkHttpClient实例调用newCall方法，返回Call

Call call = mOkHttpClient.newCall(request);

Call是一个接口，RealCall实现了这个接口，当调用newCall方法传入request参数的时候，实际上是返回一个RealCall。

4、详解Call的enqueue方法，将待执行请求放入到线程池

call.enqueue(new Callback() {            @Override            public void onFailure(Call call, IOException e) {            }            @Override            public void onResponse(Call call, Response response) throws IOException {            }        });

我们看下RealCall enqueue方法，

 @Override public void enqueue(Callback responseCallback) {    synchronized (this) {        //如果一个请求正在被执行，则抛出异常      if (executed) throw new IllegalStateException("Already Executed");      executed = true;    }    captureCallStackTrace();    eventListener.callStart(this);    client.dispatcher().enqueue(new AsyncCall(responseCallback));  }

AsyncCall是什么？

AsyncCall继承自NamedRunnable，NamedRunnable实现了Runnable接口

public abstract class NamedRunnable implements Runnable {  protected final String name;  public NamedRunnable(String format, Object... args) {    this.name = Util.format(format, args);  }  @Override public final void run() {    String oldName = Thread.currentThread().getName();    Thread.currentThread().setName(name);    try {      execute();    } finally {      Thread.currentThread().setName(oldName);    }  }  protected abstract void execute();}

NamedRunnable每次执行的时候，都会调用抽象方法execute，则必然其子类在run的时候，execute也会被执行。最后会调用

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

到这里我们也得到几个新的知识点：

（1）OkHttp3支持的最大并发是64

（2）同一个Host支持的最大并发是5.

（3）调用call.enqueue的方法是异步发起Http请求。

（4）AsyncCall是RealCall的子类，RealCall是由Http请求Request创建出来的。

（5）AsyncCall继承自NamedRunnable, NamedRunnable实现了Runnable接口。

那如何发起一个同步的Http请求？

   OkHttpClient mOkHttpClient = new OkHttpClient();        //new Request.Builder()实例化内部类        //通过build方法构建Request对象        Request request = new Request.Builder()                .url("http://112.4.3.136:8080/portalone/homesdk/NetTVUniLogin")                .addHeader("name", "test")                .build();        Call call = mOkHttpClient.newCall(request);        try {            //通过调用RealCall的execute去主动的发起一次请求            Response response = call.execute();        } catch (IOException e) {            e.printStackTrace();        }

请求/响应流程序分析

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