Okhttp3使用 + 源碼完全解析

在使用過okhttp3之後,必然的一步當是對源碼的研究這樣可以對其優劣和功能封裝有一個全面詳盡的了解

ok 下面粘貼okhttp3的核心代碼(url暫時随意定義)

OkHttpClient okHttpClient = new OkHttpClient();
        Request request = new Request.Builder()
                .url("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 {

            }
        });

下面進入正題,來對源碼進行分析

1.okhttp執行個體和Request執行個體和配置

相當于初始化執行個體比較簡單

首先來看okhttp初始化執行個體

1.1 //OkHttpClient okHttpClient = new OkHttpClient();

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


    public Builder() {
      dispatcher = new Dispatcher();
      protocols = DEFAULT_PROTOCOLS;
      connectionSpecs = DEFAULT_CONNECTION_SPECS;
      eventListenerFactory = EventListener.factory(EventListener.NONE);
      proxySelector = ProxySelector.getDefault();
      cookieJar = CookieJar.NO_COOKIES;
      socketFactory = SocketFactory.getDefault();
      hostnameVerifier = OkHostnameVerifier.INSTANCE;
      certificatePinner = CertificatePinner.DEFAULT;
      proxyAuthenticator = Authenticator.NONE;
      authenticator = Authenticator.NONE;
      connectionPool = new ConnectionPool();
      dns = Dns.SYSTEM;
      followSslRedirects = true;
      followRedirects = true;
      retryOnConnectionFailure = true;
      connectTimeout = _000;
      readTimeout = _000;
      writeTimeout = _000;
      pingInterval = ;
    }

其實就是初始化對象和屬性的相關配置過程

1.2Requst的初始化

Request request = new Request.Builder()
                .url("www.baidu.com")
                .build();

下面來看其源碼:

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

  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, , "ws:", , )) {
        url = "http:" + url.substring();
      } else if (url.regionMatches(true, , "wss:", , )) {
        url = "https:" + url.substring();
      }

      HttpUrl parsed = HttpUrl.parse(url);
      if (parsed == null) throw new IllegalArgumentException("unexpected url: " + url);
      return url(parsed);
    }


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

到這裡準備工作就完成了

下面來從請求開始詳細看源碼(以上比較簡單沒有什麼可以講的)

2.請求處理

//Call call = okHttpClient.newCall(request);

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




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;
  }

okhttp3建立請求的主體call對象其實傳回的是一個realCall的執行個體化對象,并完成一系列的相關初始化配置;

下面來看請求

//call.enqueue

@Override 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));
  }

由以上代碼可以看出來 okhttp的請求是由dispatcher來完成的;而dispatcher又是什麼呢 ?

其實是一個網絡的任務排程器;

那麼下面來看下排程器的實作.

3.dispatcher任務排程

//最大請求數
  private int maxRequests = ;
  //最大主機請求數
  private int maxRequestsPerHost = ;
  private @Nullable Runnable idleCallback;
  //消費者線程池
  private @Nullable ExecutorService executorService;
  //将要運作的異步請求隊列
  private final Deque<AsyncCall> readyAsyncCalls = new ArrayDeque<>();
  //正在運作的異步請求隊列
  private final Deque<AsyncCall> runningAsyncCalls = new ArrayDeque<>();
  //正在運作的同步請求隊列
  private final Deque<RealCall> runningSyncCalls = new ArrayDeque<>();

  public Dispatcher(ExecutorService executorService) {
    this.executorService = executorService;
  }

  public Dispatcher() {
  }

Dispatcher主要用于控制并發并且維護了一部分變量

在請求之前dispatcher會自己建立線程池

當然也可以有程式員自己來建立線程池

ok~初步了解排程器之後來看異步請求的源碼

synchronized void enqueue(AsyncCall call) {
    if (runningAsyncCalls.size() < maxRequests && runningCallsForHost(call) < maxRequestsPerHost) {
      runningAsyncCalls.add(call);
      executorService().execute(call);
    } else {
      readyAsyncCalls.add(call);
    }
  }

在排程器的enqueue中會先判斷目前最大請求數和目前最大主機請求數如果不超過預設的最大值則吧請求加入到正在運作的請求隊列—->runningAsyncCalls;

否則會加入到将要運作的請求隊列中進行等待—->readyAsyncCalls

然後 executorService().execute(call);開始運作傳入的線程即傳入的AsyncCall;而AsyncCall作為RealCall的内部實作類會走execute;

ok下面來看AsyncCall–>execute ,在這裡開始進行網絡請求:

@Override 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);
      }
    }
  }

在上面代碼中不難看出走了一系列方法來進行網絡請求為了友善讀者了解先來看finally下的方法 (這個方法必然會走到的):

void finished(AsyncCall call) {
    finished(runningAsyncCalls, call, true);
  }

//finished
  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 ==  && idleCallback != null) {
      idleCallback.run();
    }
  }




//####promoteCalls()
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.
    }
  }

