okhttp源码简单流程分析

拦截器详细解析可以看大佬简书 "https://www.jianshu.com/p/6fac73f7570f"和 “https://www.jianshu.com/p/3c740829475c”

okhttp源码简单流程分析_第1张图片

okhttp请求流程
1:OkHttpClient okHttpClient = new OkHttpClient.Builder()
构建一个okhttpClient对象,传入你想传入的对象,不传就是默认的;
2:构建request对象
Request request = new Request.Builder()
3:okHttpClient.newCall 实际上返回的realCall类 继续调用RealCall.newRealCall
4:调用enqueue方法,传入我们需要的回调接口,而且会判断,
synchronized (this) {
if (executed) throw new IllegalStateException(“Already Executed”);
executed = true;
}
如果当前这个call对象已经被运行的话,则抛出异常;
5:继续调用dispatcher的enqueue方法,如果当前运行队列<64并且正在运行,访问同一个服务器地址的请求<5
就直接添加到运行队列,并且开始运行;
不然就添加到等待队列;
6:运行AsyncCall,调用它的execute方法
7:在execute方法中处理完response之后,会在finally中调用dispathcer的finished方法;
8:当当前已经处理完毕的call从运行队列中移除掉;并且调用promoteCalls方法
9:promoteCalls方法中进行判断,
如果运行队列数目大于等于64,如果等待队列里啥都没有,也直接return?
循环等待队列,
将等待队列中的数据进行移除,移除是根据运行队列中还能存放多少来决定;
移到了运行队列中,并且开始运行;

OkHttpClient okHttpClient = new OkHttpClient.Builder().build();
        Request request = new Request.Builder().build();
        //newCall方法是调用RealCall的newRealCall返回一个RealCall
        Call call = okHttpClient.newCall(request);
        //执行请求
        call.enqueue(new Callback() {
            @Override
            public void onFailure(Call call, IOException e) {

            }

            @Override
            public void onResponse(Call call, Response response) throws IOException {

            }
        });
        //这里第二次执行会直接报IllegalStateException错误并提示Already Executed
        call.enqueue(new Callback() {
            @Override
            public void onFailure(Call call, IOException e) {

            }

            @Override
            public void onResponse(Call call, Response response) throws IOException {
                
            }
        });

进入call.enqueue方法

@Override public void enqueue(Callback responseCallback) {
	//这个锁是为了防止重复请求 如果你同一个call enqueue多次就会直接返回Already Executed
    synchronized (this) {
      if (executed) throw new IllegalStateException("Already Executed");
      executed = true;
    }
    captureCallStackTrace();
    eventListener.callStart(this);
    //这里的enqueue是传入任务线程AsyncCall并分配到运行队列或等待队列
    client.dispatcher().enqueue(new AsyncCall(responseCallback));
  }

进入enqueue方法

//okhttp里执行任务分为两个队列 运行队列和等待队列
synchronized void enqueue(AsyncCall call) {
	//当运行的队列中的数值小于64, 
	//并且同时访问同一个机器目标HOST请求书小于5直接加入到运行队列不然的话就加入到等待队列
    if (runningAsyncCalls.size() < maxRequests && runningCallsForHost(call) < maxRequestsPerHost) {
      runningAsyncCalls.add(call);
      //这里维护着请求用的线程池
      executorService().execute(call);
    } else {
      readyAsyncCalls.add(call);
    }
  }
  public synchronized ExecutorService executorService() {
    if (executorService == null) {
    //1:核心线程数 保持在线程池中的线程数量
	//2:线程池最大可容纳的线程数  
	//3参数:当线程池中的线程数量大于核心线程数,空闲线程就会等待60s才会被终止,如果小于就会立刻停止;
      executorService = new ThreadPoolExecutor(0, Integer.MAX_VALUE, 60, TimeUnit.SECONDS,
          new SynchronousQueue<Runnable>(), Util.threadFactory("OkHttp Dispatcher", false));
    }
    return executorService;
  }
//这个就是队列中传入的线程NameRunnable继承自Runnable
final class AsyncCall extends NamedRunnable {
    private final Callback responseCallback;

    AsyncCall(Callback responseCallback) {
      super("OkHttp %s", redactedUrl());
      this.responseCallback = responseCallback;
    }

