1.基本使用
OkHttpClient okHttpClient = new OkHttpClient(); Request request = new Request.Builder() .url("https://www.baidu.com/") .build(); Call call = okHttpClient.newCall(request); call.enqueue(new Callback() { @Override public void onFailure(Call call, IOException e) { } @Override public void onResponse(Call call, Response response) throws IOException { } });复制代码 2.Request
public static class Builder { HttpUrl url; String method; Headers.Builder headers; RequestBody body; Object tag; public Builder() { this.method = "GET"; this.headers = new Headers.Builder(); } ......}复制代码 Request主要功能是将请求的所有特性封装到一起,从它的成员变量可以看到主要包括url,method,headers,body,tag(主要用来标识这个请求,方便后面来延迟或者取消标识的请求)
3.Call
3.1 Call的创建
public Call newCall(Request request) { return RealCall.newRealCall(this, request, false /* for web socket */); }复制代码 用的是Call的实现类RealCall。关于Call的解释
/** * A call is a request that has been prepared for execution. A call can be canceled. As this object * represents a single request/response pair (stream), it cannot be executed twice. */public interface Call extends Cloneable { Request request(); /** * Invokes the request immediately, and blocks until the response can be processed or is in * error. * * To avoid leaking resources callers should close the {
@link Response} which in turn will * close the underlying { @link ResponseBody}. * * @{code * * // ensure the response (and underlying response body) is closed * try (Response response = client.newCall(request).execute()) { * ... * } * * } * * The caller may read the response body with the response's {
@link Response#body} method. To * avoid leaking resources callers must { @linkplain ResponseBody close the response body} or the * Response. * * Note that transport-layer success (receiving a HTTP response code, headers and body) does * not necessarily indicate application-layer success: {
@code response} may still indicate an * unhappy HTTP response code like 404 or 500. * * @throws IOException if the request could not be executed due to cancellation, a connectivity * problem or timeout. Because networks can fail during an exchange, it is possible that the * remote server accepted the request before the failure. * @throws IllegalStateException when the call has already been executed. */ Response execute() throws IOException; /** * Schedules the request to be executed at some point in the future. * * The {
@link OkHttpClient#dispatcher dispatcher} defines when the request will run: usually * immediately unless there are several other requests currently being executed. * * This client will later call back {
@code responseCallback} with either an HTTP response or a * failure exception. * * @throws IllegalStateException when the call has already been executed. */ void enqueue(Callback responseCallback); /** Cancels the request, if possible. Requests that are already complete cannot be canceled. */ void cancel(); /** * Returns true if this call has been either { @linkplain #execute() executed} or { @linkplain * #enqueue(Callback) enqueued}. It is an error to execute a call more than once. */ boolean isExecuted(); boolean isCanceled(); /** * Create a new, identical call to this one which can be enqueued or executed even if this call * has already been. */ Call clone(); interface Factory { Call newCall(Request request); }}复制代码 Call可以被取消,一个Call最多只能被执行一次Response execute()方法:同步执行,没有response前会阻塞void enqueue(Callback responseCallback)方法:异步执行,执行结果在Callback回调void cancel()方法:取消一个尚未之行结束的request,不过request执行完毕后就不能被取消boolean isExecuted()方法:请求是否已经执行boolean isCanceled()方法:请求是否已经被取消Call clone()方法:复制一个新的Call,并且可以被重新执行,哪怕被复制的Call已经执行
3.2 Call的执行
直接看RealCall的enqueue方法
public void enqueue(Callback responseCallback) { synchronized (this) { if (executed) throw new IllegalStateException("Already Executed"); executed = true; } captureCallStackTrace(); eventListener.callStart(this); client.dispatcher().enqueue(new AsyncCall(responseCallback)); }复制代码 Dispatcher中enqueue方法
synchronized void enqueue(AsyncCall call) { if (runningAsyncCalls.size() < maxRequests && runningCallsForHost(call) < maxRequestsPerHost) { runningAsyncCalls.add(call); executorService().execute(call); } else { readyAsyncCalls.add(call); } }复制代码 正在执行的所有call请求数不能超过maxRequests(64)个，并且同一host的请求不能超过maxRequestsPerHost(5)个,否则就加到等待队列readyAsyncCalls中
public synchronized ExecutorService executorService() { if (executorService == null) { executorService = new ThreadPoolExecutor(0, Integer.MAX_VALUE, 60, TimeUnit.SECONDS, new SynchronousQueue (), Util.threadFactory("OkHttp Dispatcher", false)); } return executorService; }复制代码 最后是通过线程池ThreadPoolExecutor来执行AsyncCall的,AsyncCall继承自NamedRunnable
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();}复制代码 本质就是用线程池执行了一个Runnable.NamedRunnable的run方法中最终会执行execute方法 AsyncCall的execute方法
protected void execute() { boolean signalledCallback = false; try { Response response = getResponseWithInterceptorChain(); if (retryAndFollowUpInterceptor.isCanceled()) { signalledCallback = true; responseCallback.onFailure(RealCall.this, new IOException("Canceled")); } else { signalledCallback = true; responseCallback.onResponse(RealCall.this, response); } } catch (IOException e) { if (signalledCallback) { // Do not signal the callback twice! Platform.get().log(INFO, "Callback failure for " + toLoggableString(), e); } else { eventListener.callFailed(RealCall.this, e); responseCallback.onFailure(RealCall.this, e); } } finally { client.dispatcher().finished(this); } }复制代码 通过getResponseWithInterceptorChain方法拿到请求结果