OKHttp使用详解

  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);
    return chain.proceed(originalRequest);
  }

RealConnection get(Address address, StreamAllocation streamAllocation, Route route) {
    assert (Thread.holdsLock(this));
    for (RealConnection connection : connections) {
      if (connection.isEligible(address, route)) {
        streamAllocation.acquire(connection, true);
        return connection;
      }
    }
    return null;
  }

public final class ConnectionPool {
    void put(RealConnection connection) {
        if (!cleanupRunning) {
            //没有连接的时候调用
            cleanupRunning = true;
            executor.execute(cleanupRunnable);
        }
        connections.add(connection);
    }
}

private final Runnable cleanupRunnable = new Runnable() {
        @Override
        public void run() {
            while (true) {
                //执行清理，并返回下次需要清理的时间。
                long waitNanos = cleanup(System.nanoTime());
                if (waitNanos == -1) return;
                if (waitNanos > 0) {
                    long waitMillis = waitNanos / 1000000L;
                    waitNanos -= (waitMillis * 1000000L);
                    synchronized (ConnectionPool.this) {
                        //在timeout时间内释放锁
                        try {
                            ConnectionPool.this.wait(waitMillis, (int) waitNanos);
                        } catch (InterruptedException ignored) {
                        }
                    }
                }
            }
        }
    };

long cleanup(long now) {
    synchronized (this) {
      //遍历连接
      for (Iterator<RealConnection> i = connections.iterator(); i.hasNext(); ) {
        RealConnection connection = i.next();
        //检查连接是否是空闲状态，
        //不是，则inUseConnectionCount + 1
        //是 ，则idleConnectionCount + 1
        if (pruneAndGetAllocationCount(connection, now) > 0) {
          inUseConnectionCount++;
          continue;
        }
        idleConnectionCount++;
        // If the connection is ready to be evicted, we're done.
        long idleDurationNs = now - connection.idleAtNanos;
        if (idleDurationNs > longestIdleDurationNs) {
          longestIdleDurationNs = idleDurationNs;
          longestIdleConnection = connection;
        }
      }
      //如果超过keepAliveDurationNs或maxIdleConnections，
      //从双端队列connections中移除
      if (longestIdleDurationNs >= this.keepAliveDurationNs
          || idleConnectionCount > this.maxIdleConnections) {      
        connections.remove(longestIdleConnection);
      } else if (idleConnectionCount > 0) {      //如果空闲连接次数>0,返回将要到期的时间
        // A connection will be ready to evict soon.
        return keepAliveDurationNs - longestIdleDurationNs;
      } else if (inUseConnectionCount > 0) {
        // 连接依然在使用中，返回保持连接的周期5分钟
        return keepAliveDurationNs;
      } else {
        // No connections, idle or in use.
        cleanupRunning = false;
        return -1;
      }
    }
    closeQuietly(longestIdleConnection.socket());
    // Cleanup again immediately.
    return 0;
  }

  public void acquire(RealConnection connection, boolean reportedAcquired) {
    assert (Thread.holdsLock(connectionPool));
    if (this.connection != null) throw new IllegalStateException();
    this.connection = connection;
    this.reportedAcquired = reportedAcquired;
    connection.allocations.add(new StreamAllocationReference(this, callStackTrace));
  }

public class Request {
  public static class Builder {
    @Nullable HttpUrl url;
    String method;
    Headers.Builder headers;
    @Nullable RequestBody body;
    public Request build() {
      return new Request(this);
    }
  }
}

    CacheStrategy strategy = new CacheStrategy.Factory(now, chain.request(), cacheCandidate).get();
    public Factory(long nowMillis, Request request, Response cacheResponse) {
      this.nowMillis = nowMillis;
      this.request = request;
      this.cacheResponse = cacheResponse;
      if (cacheResponse != null) {
        this.sentRequestMillis = cacheResponse.sentRequestAtMillis();
        this.receivedResponseMillis = cacheResponse.receivedResponseAtMillis();
        Headers headers = cacheResponse.headers();
        for (int i = 0, size = headers.size(); i < size; i++) {
          String fieldName = headers.name(i);
          String value = headers.value(i);
          if ("Date".equalsIgnoreCase(fieldName)) {
            servedDate = HttpDate.parse(value);
            servedDateString = value;
          } else if ("Expires".equalsIgnoreCase(fieldName)) {
            expires = HttpDate.parse(value);
          } else if ("Last-Modified".equalsIgnoreCase(fieldName)) {
            lastModified = HttpDate.parse(value);
            lastModifiedString = value;
          } else if ("ETag".equalsIgnoreCase(fieldName)) {
            etag = value;
          } else if ("Age".equalsIgnoreCase(fieldName)) {
            ageSeconds = HttpHeaders.parseSeconds(value, -1);
          }
        }
      }
    }
 

  final WebSocketListener listener;
  @Override public void onReadMessage(String text) throws IOException {
    listener.onMessage(this, text);
  }