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Android Data Michael Pardo

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Android Storage Options • SharedPreferences • Filesystem • SQLite

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Android Storage Options • SharedPreferences • Filesystem • SQLite • Network • NoSQL

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SharedPreferences

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SharedPreferences • Stores key-value pairs as XML • Good for a relatively small collection • Primitive data types only

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Real-world uses • Game item inventory • Application state • User preferences

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8176c32554b6c4a1937cf14580d4afbb

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// Provide a name for the preferences file name SharedPreferences prefs = getSharedPreferences( PREFS_NAME, Context.MODE_PRIVATE);

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// Uses the activity's class name as the preferences file name SharedPreferences prefs = getPreferences(Context.MODE_PRIVATE);

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// Uses the activity's class name as the preferences file name SharedPreferences prefs = getPreferences(Context.MODE_PRIVATE); ! // Same as above SharedPreferences prefs = getSharedPreferences( activity.getLocalClassName(), Context.MODE_PRIVATE);

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// Use package name as the preferences file name SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences( context);

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// Use package name as the preferences file name SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences( context); ! // Same as above SharedPreferences prefs = getSharedPreferences( getPackageName() + "_preferences", Context.MODE_PRIVATE);

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// Get instance of SharedPreferences SharedPreferences prefs = getPreferences(Context.MODE_PRIVATE);

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// Get instance of SharedPreferences SharedPreferences prefs = getPreferences(Context.MODE_PRIVATE); ! // Retrieve stored value boolean firstRun = prefs.getBoolean("firstRun", true);

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// Get instance of SharedPreferences SharedPreferences prefs = getPreferences(Context.MODE_PRIVATE); ! // Retrieve stored value boolean firstRun = prefs.getBoolean("firstRun", true); ! if (firstRun) { // Get instance of editor and persist value SharedPreferences.Editor editor = prefs.edit(); editor.putInt("firstRun", false); editor.commit(); }

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Libraries • Complex Preferences • SimpleSharedPreferences • Typed Preferences

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Complex Preferences // Get instance of ComplexPreferences ComplexPreferences prefs = ComplexPreferences.getComplexPreferences( this, PREFS_NAME, Context.MODE_PRIVATE);

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Complex Preferences // Get instance of ComplexPreferences ComplexPreferences prefs = ComplexPreferences.getComplexPreferences( this, PREFS_NAME, Context.MODE_PRIVATE); ! // Persist Inventory prefs.putObject("inventory", inventory); prefs.commit();

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Complex Preferences // Get instance of ComplexPreferences ComplexPreferences prefs = ComplexPreferences.getComplexPreferences( this, PREFS_NAME, Context.MODE_PRIVATE); ! // Persist Inventory prefs.putObject("inventory", inventory); prefs.commit(); ! // Retrieve Inventory Inventory inventory = prefs.getObject("inventory", Inventory.class);

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SimpleSharedPreferences // Create instance of SimpleSharedPrefernces SimpleSharedPreferences prefs = new SimpleSharedPreferences(context);

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SimpleSharedPreferences // Create instance of SimpleSharedPrefernces SimpleSharedPreferences prefs = new SimpleSharedPreferences(context); ! // Retrieve stored value boolean firstRun = prefs.getBoolean("firstRun", true);

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SimpleSharedPreferences // Create instance of SimpleSharedPrefernces SimpleSharedPreferences prefs = new SimpleSharedPreferences(context); ! // Retrieve stored value boolean firstRun = prefs.getBoolean("firstRun", true); ! if (firstRun) { // Persist value prefs.putBoolean("firstRun", false); }

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Typed Preferences // Get instance of SharedPreferences SharedPreferences prefs = getPreferences(Context.MODE_PRIVATE);

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Typed Preferences // Get instance of SharedPreferences SharedPreferences prefs = getPreferences(Context.MODE_PRIVATE); ! // Create instance of BooleanPreference BooleanPreference firstRun = new BooleanPreference(prefs, "firstRun", true);

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Typed Preferences // Get instance of SharedPreferences SharedPreferences prefs = getPreferences(Context.MODE_PRIVATE); ! // Create instance of BooleanPreference BooleanPreference firstRun = new BooleanPreference(prefs, "firstRun", true); ! // Retrieve stored value if (firstRun.get()) { // Persist value firstRun.set(true); }

