Android Okhttp3的使用与运行流程
基本使用
fun okhttp3Demo() {
val client: OkHttpClient = OkHttpClient.Builder().build()//创建OkHttpClient
val r: Request = Request.Builder().url("").build()//创建Request请求
val call:okhttp3.Call = client.newCall(r)//创建一个Call
//添加回调并且添加到等待缓存
call.enqueue(object : okhttp3.Callback {
override fun onFailure(call: okhttp3.Call, e: IOException) {
}
override fun onResponse(call: okhttp3.Call, response: okhttp3.Response) {
}
})
//call.execute()//直接加入运行缓存
}
运行过程图
Call接口的实现类RealCall
HttpClient调用newCall(r:Request)方法 创建Call的实现类RealCall
@Override public Call newCall(Request request) {
return RealCall.newRealCall(this, request, false /* for web socket */);
}
跳转到RealCall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.eventListener = client.eventListenerFactory().create(call);
return call;
}
找到RealCall的enqueue()方法
@Override public void enqueue(Callback responseCallback) {
synchronized (this) {
if (executed) throw new IllegalStateException("Already Executed");
executed = true;
}
captureCallStackTrace();
eventListener.callStart(this);
//调用了HttpClient的Dispatcher的enqueue方法 此时创建了一个Runable的实现类 AsyncCall
client.dispatcher().enqueue(new RealCall.AsyncCall(responseCallback));
}
先看AsyncCall 实现了NamedRunnable接口 NamedRunnable实现了Runnable 其run方法调用了AsyncCall的execute()方法
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();
}
进入AsyncCall方法的execute()
@Override protected void execute() {
try{
//...other
//添加interceptors拦截器 责任链
Response response = getResponseWithInterceptorChain();
//...other
} finally {
client.dispatcher().finished(this);
}
}
Response getResponseWithInterceptorChain() throws IOException {
// Build a full stack of interceptors.
List<Interceptor> interceptors = new ArrayList<>();
interceptors.addAll(client.interceptors());
interceptors.add(retryAndFollowUpInterceptor);
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, null, null, null, 0,
originalRequest, this, eventListener, client.connectTimeoutMillis(),
client.readTimeoutMillis(), client.writeTimeoutMillis());
return chain.proceed(originalRequest);
}
RealInterceptorChain实现拦截器功能 分别调用拦截器的proceed()方法执行网络请求返回Response
Dispatcher
Call看完接着进入HttpClient的Dispatcher的enqueue方法
//准备中的异步队列
private final Deque<RealCall.AsyncCall> readyAsyncCalls = new ArrayDeque<>();
//执行中的异步队列
private final Deque<RealCall.AsyncCall> runningAsyncCalls = new ArrayDeque<>();
//执行中的同步队列
private final Deque<RealCall> runningSyncCalls = new ArrayDeque<>();
void enqueue(RealCall.AsyncCall call) {
synchronized (this) {
readyAsyncCalls.add(call);
}
//处理和执行线程
promoteAndExecute();
}
private boolean promoteAndExecute() {
assert (!Thread.holdsLock(this));
List<RealCall.AsyncCall> executableCalls = new ArrayList<>();
boolean isRunning;
synchronized (this) {//将线程进行缓存处理
for (Iterator<RealCall.AsyncCall> i = readyAsyncCalls.iterator(); i.hasNext(); ) {
//从readyAsyncCalls中取出可执行线程并添加到runningAsyncCalls中 并执行线程
RealCall.AsyncCall asyncCall = i.next();
if (runningAsyncCalls.size() >= maxRequests) break; // Max capacity.
if (runningCallsForHost(asyncCall) >= maxRequestsPerHost) continue; // Host max capacity.
i.remove();
executableCalls.add(asyncCall);
runningAsyncCalls.add(asyncCall);
}
isRunning = runningCallsCount() > 0;
}
for (int i = 0, size = executableCalls.size(); i < size; i++) {
RealCall.AsyncCall asyncCall = executableCalls.get(i);
//调用RealCall的executeOn方法 其内部执行 executorService.execute(this);线程池启动线程
asyncCall.executeOn(executorService());
}
return isRunning;
}
关于Dispatcher内部的线程池--线程池另外写一个随笔
public synchronized ExecutorService executorService() {
if (executorService == null) {
//创建一个线程池
executorService = new ThreadPoolExecutor(0, Integer.MAX_VALUE, 60, TimeUnit.SECONDS,
new SynchronousQueue<Runnable>(), Util.threadFactory("OkHttp Dispatcher", false));
}
return executorService;
}