直接提取關鍵代碼:

finished—->if (promoteCalls) promoteCalls(); 當請求完之後 promoteCalls為true 則會走promoteCalls() ;從上面代碼中可圖看出來promoteCalls()中用疊代器周遊readyAsyncCalls 然後加入到runningAsyncCalls

其實就是在請求完成後來請求緩存池中的線程

那麼繼續回頭看AsyncCall–>execute中的邏輯,在這之前先簡單介紹一下攔截器 okhttp中請求有用到攔截器

4.攔截器Interceptors

攔截器主要是用來監聽網絡的請求和響應攔截器的添加可以添加,移除或者轉換請求頭;其實簡單來說就是對網絡請求和響應的一個包裝吧,有興趣可以自己研究一下這裡簡單介紹一下友善接下來的講解;

繼續回到代碼:AsyncCall–>execute:

@Override 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);
      }
    }

上面代碼中關鍵的請求代碼是:

Response response = getResponseWithInterceptorChain();

下面我們來看見其源碼:

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, ,
        originalRequest, this, eventListener, client.connectTimeoutMillis(),
        client.readTimeoutMillis(), client.writeTimeoutMillis());

    return chain.proceed(originalRequest);
  }

在上面代碼中:

Interceptor.Chain chain = new RealInterceptorChain(interceptors, null, null, null, ,
        originalRequest, this, eventListener, client.connectTimeoutMillis(),
        client.readTimeoutMillis(), client.writeTimeoutMillis());

其實是初始化了攔截器傳參為讀取/請求逾時等….

實際請求的代碼是:chain.proceed(originalRequest);

@Override public Response proceed(Request request) throws IOException {
      // If there's another interceptor in the chain, call that.
      if (index < client.interceptors().size()) {
        Interceptor.Chain chain = new ApplicationInterceptorChain(index + , request, forWebSocket);
        //從攔截器清單取出攔截器
        Interceptor interceptor = client.interceptors().get(index);
        Response interceptedResponse = interceptor.intercept(chain);

        if (interceptedResponse == null) {
          throw new NullPointerException("application interceptor " + interceptor
              + " returned null");
        }

        return interceptedResponse;
      }

      // No more interceptors. Do HTTP.
      return getResponse(request, forWebSocket);
    }

在攔截器攔截過程中,當存在多個攔截器,需要攔截等待,即第一個請求完下一個請求;其中攔截的代碼會在上面代碼中:

Interceptor interceptor = client.interceptors().get(index);
        Response interceptedResponse = interceptor.intercept(chain);

而真正請求的代碼是//getResponse(request, forWebSocket);

那麼接着來看它的源碼:

Response getResponse(Request request, boolean forWebSocket) throws IOException {
 //請求成功的核心源碼

    engine = new HttpEngine(client, request, false, false, forWebSocket, null, null, null);

    int followUpCount = ;
    while (true) {
      if (canceled) {
        engine.releaseStreamAllocation();
        throw new IOException("Canceled");
      }

      boolean releaseConnection = true;
      try {
        engine.sendRequest();
        engine.readResponse();
        releaseConnection = false;
      } catch (RequestException e) {
        // The attempt to interpret the request failed. Give up.
        throw e.getCause();
      } catch (RouteException e) {
        ...    
    }


     //請求失敗的核心源碼
     boolean releaseConnection = true;
      try {
        engine.sendRequest();
        engine.readResponse();
        releaseConnection = false;
      } catch (RequestException e) {
        // The attempt to interpret the request failed. Give up.
        throw e.getCause();
      } catch (RouteException e) {
        // The attempt to connect via a route failed. The request will not have been sent.
        HttpEngine retryEngine = engine.recover(e.getLastConnectException(), null);
        if (retryEngine != null) {
          releaseConnection = false;
          engine = retryEngine;
          continue;
        }
        // Give up; recovery is not possible.
        throw e.getLastConnectException();
      } catch (IOException e) {
        // An attempt to communicate with a server failed. The request may have been sent.
        HttpEngine retryEngine = engine.recover(e, null);
        if (retryEngine != null) {
          releaseConnection = false;
          engine = retryEngine;
          continue;
        }

        // Give up; recovery is not possible.
        throw e;
      } finally {
        // We're throwing an unchecked exception. Release any resources.
        if (releaseConnection) {
          StreamAllocation streamAllocation = engine.close();
          streamAllocation.release();
        }
      }
     .....
      engine = new HttpEngine(client, request, false, false, forWebSocket, streamAllocation, null,
          response);
    }

  }

到這裡okhttp3的源碼就解析完畢了感謝支援希望可以幫到你們~

Okhttp3使用 + 源碼完全解析

1.okhttp執行個體和Request執行個體和配置

2.請求處理

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Okhttp3使用 + 源碼完全解析

1.okhttp執行個體 和Request執行個體和配置

2.請求處理

3.dispatcher任務排程

4.攔截器Interceptors

繼續閱讀

1.okhttp執行個體和Request執行個體和配置