1. Glide 内部使用 HttpURLConnection 执行网络请求

public class HttpUrlFetcher implements DataFetcher<InputStream> {}

private InputStream loadDataWithRedirects(URL url, int redirects, URL lastUrl,
      Map<String, String> headers) throws IOException {
    if (redirects >= MAXIMUM_REDIRECTS) {
      throw new HttpException("Too many (> " + MAXIMUM_REDIRECTS + ") redirects!");
    } else {
      // Comparing the URLs using .equals performs additional network I/O and is generally broken.
      // See http://michaelscharf.blogspot.com/2006/11/javaneturlequals-and-hashcode-make.html.
      try {
        if (lastUrl != null && url.toURI().equals(lastUrl.toURI())) {
          throw new HttpException("In re-direct loop");

        }
      } catch (URISyntaxException e) {
        // Do nothing, this is best effort.
      }
    }

    urlConnection = connectionFactory.build(url);
    for (Map.Entry<String, String> headerEntry : headers.entrySet()) {
      urlConnection.addRequestProperty(headerEntry.getKey(), headerEntry.getValue());
    }
    urlConnection.setConnectTimeout(timeout);
    urlConnection.setReadTimeout(timeout);
    urlConnection.setUseCaches(false);
    urlConnection.setDoInput(true);

    // Stop the urlConnection instance of HttpUrlConnection from following redirects so that
    // redirects will be handled by recursive calls to this method, loadDataWithRedirects.
    urlConnection.setInstanceFollowRedirects(false);

    // Connect explicitly to avoid errors in decoders if connection fails.
    urlConnection.connect();
    // Set the stream so that it's closed in cleanup to avoid resource leaks. See #2352.
    stream = urlConnection.getInputStream();
    if (isCancelled) {
      return null;
    }
    final int statusCode = urlConnection.getResponseCode();
    if (statusCode / 100 == 2) {
      return getStreamForSuccessfulRequest(urlConnection);
    } else if (statusCode / 100 == 3) {
      String redirectUrlString = urlConnection.getHeaderField("Location");
      if (TextUtils.isEmpty(redirectUrlString)) {
        throw new HttpException("Received empty or null redirect url");
      }
      URL redirectUrl = new URL(url, redirectUrlString);
      // Closing the stream specifically is required to avoid leaking ResponseBodys in addition
      // to disconnecting the url connection below. See #2352.
      cleanup();
      return loadDataWithRedirects(redirectUrl, redirects + 1, url, headers);
    } else if (statusCode == -1) {
      throw new HttpException(statusCode);
    } else {
      throw new HttpException(urlConnection.getResponseMessage(), statusCode);
    }
  }

1. Glide 的线程池

public final class GlideExecutor extends ThreadPoolExecutor {}

GlideExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTimeInMs, String name,
      UncaughtThrowableStrategy uncaughtThrowableStrategy, boolean preventNetworkOperations,
      boolean executeSynchronously, BlockingQueue<Runnable> queue) {
    super(
        corePoolSize,
        maximumPoolSize,
        keepAliveTimeInMs,
        TimeUnit.MILLISECONDS,
        queue,
        new DefaultThreadFactory(name, uncaughtThrowableStrategy, preventNetworkOperations));
    this.executeSynchronously = executeSynchronously;
  }

 private static final class DefaultThreadFactory implements ThreadFactory {
    private final String name;
    @Synthetic final UncaughtThrowableStrategy uncaughtThrowableStrategy;
    @Synthetic final boolean preventNetworkOperations;
    private int threadNum;

    DefaultThreadFactory(String name, UncaughtThrowableStrategy uncaughtThrowableStrategy,
        boolean preventNetworkOperations) {
      this.name = name;
      this.uncaughtThrowableStrategy = uncaughtThrowableStrategy;
      this.preventNetworkOperations = preventNetworkOperations;
    }

    @Override
    public synchronized Thread newThread(@NonNull Runnable runnable) {
      final Thread result = new Thread(runnable, "glide-" + name + "-thread-" + threadNum) {
        @Override
        public void run() {
          android.os.Process.setThreadPriority(
              android.os.Process.THREAD_PRIORITY_BACKGROUND
              + android.os.Process.THREAD_PRIORITY_MORE_FAVORABLE);
          if (preventNetworkOperations) {
            StrictMode.setThreadPolicy(
                new ThreadPolicy.Builder()
                    .detectNetwork()
                    .penaltyDeath()
                    .build());
          }
          try {
            super.run();
          } catch (Throwable t) {
            uncaughtThrowableStrategy.handle(t);
          }
        }
      };
      threadNum++;
      return result;
    }
  }
}

1. 数据回调

 interface DataCallback<T> {

    void onDataReady(@Nullable T data);

    void onLoadFailed(Exception e);
  }

链接：http://blog.csdn.net/u013510838/article/details/52143113