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Ease of Use Complexity of Data Amount of Data SharedPreferences Filesystem SQLite

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Filesystem

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Filesystem • Same as Java I/O API • Good for large amounts of data • Internal and external storage

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Internal Storage • Always available • Privately accessible by default • All files removed from internal storage upon uninstallation

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External Storage • Not always available • Publicly accessible • All files removed from getExternalFilesDir() upon uninstallation

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Real-world uses • API request cache • Game state object • Edited images

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JSONObject gameState = game.getState(); ! String fileName = "game_state.json"; String fileContents = gameState.toString(); ! // Use context.openFileOutput() to open an output stream FileOutputStream fos = openFileOutput(fileName, Context.MODE_PRIVATE); ! fos.write(fileContents.getBytes()); fos.close();

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JSONObject gameState = game.getState(); ! String fileName = "game_state.json"; String fileContents = gameState.toString(); ! // Use context.getFilesDir() to open an output stream FileOutputStream fos = new FileOutputStream(new File(getFilesDir(), fileName)); ! fos.write(fileContents.getBytes()); fos.close();

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...

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... ! ! ...

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public boolean isExternalStorageWritable() { String state = Environment.getExternalStorageState(); return state.equals(Environment.MEDIA_MOUNTED); }

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public boolean isExternalStorageWritable() { String state = Environment.getExternalStorageState(); return state.equals(Environment.MEDIA_MOUNTED); } ! public boolean isExternalStorageReadable() { String state = Environment.getExternalStorageState(); return state.equals(Environment.MEDIA_MOUNTED) || state.equals(Environment.MEDIA_MOUNTED_READ_ONLY); }

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context.openFileOutput(String name, int mode); ! context.openFileInput(String name); ! context.getFileStreamPath(String name); ! context.getFilesDir(); ! context.getCacheDir(); ! Environment.getDownloadCacheDirectory(); ! Environment.getExternalStorageDirectory(); ! Environment.getExternalStoragePublicDirectory(String type); ! Environment.getExternalStorageState();

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Libraries • Apache Commons IO • Guava

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Apache Commons IO // Get URL content InputStream in = new URL( "http://developer.android.com" ).openStream(); try { String html = IOUtils.toString(in); } finally { IOUtils.closeQuietly(in); }

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Apache Commons IO // Get file lines File file = new File(getFilesDir() , "todo.txt"); List lines = FileUtils.readLines(file, "UTF-8");

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Apache Commons IO String filename = "/data/data/com.michaelpardo.app/cache/../todo.txt"; String normalized = FilenameUtils.normalize(filename); // result is "/data/data/com.michaelpardo.app/todo.txt"

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Guava // Read the lines of a UTF-8 text file ImmutableList lines = Files.asCharSource(file, Charsets.UTF_8) .readLines();

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Guava // Count distinct word occurrences in a file Multiset wordOccurrences = HashMultiset.create( Splitter.on(CharMatcher.WHITESPACE) .trimResults() .omitEmptyStrings() .split(Files.asCharSource(file, Charsets.UTF_8).read()));

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Guava // SHA-1 a file HashCode hash = Files.asByteSource(file).hash(Hashing.sha1());

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Guava // Copy the data from a URL to a file Resources.asByteSource(url).copyTo(Files.asByteSink(file));

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Ease of Use Complexity of Data Amount of Data SharedPreferences Filesystem SQLite

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SQLite

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SQLite • SQL database engine • Good for structured, relational data • A lot of boilerplate

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Real-world uses • Address book • Restaurant ordering system • Product inventory

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public final class PostContract { public PostContract() {} ! public static abstract class Post implements BaseColumns { public static final String TABLE_NAME = "posts"; public static final String COLUMN_NAME_TITLE = "title"; public static final String COLUMN_NAME_AUTHOR_ID = “author_id"; ... } }

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public class PostsDbHelper extends SQLiteOpenHelper { public static final int DATABASE_VERSION = 1; public static final String DATABASE_NAME = "Posts.db"; ! public FeedReaderDbHelper(Context context) { super(context, DATABASE_NAME, null, DATABASE_VERSION); } ! public void onCreate(SQLiteDatabase db) { db.execSQL(SQL_CREATE_ENTRIES); } ! public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { db.execSQL(SQL_DELETE_ENTRIES); onCreate(db); } ! public void onDowngrade(SQLiteDatabase db, int oldVersion, int newVersion) { onUpgrade(db, oldVersion, newVersion); } }

