okhttp

https://square.github.io/okhttp/
https://github.com/square/okhttp/

0 概述

okhttp是一个现代的网络请求框架

• Http/2 支持 所有访问同一个主机的Request都共用一个socket

• connection pool 连接池 减少请求延迟

• GZIP 压缩数据，减少传输所用的带宽

• Response Cache 避免重复性的Request

---

1 使用

Get

OkHttpClient client = new OkHttpClient();

String run(String url) throws IOException {
  Request request = new Request.Builder()
      .url(url)
      .build();

  try (Response response = client.newCall(request).execute()) {
    return response.body().string();
  }
}

Post

public static final MediaType JSON
    = MediaType.get("application/json; charset=utf-8");

OkHttpClient client = new OkHttpClient();

String post(String url, String json) throws IOException {
  RequestBody body = RequestBody.create(json, JSON);
  Request request = new Request.Builder()
      .url(url)
      .post(body)
      .build();
  try (Response response = client.newCall(request).execute()) {
    return response.body().string();
  }
}

Async

  private final OkHttpClient client = new OkHttpClient();

  public void run() throws Exception {
    Request request = new Request.Builder()
        .url("http://publicobject.com/helloworld.txt")
        .build();

    client.newCall(request).enqueue(new Callback() {
      @Override public void onFailure(Call call, IOException e) {
        e.printStackTrace();
      }

      @Override public void onResponse(Call call, Response response) throws IOException {
        try (ResponseBody responseBody = response.body()) {
          if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);

          Headers responseHeaders = response.headers();
          for (int i = 0, size = responseHeaders.size(); i < size; i++) {
            System.out.println(responseHeaders.name(i) + ": " + responseHeaders.value(i));
          }

          System.out.println(responseBody.string());
        }
      }
    });
  }

---

2 源码

2.0 请求过程

请求 异步

2.1 OkHttpClient

• dispatcher

• interceptors

• networkInterceptors

• connectionPool

• proxy

• newCall()

2.2 Call

• Response execute()

• enqueue(Callback responseCallback)

2.3 Request

• url

• method

• headers

• body

• tag

• cacheControl

2.4 Response

• request

• protocol

• code

• message

• headers

• body

• handshake

2.5 RealInterceptorChain

• interceptors

• transmitter

• index

• request

• call

• exchange

2.6 Interceptor

• Response intercept(Chain chain)

2.7 Cache

• DiskLruCache cache;

2.8 Connection

• Route route();

• Socket socket();

• Handshake handshake();

• Protocol protocol();

• connectSocket

• source

• sink

• connectionPool

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3 架构

• 中间层

  • OKhttp 通过很多中间拦截器来对 Request Response 进行加工

  • 实现了数据的 流式链式处理

• 生产者

• 分发器

  • 调度器 通过不同状态的 任务队列 来调度任务
  • readyCalls runningCalls

• 消费者

• 缓存

• 拦截器
  • 类似责任链的效果，链式处理，链式返回