Android Open Source - lightbox-android-webservices Api Cache

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License

The source code is released under:

Apache License

Java Source Code

/**
 * Copyright (c) 2012 Lightbox//ww w  .  java 2 s .  co  m
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.lightbox.android.cache;

import java.io.File;
import java.io.IOException;
import java.net.URLEncoder;

import org.apache.commons.io.FileUtils;

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

import com.lightbox.android.utils.AndroidUtils;

/** 
 * ApiCache 
 * @author Fabien Devos
 */
public class ApiCache implements Cache<Object, String> {
  /** Used to tag logs */
  //@SuppressWarnings("unused")
  private static final String TAG = "ApiCache";
  
  public static final int MAX_ENTRIES_IN_MEMORY = 100;

  private final String CACHE_DIR;
  private static final Result<String> EMPTY_RESULT = new Result<String>(null, 0);

  //----------------------------------------------------------------------------
  // Singleton pattern
  private ApiCache() {
    Context context = AndroidUtils.getApplicationContext();
    if (context == null) {
      throw new IllegalStateException("You must set an Application context in ANdroidUtils before attempting to use the ApiCache.");
    }
    
    CACHE_DIR = context.getCacheDir().getAbsolutePath() + "/";
  }

  /** ApiCacheHolder is loaded on the first execution of ApiCache.getInstance() 
   * or the first access to ApiCacheHolder.INSTANCE, not before. */
  private static class ApiCacheHolder {
    private static final ApiCache INSTANCE = new ApiCache();
  }

  /** @return a unique instance of the class */
  public static ApiCache getInstance() {
    return ApiCacheHolder.INSTANCE;
  }

  /** Not supported
   * @throws CloneNotSupportedException (every time) */
  public Object clone() throws CloneNotSupportedException {
    // to prevent any kind of cheating
    throw new CloneNotSupportedException();
  }
  //----------------------------------------------------------------------------
  
  @Override
  public void clear() {
    clearDisk();
  }

  //----------------------------------------------
  // Memory cache methods (not supported)
  
  @Override
  public void clearMemory() {
    throw new UnsupportedOperationException("No API memory cache");
  }
    
  @Override
  public Object getFromMemory(String key) {
    throw new UnsupportedOperationException("No API memory cache");
  }
  
  @Override
  public void putInMemory(String key, Object data) {
    throw new UnsupportedOperationException("No API memory cache");
  }
  
  //----------------------------------------------
  // Disk cache methods
  
  @Override
  public boolean existOnDisk(String key) {
    try {
      return getFile(key).exists();
    } catch (IOException e) {
      Log.w(TAG, e);
      return false;
    }
  }
  
  @Override
  public Result<String> getFromDisk(String key, Object... objects) {
    Result<String> result = EMPTY_RESULT;
    
    if (key != null) {
      try {
        File file = getFile(key);
        if (file.exists()) {
          long updatedTime = file.lastModified();
          String string = FileUtils.readFileToString(file);
          result = new Result<String>(string, updatedTime);      
        }
      } catch (IOException e) {
        Log.w(TAG, e);
        // Will return empty result
      }
    }
    return result;
  }

  @Override
  public void putOnDisk(String key, String string) {
    if (key != null && string != null) {
      try {
        File file = getFile(key);
        FileUtils.writeStringToFile(file, string);
      } catch (Exception e) {
        // ignore exception since this is just a cache
        Log.w(TAG, "Unable to save api result", e);
      }
    }
  }

  public void clearFromDisk(String key) {
    if (key != null) {
      try {
        File file = getFile(key);
        FileUtils.deleteQuietly(file);
      } catch (Exception e) {
        Log.w(TAG, "Unable to clear entry", e);
      }
    }
  }
  
  private File getFile(String key) throws IOException {
    //DebugLog.d(TAG, "Encoding key for cache: " + key);
    return new File(CACHE_DIR + URLEncoder.encode(key, "UTF-8"));
  }  
  
  @Override
  public void clearDisk() {
    FileUtils.deleteQuietly(new File(CACHE_DIR));
  }
  
  @Override
  public void startDiskCleanup() {
    // TODO ApiCache clean-up
  }


}

Java Source Code List

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