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// Create instance of database helper PostsDbHelper mDbHelper = new PostsDbHelper(getContext());

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// Create instance of database helper PostsDbHelper mDbHelper = new PostsDbHelper(getContext()); ! // Get writable database SQLiteDatabase db = mDbHelper.getWritableDatabase();

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// Create array of columns to retrieve String[] projection = { Post._ID, Post.COLUMN_NAME_TITLE, ... };

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// Create array of columns to retrieve String[] projection = { Post._ID, Post.COLUMN_NAME_TITLE, ... }; ! // Retrieve cursor Cursor c = db.query( Post.TABLE_NAME, projection, selection, selectionArgs, null, // groupBy null, // having null, // orderBy null // limit );

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// Move to first row cursor.moveToFirst();

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// Move to first row cursor.moveToFirst(); ! // Get column index int index = cursor.getColumnIndexOrThrow(Post._ID);

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// Move to first row cursor.moveToFirst(); ! // Get column index int index = cursor.getColumnIndexOrThrow(Post._ID); ! // Get column value long id = cursor.getLong(index);

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// Move to first row cursor.moveToFirst(); ! // Get column index int index = cursor.getColumnIndexOrThrow(Post._ID); ! // Get column value long id = cursor.getLong(index); ! // Close cursor when finished cursor.close();

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// Create instance of ContentValues and set values ContentValues values = new ContentValues(); values.put(Post.COLUMN_NAME_TITLE, title); values.put(Post.COLUMN_NAME_AUTHOR_ID, authorId);

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// Create instance of ContentValues and set values ContentValues values = new ContentValues(); values.put(Post.COLUMN_NAME_TITLE, title); values.put(Post.COLUMN_NAME_AUTHOR_ID, authorId); ! // Insert row using ContentValues long newRowId = db.insert( Post.TABLE_NAME, null, values );

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// Create instance of ContentValues and set values ContentValues values = new ContentValues(); values.put(Post.COLUMN_NAME_AUTHOR_ID, authorId);

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// Create instance of ContentValues and set values ContentValues values = new ContentValues(); values.put(Post.COLUMN_NAME_AUTHOR_ID, authorId); ! // Create selection definition String selection = Post.COLUMN_NAME_AUTHOR_ID + " LIKE ?"; String[] selectionArgs = { String.valueOf(oldAuthorId) };

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// Create instance of ContentValues and set values ContentValues values = new ContentValues(); values.put(Post.COLUMN_NAME_AUTHOR_ID, authorId); ! // Create selection definition String selection = Post.COLUMN_NAME_AUTHOR_ID + " LIKE ?"; String[] selectionArgs = { String.valueOf(oldAuthorId) }; ! // Update rows using ContentValues and selection int count = db.update( Post.TABLE_NAME, values, selection, selectionArgs );

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// Create selection definition String selection = Post.COLUMN_NAME_AUTHOR_ID + " LIKE ?"; String[] selectionArgs = { String.valueOf(authorId) };

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// Create selection definition String selection = Post.COLUMN_NAME_AUTHOR_ID + " LIKE ?"; String[] selectionArgs = { String.valueOf(authorId) }; ! // Delete rows using selection db.delete( Post.TABLE_NAME, selection, selectionArgs );

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Libraries • ActiveAndroid • greenDAO • OrmLite • Sugar ORM

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ActiveAndroid @Table("posts") public class Post extends Model { @Column("title") String mTitle; @Column("author") User mAuthor; ... }

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ActiveAndroid // Query List posts = new Select().from(Post.class).execute();

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ActiveAndroid // Query List posts = new Select().from(Post.class).execute(); ! // Save or update Post post = new Post(); post.setTitle("ActiveAndroid"); post.setAuthor(user); post.save();

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ActiveAndroid // Query List posts = new Select().from(Post.class).execute(); ! // Save or update Post post = new Post(); post.setTitle("ActiveAndroid"); post.setAuthor(user); post.save(); ! // Delete post.delete();

