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Okhttp源码分析--根基使用流程分析 一、 使用 同步请求 OkHttpClient okHttpClient=new OkHttpClient(); Request request=new Request.Builder() .get() .url("") .build(); Call call =okHttpClient.newCall(request).execute(); 异步请求 OkHttpClient okHttpClient=new OkHttpClient(); Request request=new Request.Builder() .get() .url("") .build(); Call call=okHttpClient.newCall(request).enqueue(new Callback() { @Override public void onFailure(Call call, IOException e) { Log.i(TAG, "onFailure: "); } @Override public void onResponse(Call call, Response response) throws IOException { Log.i(TAG, "onResponse: "); } });

可以看出不管是同步还是异步请求，使用okhttp大抵分为3个法式：
1. 创建okhttpclient
2. 创建请求的request
3. 通过client拿到call、发送请求

注：okhttpclient和request的创建均可给与结构者模式，在结构过程中可按照本身的实际需求设置相应的参数，如可在okhttpclient结构时添加自界说拦截器，在request结构过程中设置连接超不时间等。

二、 源码分析

首先看下OkhttpClient这个类，使用法式的第一步就是结构OkhttpClient东西。

先贴下官方对OkhttpClient的界说

*Factory for {@linkplain Call calls}, which can be used to send HTTP requests and read their * responses. * OkHttpClients should be shared * OkHttp performs best when you create a single {@code OkHttpClient} instance and reuse it for * all of your HTTP calls. This is because each client holds its own connection pool and thread * pools. Reusing connections and threads reduces latency and saves memory. Conversely, creating a * client for each request wastes resources on idle pools.

OkhttpClient是用于发送请求和读取响应的，官方建议创建一个单例的OkHttpClient，并且所有的http请求都复用它。因为每个OkHttpClient都有本身的connection pool and thread pool。复用connection pool and thread pool可以节约内存，相反如果为每个请求都创建一个OkHttpClient那么会浪费idle pools中的资源。

创建OkHttpClient有两种方法：
1、通过结构函数
2、通过Builder()创建一个client并自界说设置

同时还供给了一个newBuilder()来自界说client，它跟共享的client拥有不异的connection pool, thread pools, and configuration。我们可以用该要领来获取特定设置的client。

OkHttpClient供给无参结构函数，由代码可知它在内部挪用OkHttpClient的有参结构函数
，在有参结构函数里对OkHttpClient主要属性做了初始化赋值。

public OkHttpClient() { this(new Builder()); } OkHttpClient(Builder builder) { this.dispatcher = builder.dispatcher; this.proxy = builder.proxy; this.protocols = builder.protocols; this.connectionSpecs = builder.connectionSpecs; this.interceptors = Util.immutableList(builder.interceptors); this.networkInterceptors = Util.immutableList(builder.networkInterceptors); this.eventListenerFactory = builder.eventListenerFactory; this.proxySelector = builder.proxySelector; this.cookieJar = builder.cookieJar; this.cache = builder.cache; this.internalCache = builder.internalCache; this.socketFactory = builder.socketFactory; ...//省略N行 }

下面贴下OkHttpClient主要的属性

public class OkHttpClient{ final Dispatcher dispatcher;//分发器 final @Nullable Proxy proxy;//代办代理 final List<Protocol> protocols;//协议 final List<ConnectionSpec> connectionSpecs;//传输层版本和连接协议 final List<Interceptor> interceptors;//拦截器 （okhttp核心机制） final List<Interceptor> networkInterceptors;//网络拦截器 final EventListener.Factory eventListenerFactory; final ProxySelector proxySelector;//代办代理选择器 final CookieJar cookieJar;//cookie final @Nullable Cache cache;//cache 缓存 final @Nullable InternalCache internalCache;//内部缓存 final SocketFactory socketFactory;//socket 工厂 final @Nullable SSLSocketFactory sslSocketFactory;//安适套层socket工厂 用于https final @Nullable CertificateChainCleaner certificateChainCleaner;//验证确认响应书，适用HTTPS 请求连接的主机名 final HostnameVerifier hostnameVerifier;//主机名字确认 final CertificatePinner certificatePinner;//证书链 final Authenticator proxyAuthenticator;//代办代理身份验证 final Authenticator authenticator;//本地省份验证 final ConnectionPool connectionPool;//链接池 复用连接 final Dns dns; //域名 final boolean followSslRedirects;//安适套接层重定向 final boolean followRedirects;//本地重定向 final boolean retryOnConnectionFailure;//连接掉败是否重试 final int connectTimeout;//连接超不时间 final int readTimeout;//读取超不时间 final int writeTimeout;//写入超不时间 }

通过浏览源码我们可以发明OkHttpClient给与了结构者设计模式，这样简化参数设置，降低使用本钱。好比我们前面简单使用的例子