    String host() {
      return originalRequest.url().host();
    }

    Request request() {
      return originalRequest;
    }

    RealCall get() {
      return RealCall.this;
    }

	//这个就是Async的run方法
    @Override protected void execute() {
      boolean signalledCallback = false;
      try {
      	//getResponseWithInterceptorChain() 添加拦截器 okhttp的责任链设计也在这里
      	//response就是请求结果
        Response response = getResponseWithInterceptorChain();
        //判断重试/重定向拦截器是否被关闭
        if (retryAndFollowUpInterceptor.isCanceled()) {
          signalledCallback = true;
          responseCallback.onFailure(RealCall.this, new IOException("Canceled"));
        } else {
          signalledCallback = true;
          //返回结果
          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 {
      	//将执行完成的任务从队列中移除
        client.dispatcher().finished(this);
      }
    }
  }

添加拦截器

//添加拦截器 责任链设计 
//拦截器详细解析可以看大佬简书 "https://www.jianshu.com/p/6fac73f7570f"和 "https://www.jianshu.com/p/3c740829475c"
Response getResponseWithInterceptorChain() throws IOException {
    // Build a full stack of interceptors.
    List<Interceptor> interceptors = new ArrayList<>();
    interceptors.addAll(client.interceptors());
    //重试/重定向拦截器 连接失败后进行重试、对请求结果跟进后进行重定向
    interceptors.add(retryAndFollowUpInterceptor);
    //桥拦截器:连接应用程序和服务器的桥梁,我们发出的请求会经过它的处理才能发给服务器,
    //比如设置请求内容的长度 封装header属性 host keep-live gzip header 进行基本设置,
    interceptors.add(new BridgeInterceptor(client.cookieJar()));
    //缓存拦截器 在发出请求前,先判断是否命中缓存,
    //如果命中则可以不请求,直接使用缓存的响应(默认只会对Get请求进行缓存);
    //如果未命中则进行网络请求,并将结果缓存,等待下次请求被命中。
    interceptors.add(new CacheInterceptor(client.internalCache()));
    //连接拦截器 与服务器建立连接。
    interceptors.add(new ConnectInterceptor(client));
    if (!forWebSocket) {
      interceptors.addAll(client.networkInterceptors());
    }
    //与服务器通信;封装请求数据与解析响应数据(如:HTTP报文)。
    interceptors.add(new CallServerInterceptor(forWebSocket));
	
    Interceptor.Chain chain = new RealInterceptorChain(interceptors, null, null, null, 0,
        originalRequest, this, eventListener, client.connectTimeoutMillis(),
        client.readTimeoutMillis(), client.writeTimeoutMillis());
	//执行拦截器
    return chain.proceed(originalRequest);
  }

在execute方法中处理完response之后,会在finally中调用dispathcer的finished方法;

//将当前已经处理完毕的call从运行队列中移除掉;并且调用promoteCalls方法
private <T> void finished(Deque<T> calls, T call, boolean promoteCalls) {
    int runningCallsCount;
    Runnable idleCallback;
    synchronized (this) {
      if (!calls.remove(call)) throw new AssertionError("Call wasn't in-flight!");
      if (promoteCalls) promoteCalls();
      runningCallsCount = runningCallsCount();
      idleCallback = this.idleCallback;
    }

    if (runningCallsCount == 0 && idleCallback != null) {
      idleCallback.run();
    }
  }

promoteCalls方法中进行判断

//如果运行队列数目大于等于64,如果等待队列里啥都没有,也直接return
//循环等待队列,
//将等待队列中的数据进行移除,移除是根据运行队列中还能存放多少来决定;
//移到了运行队列中,并且开始运行;

private void promoteCalls() {
    if (runningAsyncCalls.size() >= maxRequests) return; // Already running max capacity.
    if (readyAsyncCalls.isEmpty()) return; // No ready calls to promote.

    for (Iterator<AsyncCall> i = readyAsyncCalls.iterator(); i.hasNext(); ) {
      AsyncCall call = i.next();

      if (runningCallsForHost(call) < maxRequestsPerHost) {
        i.remove();
        runningAsyncCalls.add(call);
        executorService().execute(call);
      }

      if (runningAsyncCalls.size() >= maxRequests) return; // Reached max capacity.
    }
  }

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