Android视频/音频缓存框架AndroidVideoCache（Okhttp）详解

package com.danikula.videocache;

import android.text.TextUtils;

import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InterruptedIOException;
import java.util.Map;
import java.util.concurrent.TimeUnit;

import com.danikula.videocache.file.MyLog;

import okhttp3.Call;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

import static com.danikula.videocache.ProxyCacheUtils.DEFAULT_BUFFER_SIZE;
import static com.danikula.videocache.ProxyCacheUtils.LOG_TAG;
import static java.net.HttpURLConnection.HTTP_OK;
import static java.net.HttpURLConnection.HTTP_PARTIAL;

/**
 * {@link Source} that uses http resource as source for {@link ProxyCache}.
 *
 * @author Alexey Danilov (danikula@gmail.com).
 * 
 * 从URL 获取数据
 */
public class HttpUrlSource implements Source {

  private static final int MAX_REDIRECTS = 5;
  public final String url;
  private static OkHttpClient okHttpClient = new OkHttpClient();
  private Call requestCall = null;
  private InputStream inputStream;
  private volatile int length = Integer.MIN_VALUE;
  private volatile String mime;
  private Map<String, String> headers;

  public HttpUrlSource(String url) {
    this(url, ProxyCacheUtils.getSupposablyMime(url));
  }

  public HttpUrlSource(String url, Map<String, String> headers) {
    this(url, ProxyCacheUtils.getSupposablyMime(url));
    this.headers = headers;
  }

  public HttpUrlSource(String url, String mime) {
    this.url = Preconditions.checkNotNull(url);
    this.mime = mime;
  }

  public HttpUrlSource(HttpUrlSource source) {
    this.url = source.url;
    this.mime = source.mime;
    this.length = source.length;
  }

  @Override
  public synchronized int length() throws ProxyCacheException {
    if (length == Integer.MIN_VALUE) {
      fetchContentInfo();
    }
    return length;
  }

  @Override
  public void open(int offset) throws ProxyCacheException {
    try {
      Response response = openConnection(offset, -1);
      mime = response.header("Content-Type");
      inputStream = new BufferedInputStream(response.body().byteStream(), DEFAULT_BUFFER_SIZE);
      length = readSourceAvailableBytes(response, offset, response.code());
    } catch (IOException e) {
      throw new ProxyCacheException("Error opening okHttpClient for " + url + " with offset " + offset, e);
    }
  }

  private int readSourceAvailableBytes(Response response, int offset, int responseCode) throws IOException {
    int contentLength = Integer.valueOf(response.header("Content-Length", "-1"));

    return responseCode == HTTP_OK ? contentLength
        : responseCode == HTTP_PARTIAL ? contentLength + offset : length;
  }

  @Override
  public void close() throws ProxyCacheException {
    if (okHttpClient != null && inputStream != null && requestCall != null) {
      try {
        inputStream.close();
        requestCall.cancel();
      } catch (IOException e) {
        e.printStackTrace();
      }
    }
  }

  @Override
  public int read(byte[] buffer) throws ProxyCacheException {
    if (inputStream == null) {
      throw new ProxyCacheException("Error reading data from " + url + ": okHttpClient is absent!");
    }
    try {
      return inputStream.read(buffer, 0, buffer.length);
    } catch (InterruptedIOException e) {
      throw new InterruptedProxyCacheException("Reading source " + url + " is interrupted", e);
    } catch (IOException e) {
      throw new ProxyCacheException("Error reading data from " + url, e);
    }
  }

  private void fetchContentInfo() throws ProxyCacheException {
    MyLog.d(LOG_TAG, "Read content info from " + url);
    Response response = null;
    InputStream inputStream = null;
    try {
      response = openConnection(0, 20000);
      length = Integer.valueOf(response.header("Content-Length", "-1"));
      mime = response.header("Content-Type");
      inputStream = response.body().byteStream();
      MyLog.i(LOG_TAG, "Content info for `" + url + "`: mime: " + mime + ", content-length: " + length);
    } catch (IOException e) {
      MyLog.e(LOG_TAG, "Error fetching info from " + url, e);
    } finally {
      ProxyCacheUtils.close(inputStream);
      if (response != null) {
        requestCall.cancel();
      }
    }
  }

  private Response openConnection(int offset, int timeout) throws IOException, ProxyCacheException {
    boolean redirected;
    int redirectCount = 0;
    String url = this.url;
    Request request = null;
    //do {
      MyLog.d(LOG_TAG, "Open okHttpClient " + (offset > 0 ? " with offset " + offset : "") + " to " + url);
//      okHttpClient = (HttpURLConnection) new URL(url).openConnection();
      Request.Builder builder = new Request.Builder();
      builder.url(url);
      //flac
      if(headers != null) {
        //设置请求头
        for (Map.Entry<String, String> entry : headers.entrySet()) {
          MyLog.i(LOG_TAG, "请求头信息 key:" + entry.getKey() +" Value" + entry.getValue());
//          okHttpClient.setRequestProperty(entry.getKey(), entry.getValue());
          builder.addHeader(entry.getKey(), entry.getValue());
        }
      }
      if (offset > 0) {
        builder.addHeader("Range", "bytes=" + offset + "-");
      }

      request = builder.build();
      requestCall = okHttpClient.newCall(request);
      /*if (redirected) {
        url = okHttpClient.getHeaderField("Location");
        redirectCount++;
        okHttpClient.disconnect();
      }
      if (redirectCount > MAX_REDIRECTS) {
        throw new ProxyCacheException("Too many redirects: " + redirectCount);
      }*/
    //} while (redirected);

    return requestCall.execute();
  }

  public synchronized String getMime() throws ProxyCacheException {
    if (TextUtils.isEmpty(mime)) {
      fetchContentInfo();
    }
    return mime;
  }

  public String getUrl() {
    return url;
  }

  @Override
  public String toString() {
    return "HttpUrlSource{url='" + url + "}";
  }
}