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

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