Android Open Source - epgreader-android U R L Cache

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License

The source code is released under:

Apache License

Java Source Code

package com.jeffpalm.android.util.urls;
//from w w w. j  av a 2s . c o  m
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
import java.util.concurrent.atomic.AtomicBoolean;

import android.content.Context;
import android.util.Log;

import com.jeffpalm.android.epg.app.BuildConfig;
import com.jeffpalm.android.util.Asserts;
import com.jeffpalm.android.util.Util;
import com.jeffpalm.android.util.urls.DatabaseHandler.CachedUrlResult;

public final class URLCache {

  private static final String TAG = "URLCache";

  final DatabaseHandler dbHandler;
  private final long cacheLifetimeMilis;
  private AtomicBoolean initted = new AtomicBoolean(false);

  public URLCache(Context context, long cacheLifetimeMilis) {
    this.dbHandler = new DatabaseHandler(context);
    this.cacheLifetimeMilis = cacheLifetimeMilis;
  }

  public void init() {
    if (!initted.getAndSet(true)) {
      dbHandler.open();
    }
  }

  /**
   * Blocking get of the input stream for the url.
   * 
   * @param url URL from which to read
   * @param force
   * @param timeout timeout in millis, ignored if null
   * @return input stream for the url
   * @throws IOException
   * @throws IllegalStateException
   */
  public InputStream openStream(final String url, boolean force, Integer timeout)
      throws IllegalStateException, IOException {
    IllegalStateException caughtIllegalStateException = null;
    IOException caughtIOException = null;
    try {
      return openStreamInternal(url, force, timeout);
    } catch (IllegalStateException e) {
      caughtIllegalStateException = e;
    } catch (IOException e) {
      caughtIOException = e;
    }
    // If an exception occured and we were forcing the download, get it from the
    // cache.
    if (force) {
      Log.d(TAG, "Could not download, so getting from the cache.");
      return getInputStreamFromCache(url);
    }
    // Rethrow the original exception if we couldn't get a value from the cache.
    if (caughtIllegalStateException != null) {
      throw caughtIllegalStateException;
    }
    if (caughtIOException != null) {
      throw caughtIOException;
    }
    throw new RuntimeException("Couldn't download or retrieve " + url);
  }

  public InputStream openStreamInternal(final String url, boolean force, Integer timeout)
      throws IllegalStateException, IOException {
    init();
    Log.d(TAG, String.format("Looking up %s", url));
    if (!force) {
      InputStream inputStream = getInputStreamFromCache(url);
      if (inputStream != null) {
        return inputStream;
      }
    } else {
      Log.d(TAG, "Forcing download");
    }
    Log.d(TAG, "Opening stream");
    return new WriteToDatabaseOnCloseInputStream(url, Util.openStream(url, timeout), dbHandler);
  }

  private InputStream getInputStreamFromCache(String url) {
    DatabaseHandler.CachedUrlResult urlResult = dbHandler.getUrlResult(url);
    if (urlResult != null) {
      long diff = DatabaseHandler.now() - urlResult.getTimeMillis();
      Log.d(TAG, "Cached result updated " + diff + "ms ago cacheLifetimeMilis="
          + cacheLifetimeMilis);
      if (diff < cacheLifetimeMilis) {
        Log.d(TAG, "Found a cached result");
        String body = urlResult.getBody();
        if (body != null) {
          return new StringInputStream(body);
        }
      } else {
        Log.d(TAG, "No cached result");
      }
    }
    return null;
  }

  public int getNumEntries() {
    init();
    return dbHandler.getNumEntries();
  }
}

Java Source Code List

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