源码系列-OkHttp---用户3112896

OkHttp官网地址：https://square.github.io/okhttp/

用法如下：（get请求）

package okhttp3.guide; import java.io.IOException;import okhttp3.OkHttpClient;import okhttp3.Request;import okhttp3.Response; public class GetExample { 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(); } } public static void main(String[] args) throws IOException { GetExample example = new GetExample(); String response = example.run("https://raw.github.com/square/okhttp/master/README.md"); System.out.println(response); }}

Github下载源码地址https://github.com/square/okhttp

4.x以上的版本都大部分更新为kotlin了，可以更改分支下载3.x的版本来看

一、先来看第一步构造函数

OkHttpClient client = new OkHttpClient();

源码：

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

Builder()中就是初始化了一堆变量，没啥东西

二、来看get请求

new Request.Builder()

源码：找内部类Builder的构造函数

public Builder() { this.method = "GET"; this.headers = new Headers.Builder();}

源码：接着找Headers的内部类Builder，暂时构造了一个变量，还没有做什么

三、下面是执行.url方法，当然是Request内部类Builder的url方法，url暂定为String

源码：

public Builder url(String url) { if (url == null) throw new NullPointerException("url == null"); // Silently replace web socket URLs with HTTP URLs. if (url.regionMatches(true, 0, "ws:", 0, 3)) { url = "http:" + url.substring(3); } else if (url.regionMatches(true, 0, "wss:", 0, 4)) { url = "https:" + url.substring(4); } return url(HttpUrl.get(url));}

前面是加前缀，后面去到HttpUrl里去

public static HttpUrl get(String url) { return new Builder().parse(null, url).build(); }

HttpUrl的内部类Builder的构造函数

public Builder() { encodedPathSegments.add(""); // The default path is '/' which needs a trailing space.}

encodedPathSegments是一个ArrayList

HttpUrl的内部类Builder的parse方法就是一连串的参数解析，大家可以看源码

最后一个build()方法

public HttpUrl build() { if (scheme == null) throw new IllegalStateException("scheme == null"); if (host == null) throw new IllegalStateException("host == null"); return new HttpUrl(this);}

这个HttpUrl的带参构造函数中也是一堆变量的初始化

回到Request内部类Builder的url方法

public Builder url(HttpUrl url) { if (url == null) throw new NullPointerException("url == null"); this.url = url; return this;}

接着是Request内部类Builder的build方法

public Request build() { if (url == null) throw new IllegalStateException("url == null"); return new Request(this);}

Request的带参构造函数

Request(Builder builder) { this.url = builder.url; this.method = builder.method; this.headers = builder.headers.build(); this.body = builder.body; this.tags = Util.immutableMap(builder.tags);}

四。接下来很重要了，是执行请求

Response response = client.newCall(request).execute()

OkHttpClient中的newCall方法

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

进到RealCall中的newRealCall方法

static RealCall newRealCall(OkHttpClient client, Request originalRequest, boolean forWebSocket) { // Safely publish the Call instance to the EventListener. RealCall call = new RealCall(client, originalRequest, forWebSocket); call.transmitter = new Transmitter(client, call); return call;}

构造函数不用管，进去Transmitter中的构造函数

public Transmitter(OkHttpClient client, Call call) { this.client = client; this.connectionPool = Internal.instance.realConnectionPool(client.connectionPool()); this.call = call; this.eventListener = client.eventListenerFactory().create(call); this.timeout.timeout(client.callTimeoutMillis(), MILLISECONDS);}

其中这个Internal.instance.realConnectionPool(client.connectionPool())可以找到OkHttpClient的static代码块执行后返回了一个RealConnectionPool

private static final Executor executor = new ThreadPoolExecutor(0 /* corePoolSize */, Integer.MAX_VALUE /* maximumPoolSize */, 60L /* keepAliveTime */, TimeUnit.SECONDS, new SynchronousQueue<>(), Util.threadFactory("OkHttp ConnectionPool", true));

RealConnectionPool一看就知道是0个核心线程，最大值个非核心线程的线程池；这里还出现了一个Deque双端队列，即队列的升级版，两个端口都可以进出元素，更加灵活

