Introduction to SQLite in Adobe AIR

Introduction to SQLite
in Adobe AIR
Peter Elst - Flash Platform Consultant

Why SQLite in Adobe AIR?
■ Embedded SQL Database Engine

■ Implements most of SQL92

■ Light-weight, cross-platform, open source

■ No setup, conﬁguration or server required

■ Each database is contained within a single ﬁle

How do you use it?
1. Create a File reference

2. Create an instance of ﬂash.data.SQLConnection and
ﬂash.data.SQLStatement

3. Open the database connection

4. Specify the connection and SQL query to run

5. Run SQLStatement.execute()

How do you use it?
import flash.filesystem.File;
import flash.data.*;

var dbFile:File =
File.applicationStorageDirectory.resolvePath("contacts.db");

var sqlConn:SQLConnection = new SQLConnection();
var sqlStatement:SQLStatement = new SQLStatement();

sqlConn.open(dbFile);

sqlStatement.sqlConnection = sqlConn;
sqlStatement.text = "SELECT * FROM contacts";
sqlStatement.execute();

var result:Array = sqlStatement.getResult().data;

Synchronous versus Asynchronous
■ Synchronous - blocks application until result is available


var result:SQLResult = sqlConn.getResult().result;

■ Asynchronous - uses events and event listeners


sqlConn.addEventListener(SQLResultEvent.RESULT, onSQLResult);
sqlConn.addEventListener(SQLResultEvent.ERROR, onSQLError);

sqlConn.openAsync(dbFile);

ﬂash.data.SQLConnection
■ Connects to the database ﬁle

■ Provides events for asynchronous use

■ Schema access

ﬂash.data.SQLStatement
■ Executes a SQL query on the speciﬁed database connection

■ Provides events for asynchronous use

■ Supports result paging

ﬂash.data.SQLMode
■ SQLMode.CREATE (default)

■ open connection and create database if it doesn’t exist

■ SQLMode.READ

■ open connection as read only

■ SQLMode.UPDATE

■ open connection, don’t create database if it doesn’t exist

Storage types
■ NULL - NULL value (null)

■ INTEGER - signed integer (int)

■ REAL - ﬂoating point (Number)

■ TEXT - UTF16 text string (String)

■ BLOB - blob of data (ByteArray)

AIR specific column affinities
■ String - String value (equivalent to TEXT)

■ Number - floating point number (equivalent to REAL)

■ Boolean - Boolean class

■ Date - Date class

■ XML - XML class

■ XMLList - XMLList class

■ Object - Object class

SQLStatement Parameters
■ The parameters feature protects your SQL statements from
SQL injection

sqlStatement.text = "SELECT * FROM contacts WHERE id = @ID";
sqlStatement.parameters["@ID"] = someVariable;

■ You can use the @ or : symbol to denote a parameter to be
replaced, works both string based as index based

sqlStatement.parameters[0] = someVariable;

Result Paging
■ Paging allows you to limit the amount of rows you get
returned when doing a select operation

sqlStatement.text = "SELECT * FROM contacts";
sqlStatement.execute(10);

■ You can get the next batch of rows returned by calling the
next method on the SQLStatement instance

sqlStatement.next();

ﬂash.data.SQLResult
■ SQLResult.data - array of objects for each row of the result

■ SQLResult.complete - returns a boolean indicating whether
or not the full result was shown

■ SQLResult.lastInsertRowID - return id for the last row that
was inserted

■ SQLResult.rowsAffected - number of rows affected by an
insert, update or delete operation

Transactions
■ Transactions allow multiple SQL statements to run within one
write operation to the database

■ Much more optimized way of handling large insert operations,
allows rollback of the complete transaction if an error occurs

sqlStatement.text = "INSERT into contacts VALUES (@NAME, @EMAIL)";

sqlConn.begin();
for(var i:uint=0; i<contacts.length; i++) {
sqlStatement.parameters["@NAME"] = contacts[i].name;
sqlStatement.parameters["@EMAIL"] = contacts[i].email;
}
sqlConn.commit();