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greenDAO Schema schema = new Schema(1, "de.greenrobot.posts"); ! Entity post = schema.addEntity("post"); post.addIdProperty(); post.addStringProperty("title"); ! Property userIdProperty = user.addLongProperty("author").getProperty(); post.addToOne(user, userIdProperty); ! DaoGenerator daoGenerator = new DaoGenerator(); daoGenerator.generateAll(schema, "../MyProject/src-gen");

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greenDAO // Query List posts = userDao.queryBuilder().list();

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greenDAO // Query List posts = userDao.queryBuilder().list(); ! // Save Post post = new Post(); post.setTitle("greenDAO"); post.setAuthor(user); daoSession.insert(post);

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greenDAO // Query List posts = userDao.queryBuilder().list(); ! // Save Post post = new Post(); post.setTitle("greenDAO"); post.setAuthor(user); daoSession.insert(post); ! // Update post.setModifiedDate(new Date()); daoSession.update(post);

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greenDAO // Query List posts = userDao.queryBuilder().list(); ! // Save Post post = new Post(); post.setTitle("greenDAO"); post.setAuthor(user); daoSession.insert(post); ! // Update post.setModifiedDate(new Date()); daoSession.update(post); ! // Delete daoSession.delete(post);

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OrmLite @DatabaseTable(tableName = "posts") public class Post { @DatabaseField private String title; @DatabaseField private User author; ... }

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OrmLite // Query List posts = postDao.queryForAll();

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OrmLite // Query List posts = postDao.queryForAll(); ! // Save Post post = new Post(); post.setTitle("ORMLite"); post.setAuthor(user); postDao.create(post);

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OrmLite // Query List posts = postDao.queryForAll(); ! // Save Post post = new Post(); post.setTitle("ORMLite"); post.setAuthor(user); postDao.create(post); ! // Update post.setModifiedDate(new Date()); postDao.update(post);

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OrmLite // Query List posts = postDao.queryForAll(); ! // Save Post post = new Post(); post.setTitle("ORMLite"); post.setAuthor(user); postDao.create(post); ! // Update post.setModifiedDate(new Date()); postDao.update(post); ! // Delete postDao.delete(post);

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SugarORM public class Post extends SugarRecord { String title; User author; ... }

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SugarORM // Query List posts = Post.find(Post.class);

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SugarORM // Query List posts = Post.find(Post.class); ! // Save or update Post post = new Post(); post.setTitle("SugarORM"); post.setAuthor(user); SugarRecord.save(post);

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SugarORM // Query List posts = Post.find(Post.class); ! // Save or update Post post = new Post(); post.setTitle("SugarORM"); post.setAuthor(user); SugarRecord.save(post); ! // Delete SugarRecord.delete(post);

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A note about ORMs

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Ease of Use Complexity of Data Amount of Data SharedPreferences Filesystem SQLite

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Network

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Network • File sync or mobile backend • Cross-device storage • Many storage options • Not always available

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Sync Libraries • Box • Dropbox Sync • Google Drive • OneDrive

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MBaaS Libraries • BaasBox • Helios • DropBox Datastore • Kinvey • Parse

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BaasBox • Administration console • Users management • Content management • File management • “Friendship” • DB management • Push notifications • API access management

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Helios • Data synchronization • Push notifications • In-App purchases • Logging and Analytics • Passbook & Newsstand (iOS)

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Dropbox Datastore • Cloud datastore • Local datastores • Shared datastores • Push notifications

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Kinvey • Cloud datastore • Local datastore • User management • File management • Push notifications • Location content • Backend services • Encryption • External data sources

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Parse • Cloud datastore • Local datastore • Social integration • Push notifications • Analytics

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NoSQL

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NoSQL • Key value pairs or documents • Simple design • Non-relational • Implementations vary

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Libraries • Couchbase Lite • JasDB • SimpleNoSQL • SnappyDB • WaspDB

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Couchbase Lite • JSON document store • Full query API • Server and peer-to-peer replication

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JasDB • JSON document store • Full query API • REST and native APIs

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SimpleNoSQL • JSON document store • Lightweight functional queries • Backed by SQLite

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SnappyDB • Key value store • Use primitive type and array values • Based on Google’s LevelDB • Uses Snappy compression and Kryo serialization

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WaspDB • Key value store • Use complex key and value types • Uses Kryo serialization

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Easy to use Complex data A lot of data Distributed SharedPreferences Filesystem SQLite Network NoSQL

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Questions? @pardom