最后就是RealCall的execute方法了，注意RealCall里有个内部类AsyncCall也有execute方法，注意不要搞混了

@Override public Response execute() throws IOException { synchronized (this) { if (executed) throw new IllegalStateException("Already Executed"); executed = true; } transmitter.timeoutEnter(); transmitter.callStart(); try { client.dispatcher().executed(this); return getResponseWithInterceptorChain(); } finally { client.dispatcher().finished(this); }}

client.dispatcher().executed(this)执行的是

synchronized void executed(RealCall call) { runningSyncCalls.add(call); }

runningSyncCalls就是我们上面提到的Deque双端队列

下面就是最最核心的getResponseWithInterceptorChain方法

Response getResponseWithInterceptorChain() throws IOException { // Build a full stack of interceptors. List<Interceptor> interceptors = new ArrayList<>(); interceptors.addAll(client.interceptors()); interceptors.add(new RetryAndFollowUpInterceptor(client)); interceptors.add(new BridgeInterceptor(client.cookieJar())); interceptors.add(new CacheInterceptor(client.internalCache())); interceptors.add(new ConnectInterceptor(client)); if (!forWebSocket) { interceptors.addAll(client.networkInterceptors()); } interceptors.add(new CallServerInterceptor(forWebSocket)); Interceptor.Chain chain = new RealInterceptorChain(interceptors, transmitter, null, 0, originalRequest, this, client.connectTimeoutMillis(), client.readTimeoutMillis(), client.writeTimeoutMillis()); boolean calledNoMoreExchanges = false; try { Response response = chain.proceed(originalRequest); if (transmitter.isCanceled()) { closeQuietly(response); throw new IOException("Canceled"); } return response; } catch (IOException e) { calledNoMoreExchanges = true; throw transmitter.noMoreExchanges(e); } finally { if (!calledNoMoreExchanges) { transmitter.noMoreExchanges(null); } }}

RetryAndFollowUpInterceptor重试和跳转拦截器

BridgeInterceptor桥接拦截器，即加请求头和去响应头

CacheInterceptor缓存拦截器

ConnectInterceptor连接拦截器

CallServerInterceptor调用服务拦截器

List添加好全部Interceptor之后，执行chain.proceed(originalRequest)来到RealInterceptorChain中的proceed方法

public Response proceed(Request request, Transmitter transmitter, @Nullable Exchange exchange) throws IOException { if (index >= interceptors.size()) throw new AssertionError(); calls++; // If we already have a stream, confirm that the incoming request will use it. if (this.exchange != null && !this.exchange.connection().supportsUrl(request.url())) { throw new IllegalStateException("network interceptor " + interceptors.get(index - 1) + " must retain the same host and port"); } // If we already have a stream, confirm that this is the only call to chain.proceed(). if (this.exchange != null && calls > 1) { throw new IllegalStateException("network interceptor " + interceptors.get(index - 1) + " must call proceed() exactly once"); } // Call the next interceptor in the chain. RealInterceptorChain next = new RealInterceptorChain(interceptors, transmitter, exchange, index + 1, request, call, connectTimeout, readTimeout, writeTimeout); Interceptor interceptor = interceptors.get(index); Response response = interceptor.intercept(next); // Confirm that the next interceptor made its required call to chain.proceed(). if (exchange != null && index + 1 < interceptors.size() && next.calls != 1) { throw new IllegalStateException("network interceptor " + interceptor + " must call proceed() exactly once"); } // Confirm that the intercepted response isn't null. if (response == null) { throw new NullPointerException("interceptor " + interceptor + " returned null"); } if (response.body() == null) { throw new IllegalStateException( "interceptor " + interceptor + " returned a response with no body"); } return response;}Interceptor interceptor = interceptors.get(index);Response response = interceptor.intercept(next);

一开始传入的index为0，就是从第一个拦截器开始执行每个拦截器的intercept方法，index逐次+1

每个拦截器里都调用chain.proceed，这样所有的拦截器就形成链条。这里每个拦截器的作用就不讲了

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