Android Open Source - lightbox-android-webservices Database Cleaner Task

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License

The source code is released under:

Apache License

Java Source Code

/**
 * Copyright (c) 2012 Lightbox//  ww w  .  ja  v a  2s  . 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.data;

import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadFactory;

import android.util.Log;

import com.j256.ormlite.dao.Dao;
import com.j256.ormlite.stmt.PreparedQuery;
import com.lightbox.android.operations.Retrievable;
import com.lightbox.android.operations.Updatable;
import com.lightbox.android.tasks.BackgroundTask;

/** 
 * DatabaseCleanerTask 
 * @author Fabien Devos
 */
public class DatabaseCleanerTask extends BackgroundTask<Void> {
  /** Used to tag logs */
  // @SuppressWarnings("unused")
  private static final String TAG = "DatabaseCleanerTask";
    
  // Note: this is the duration for keeping data in the database, that will allow retrieving of data 
  // if OFFLINE mode. This does NOT affect the duration for returning database results rather than trying to fetching
  // the network. See RetreivingOperation for that.
  private static final long DEFAULT_DATABASE_CACHE_DURATION = 7 * 24 * 60 * 60 * 1000; // 1 week
  private static final long USER_DATABASE_CACHE_DURATION = 3 * 7 * 24 * 60 * 60 * 1000; // 3 weeks
  
  private static ExecutorService sDatabaseCleanerExecutor;
  
  /**
   * Constructor.
   */
  public DatabaseCleanerTask() {
    super(getExecutor());
  }
  
  private static ExecutorService getExecutor() {
    if (sDatabaseCleanerExecutor == null) {
      sDatabaseCleanerExecutor = Executors.newSingleThreadExecutor(
          new ThreadFactory() {
            @Override
            public Thread newThread(Runnable r) {
              Thread thread = new Thread(r);
              thread.setName(TAG + " | " + thread.getName());
              thread.setPriority(Thread.MIN_PRIORITY);
              return thread;
            }
          });
    }
    return sDatabaseCleanerExecutor;
  }

  @Override
  protected Void doWorkInBackground() throws Exception {
    try {
      final long DEFAULT_CUTOFF_TIME = System.currentTimeMillis() - DEFAULT_DATABASE_CACHE_DURATION;
      for (Class<?> dataClass : DatabaseHelper.getDataClasses()) {
        if (Updatable.class.isAssignableFrom(dataClass)) {
          long cutoffTime;
//          if (dataClass == User.class) {
//            cutoffTime = System.currentTimeMillis() - USER_DATABASE_CACHE_DURATION;
//          } else {
            cutoffTime = DEFAULT_CUTOFF_TIME;
//          }
          cleanUpOlderThan(cutoffTime, dataClass);
        }
      }
      
    } catch (Throwable t) {
      // We NEVER want to crash while performing a clean-up
      Log.w(TAG, "Unable to complete database clean-up.", t);
    }
    return null;
  }
  
  private static <T> void cleanUpOlderThan(long cutoffTime, Class<T> dataClass) throws Exception {
      Dao<T, String> dao = Data.getDao(dataClass);
      PreparedQuery<T> query = dao.queryBuilder()
          .where().lt(Retrievable.RETRIEVED_TIME, cutoffTime).prepare();
      List<T> oldDataList = dao.query(query);
      for (T data : oldDataList) {
        // Prevent deletion of objects with local updates
        boolean canDelete = true;
        if (data instanceof Updatable) {
          Updatable updatable = (Updatable) data;
          canDelete = (updatable.getLocallyUpdatedFields().isEmpty() && ! updatable.isMarkedAsLocallyDeleted());
        }

        if (canDelete) {
          dao.delete(data);
        }
      }
  }

  @Override
  protected void onCompleted(Void result) {
    // Nothing
  }

  @Override
  protected void onFailed(Exception e) {
    // Nothing
  }
  
}

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