Sunday, August 24, 2014

Transactional Data Caching for ADF Mobile MAF Application

I have described basic idea for data caching in ADF Mobile MAF application in my previous post - Data Caching Implementation for ADF Mobile MAF Application. Today I would like to extend similar solution to handle transactional data caching. Sample application displays list of tasks, user can update task status and description. These updates will be saved locally, until the next synchronisation time with the server.

Updated sample application with MAF mobile and server side implementations can be downloaded from here - User could select a task on his mobile device:

Update task status and description, these changes are stored locally in SQLite DB, no extra call is done to the Web Service at this time:

Changes for multiple tasks can be synchronised in batch. User could go and change different task without submitting previous changes to the Web Service, update task status:

Finally when user decided to synchronise his changes with the Web Service, he could use refresh option:

When synchronisation happens, we can see activity in the server side log. ADF BC executes update operation for submitted task, update for the first task:

Next is called update for the second task:

MAF task flow is updated for this use case, and is based on the task flow from application described in the previous post. We are not calling Web Service from the task flow method call anymore, this call is done programmatically, during refresh:

Web Service method in ADF BC is updated to check if row exists - if yes, data is updated. If row doesn't exist - no error is thrown, task list will be refreshed and latest changes will be displayed to the user on the mobile device. In the real application, you may inform user about the missing task:

Custom method is exposed as ADF BC Web Service method:

To understand how sample application works on MAF mobile side, we should refer to the task flow diagram. Edited changes are submitted to the local SQLite DB through updateTaskLocal method call. This call invokes Java method, where changes are stored locally in the list of tasks. In addition, record about latest task changes is stored in special table with change history:

We are checking in the change history, if the same task was already updated - if no, we are simply storing task ID. This would allow later during synchronisation to retrieve changed task details and update task first through Web Service, before fetching data. If task was already updated, there is no need to insert task ID again:

During data synchronisation, we are checking if there are any rows changed and stored locally. Only after this check is completed, task list data is refreshed and loaded from Web Service:

Changes for each updated task are synchronized through Web Service. Firstly, task ID is retrieved from changes history table. Using this ID, actual changed are fetched from SQLite DB and sent over Web Service to the server side ADF BC for update. Once all the changes are synchronised, local changes history is cleared:

Web Service call to update data through ADF BC is done programmatically, using MAF mobile helper class AdfmfJavaUtilities. We are constructing list of parameters with names, values and types - invoked method even doesn't need to be defined in the Page Definition, it will be referenced directly from the bindings:


Шеремета Сергей said...

Hello, Andrejus!
Great article, thank you!

But i think there are small error in method initializeDatabaseFromScript of LifeCycleListenerImpl class.
Correct code must be like this (union commit() and close() in brackets):

finally {
if (conn != null) {

by piece of code
if (dbFile.exists()) return;

we will trying to close conn object without initialisation.

Andrej Baranovskij said...

Thanks for update, I will double check this.


Rakesh said...

Great Post, Thank You very much.

Is there any way to synchronize the data automatically when ever network status is changed, even though if I close the application from mobile???