Database Schema
■ Allows you to introspect tables, views, columns, indices, triggers


sqlConn.loadSchema();
var result:SQLSchemaResult = sqlConn.getSchemaResult();

var table:SQLTableSchema = result.tables[0];
var column:SQLColumnSchema = table.columns[0];

trace(column.name);
// returns name of the first column in the first table

Database encryption
■ New feature in AIR 1.5
■ Password protect database ﬁles

var encryptionKey:ByteArray = new ByteArray();
encryptionKey.writeUTFBytes("notverysecretpassword");

sqlConn.open(dbFile,SQLMode.READ,null,false,1024,encryptionKey);

Encryption best practices
■ Do not embed passwords in your application!

■ com.adobe.air.crypto.EncryptionKeyGenerator
■ Secure solution: creates random salt and stores in the
EncryptedLocalStore (linked to user and machine)
■ Prevents dictionary attack

■ com.dehats.air.sqlite.SimpleEncryptionKeyGenerator
■ Less secure but allows access by other users and other
applications, doesn’t generate a random salt value.

http://bit.ly/SimpleEncryptionKeyGenerator

Database synchronization
■ Synchronize database between server and client(s)
■ Some different strategies
■ overwrite (server overwrites client)
■ check what to synchronize
■ timestamp field
■ field by field comparison
■ dirty flag

■ LiveCycle Data Services has built-in SQLite synchronization
support including offline caching and conflict management.

Lita - SQLite database administration

DAO-Ext - value object generator

What is DAO?
■ Data Access Objects - abstract interface to a database
■ implements common features (select, update, delete, ...)
■ Uses value objects (VO)

What is DAO?
■ Data Access Objects - abstract interface to a database
■ implements common features (select, update, delete, ...)
■ Uses value objects (VO)

■ Value Objects (also known as Data Transfer Objects)
■ don’t implement any behavior
■ encapsulates properties through getter/setter methods
■ represent an entry in a database table

Example VO
public class contactsVO {

private var _name:String;

public function get name():String {
return _name;
}

public function set name(value:String):void {
_name = value;
}

...

}

Example DAO
public class contactsDAO {

public function insertRow(rowItem:contactsVO):void {
...
}

public function updateRow(rowItem:contactsVO):void {
...
}
public function deleteRow(rowItem:contactsVO):void {
...
}

}

SQLite wrapper classes
■ Simple way to use SQLite features in your application
■ ActionScript 3.0 classes, primarily for use as tags in MXML

<sql:SQLite id="myDB" file="contacts.db" open="myQuery.execute()" />

<sql:Query id="myQuery" connection="{myDB.connection}"
sql="SELECT * FROM contacts" />

<mx:DataGrid id="myDataGrid" dataProvider="{myQuery.data}" />
<mx:Button label="Refresh data" click="myQuery.execute()" />

SQLite wrapper - SQLite class
■ Properties
■ ﬁle - name of database ﬁle
■ connection - returns SQLConnection instance

■ Methods
■ open - create database connection
■ close - close database connection

■ Events
■ open - database connection is opened
■ close - database connection is closed
■ error - error connecting to database

SQLite wrapper - Query class
■ Properties
■ connection - reference to SQLConnection
■ sql - String value of SQL statement
■ parameters - parameters for SQL statement
■ data - result returned from query

■ Methods
■ execute - run query on database

■ Events
■ result - result received from query
■ error - error executing query

Resources
■ Lita - SQLite Administration Tool by David Deraedt
www.dehats.com/drupal/?q=node/58

■ DAO-Ext by Comtaste
code.google.com/p/dao-ext/

■ Adobe AIR Developer Center
www.adobe.com/devnet/air/

■ Adobe AIR Marketplace
www.adobe.com/go/airmarketplace

Thanks for your time
Any questions or feedback - feel free to get in touch!

blog www.peterelst.com
email info@peterelst.com
twitter @peterelst

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Introduction to SQLite in Adobe AIR

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