[JClient 9.0.3] Trapping events and canceling actions

Question

Subject: [JClient 9.0.3] Trapping events and canceling actions
I'd like to be able to, based on some condition, abort certain
actions (navigate, delete, insert, etc, etc) when the appropriate
events have been fired.
E.g., in case the Transaction is dirty and when I navigate to a
certain row in a certain ViewObject instance, I would like to
intercept this action and let the user decide what to do:
Commit/Rollback/Cancel. Of cource when 'Cancel' is selected, the
navigation-action should be aborted at all.
I have realised this functionality by subclassing JUNavigationBar
and either calling super's actionPerformed() or not. This works
perfectly, but of course there are other means to navigate (a
JComboBox + NavigationBinding, a JTable or programmatically), so
I would need to implement similar functionality for each of these
component types.
So, what I need to do is to intercept these actions on a lower
level. It appears that I need to register RowSetListeners to
ViewObject instances, but as far as I can tell, this way there
isn't a real way to abort these actions once they are started.
Am I pherhaps overlooking something? Any help and/or suggestions
would be greatly appreciated.
Arno

Answer 1

Subject: [JClient 9.0.3] Trapping events and canceling actions
I'd like to be able to, based on some condition, abort certain
actions (navigate, delete, insert, etc, etc) when the appropriate
events have been fired.
E.g., in case the Transaction is dirty and when I navigate to a
certain row in a certain ViewObject instance, I would like to
intercept this action and let the user decide what to do:
Commit/Rollback/Cancel. Of cource when 'Cancel' is selected, the
navigation-action should be aborted at all.
I have realised this functionality by subclassing JUNavigationBar
and either calling super's actionPerformed() or not. This works
perfectly, but of course there are other means to navigate (a
JComboBox + NavigationBinding, a JTable or programmatically), so
I would need to implement similar functionality for each of these
component types.
So, what I need to do is to intercept these actions on a lower
level. It appears that I need to register RowSetListeners to
ViewObject instances, but as far as I can tell, this way there
isn't a real way to abort these actions once they are started.
Am I pherhaps overlooking something? Any help and/or suggestions
would be greatly appreciated.Yes you're right in saying that there are many ways one could perform navigate - by other controls, by calling next() on the VO or even on the RowSetIterator. Also BC4J does not generate 'events' before navigation to preempt navigation unless a row is 'modified' in which case RowValidation events are generated for the Entities modified in that row.
The most generic way you may fix this is by 'listening' to rowsetiterator's navigation events and get the PreviousRow from the navigation events and set focus back to it if user presses cancel, or get the current RowKey and let the user commit/rollback and then restore the currency to a row with that rowkey (just in case the MT is set to clear all caches on commit/rollback transaction boundaries). Note that insert/delete events should not be handled this way as those event points are usually generated due to a button action and it's easier to preempt these actions rather than 'let the actions' complete and then perform a rollback-to-a-particular-point.
Arno