Android Open Source - TaskButler Backup Manager

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License

The source code is released under:

GNU General Public License

Java Source Code

/* 
 * BackupManager.java//from  ww w.j  ava  2 s  . c  o  m
 * 
 * Copyright 2012 Jonathan Hasenzahl, James Celona, Dhimitraq Jorgji
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package edu.worcester.cs499summer2012.task;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.nio.channels.FileChannel;

import android.os.Environment;
import edu.worcester.cs499summer2012.database.DatabaseHandler;

/**
 * Class to handle backup and restoring of user data (the database and
 * preference file)
 * @author Jonathan Hasenzahl
 */
public class BackupManager {

  public static final String BACKUP_OK = "backup_ok";
  public static final String BACKUP_EXCEPTION = "backup_exception";
  public static final String RESTORE_OK = "restore_ok";
  public static final String RESTORE_EXCEPTION = "restore_exception";
  public static final String NO_RESTORE_EXISTS = "no_restore_exists";
  public static final long NO_BACKUP_EXISTS = 0L;
  
  private static final String PACKAGE_NAME = "edu.worcester.cs499summer2012";
  private static final String DB_FILENAME = DatabaseHandler.DATABASE_NAME;
  private static final String DB_INTERNAL_PATH = "//data//" + PACKAGE_NAME + "//databases//";
  private static final String DB_EXTERNAL_PATH = "//TaskButler//backup//";
  
  public static String interpretStringCode(String code) {
    if (code.equals(BACKUP_OK))
      return "Backup successful!";
    
    if (code.equals(RESTORE_OK))
      return "Restore successful!";
    
    if (code.equals(NO_RESTORE_EXISTS))
      return "No backup exists";
    
    if (code.equals(BACKUP_EXCEPTION))
      return "The backup failed unexpectedly";
    
    if (code.equals(RESTORE_EXCEPTION))
      return "The restore failed unexpectedly";
    
    if (code.equals(Environment.MEDIA_BAD_REMOVAL))
      return "Error: Media was removed before it was unmounted";
    
    if (code.equals(Environment.MEDIA_CHECKING))
      return "Error: Media is being disk-checked";
    
    if (code.equals(Environment.MEDIA_MOUNTED_READ_ONLY))
      return "Error: Media is mounted with read-only access";
    
    if (code.equals(Environment.MEDIA_NOFS))
      return "Error: Media filesystem cannot be recognized";
    
    if (code.equals(Environment.MEDIA_REMOVED))
      return "Error: Media is not present";
    
    if (code.equals(Environment.MEDIA_SHARED))
      return "Error: Media is being shared via USB";
    
    if (code.equals(Environment.MEDIA_UNMOUNTABLE))
      return "Error: Media cannot be mounted";
    
    if (code.equals(Environment.MEDIA_UNMOUNTED))
      return "Error: Media is not mounted";
    
    return "Error: Unknown code";
  }
  
  public BackupManager() {}
  
  /**
   * Returns the date in ms of the backup file.
   * @return the date in ms of the backup file, or -1 if backup does not exist
   */
  public long getBackupDate() {
    String media_state = Environment.getExternalStorageState();
    
    // Check for read access
    if (!media_state.equals(Environment.MEDIA_MOUNTED) && 
        !media_state.equals(Environment.MEDIA_MOUNTED_READ_ONLY))
      return NO_BACKUP_EXISTS;
    
    try {
      File sd_card = Environment.getExternalStorageDirectory();
      
      if (sd_card.canRead()) {
        File backup = new File(sd_card, DB_EXTERNAL_PATH + DB_FILENAME);
        return backup.lastModified();
      } else
        return NO_BACKUP_EXISTS;
      
    } catch (Exception e) {
      return NO_BACKUP_EXISTS;
    }
  }
  
  /**
   * Backs up the app database and preferences file to SD card.
   * @return BACKUP_OK if successful, else a MEDIA code describing why the
   *                   backup was not possible
   */
  public String backup() {
    String media_state = Environment.getExternalStorageState();
    
    // Check for write access
    if (!media_state.equals(Environment.MEDIA_MOUNTED))
      return media_state;
    
    try {
      File sd_card = Environment.getExternalStorageDirectory();
      File internal_storage = Environment.getDataDirectory();
      
      if (sd_card.canWrite()) {
        // Backup database
        File backup_dir = new File(sd_card, DB_EXTERNAL_PATH);
        backup_dir.mkdirs();
        File backup = new File(backup_dir, DB_FILENAME);
        File current = new File(internal_storage, DB_INTERNAL_PATH + DB_FILENAME);
        
        FileInputStream input_stream = new FileInputStream(current);
        FileOutputStream output_stream = new FileOutputStream(backup);
        FileChannel source = input_stream.getChannel();
        FileChannel dest = output_stream.getChannel();
        
        dest.transferFrom(source, 0, source.size());
        source.close();
        dest.close();
        input_stream.close();
        output_stream.close();
      } else {
        return BACKUP_EXCEPTION;
      }
        
    } catch (Exception e) {
      return BACKUP_EXCEPTION;
    }
    
    return BACKUP_OK;
  }
  
  /**
   * Restores the app database and preferences file from SD card.
   * @return RESTORE_OK if successful, else a MEDIA code describing why the
   *                    restore was not possible
   */
  public String restore() {
    String media_state = Environment.getExternalStorageState();
    
    // Check for read access
    if (!media_state.equals(Environment.MEDIA_MOUNTED) && 
        !media_state.equals(Environment.MEDIA_MOUNTED_READ_ONLY))
      return media_state;
    
    try {
      File sd_card = Environment.getExternalStorageDirectory();
      File internal_storage = Environment.getDataDirectory();
      
      if (sd_card.canRead()) {
        // Restore database
        File backup = new File(sd_card, DB_EXTERNAL_PATH + DB_FILENAME);
        if (!backup.exists())
          return NO_RESTORE_EXISTS;
        File restored = new File(internal_storage, DB_INTERNAL_PATH + DB_FILENAME);
        
        FileInputStream input_stream = new FileInputStream(backup);
        FileOutputStream output_stream = new FileOutputStream(restored);
        FileChannel source = input_stream.getChannel();
        FileChannel dest = output_stream.getChannel();
        
        dest.transferFrom(source, 0, source.size());
        source.close();
        dest.close();
        input_stream.close();
        output_stream.close();
      } else
        return RESTORE_EXCEPTION;
      
    } catch (Exception e) {
      return RESTORE_EXCEPTION;
    }
    
    return RESTORE_OK;
  }
  
}

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