This document discusses implementing a transaction manager in a rich internet application (RIA) to allow undoing and redoing of actions. It describes the history of client-server and web applications. It then explains how RIAs are more sophisticated and may require plugins but allow for easy client-side execution. The document outlines some RIA frameworks and then describes how a transaction manager could track complex interactions in a RIA by backing up actions in case of a mistake. It provides details on creating a simple sample application to demonstrate the transaction manager including using design patterns like singleton and command patterns. The transaction manager class is shown which manages undo and redo stacks and dispatches events. The document concludes with discussing advanced features and taking questions.

1. Ctrl-Z to Undo: Implementing a Transaction Manager in a Rich Internet ApplicationGalen Rileygalenriley@gmail.com@TotallyGreatBarCamp Chattanooga 2009

2. AgendaHistory of network applicationsDiscuss advantages of RIAsDescribe a transaction managerWrite a simple applicationImplement the transaction manager

3. Client-Server ApplicationsClient-Server ApplicationsInstalled on each machineCustom network programmingUpdates on the server may require updates on each client

4. Web ApplicationsExist entirely on a serverWork in a browser – no installation!Easily managed and modified

5. Rich Internet ApplicationsMore sophisticatedMay require a browser plug-inConsistency across browsersEasy to do client-side executionMedia

6. RIA FrameworksAdobe FlexMicrosoft SiverlightJavaFXAJAX

7. Transaction ManagerComplex interactions in a RIABack up in case of a mistakeRIA development lends itself to adding this feature

8. A Simple Application

9. A Simple Application

10. ChecklistStack data structure available anywhere in the program

11. Singleton Pattern

12. Using a SingletonTransactionManager.getInstance().doSomething()

13. ChecklistStack data structure available anywhere in the programClasses to hold state informationCommand design pattern

14. Transaction Class

15. ChecklistStack data structure available anywhere in the programClasses to hold state informationCommand design patternMethod of passing messages

16. TransactionManager classprivatevar _undoStack:Array;privatevar _redoStack:Array;publicfunction addTransaction( transaction:Transaction ) :voidpublic function undo() :voidpublic function redo() :voidDispatch events from here

17. Using the Transaction ManagerSelect interesting user actionsAdd Transaction objects to the managerListen for TransactionEvent.UNDO and TransactionEvent.REDOUse the Transaction object to roll back the actionAllow the user to Undo and Redo

18. One Last ThingUndoing an action runs code that modifies the TransactionManager’s stackSolution: Ignore transactions while executing a Undoprivatevar _ignoreOutsideTransactions:Boolean;privatefunction ignoreOutsideUndoTransactions() :voidprivatefunction resumeOutsideUndoTransactions() :void

19. Advanced FeaturesMultiple levels of undoprivatestaticconst TRANSACTION_LIMIT:int = 10;Batch transactionsBetter UI Integration

20. Questions?Source code for the transaction manager and sample application are available. Email galenriley@gmail.com