Clearing VO dynamic Query-By-Example ViewCriteria

Question

Looking for some help with JDev 11.1.1.4.0, ADF BC + ADF Faces RC please.
At it's simplest we're looking how to clear the query-by-example (QBE) filters on a VO without using the table UI component and not accidentally clearing other view criteria on the VO. To explain our use case first let me define the characteristics of our app. We have:
a) A BTF based on fragments:
a.1) The transaction/data control scope = Use Existing Transaction if Possible/Shared
a.2) It contains a single fragment
a.3) The fragment contains a table based on an ADF BC View Object (VO)
a.4) The VO has a view criteria defined at design time, implemented via the Application Module (AM)
a.5) The table allows the user to filter the data
a.6) The BTF does not include any task flow returns or parent actions
b) A consuming BTF based on pages:
b.1) The transaction/data control scope = Always Begin New Transaction/Isolated
b.2) It contains 2 pages with navigation rules to move between them (back/forward)
b.3) The fragment from "a" is included on both pages in "b"
b.4) When navigation occurs between the pages, it is invoked via buttons in this BTF, not the original BTF via parent actions or task flow returns. This aligns with point a.6. As such when navigations occurs between the 2 pages, the region/task flow binding instance of "a" in the region of the current page of "b" is prematurely terminated. The implication is the instance of "a" doesn't get a chance to do any processing before it is closed.
Note that "a" and "b" are built in isolation of each other. "b" has no inherit knowledge about the components of "a" nor the ADF BC components. The implication is "b" cannot attempt to grab the table UI component, nor manipulate the ADF BC components as it doesn't know anything about the BTFs dropped on its pages.
If the user opens the 1st page in "b" and enters a query-by-example criteria on the table from the region containing the 1st of instance of "a", then the user navigates to the 2nd page, the filter criteria are still set on the 2nd instance of "a". This is expected behaviour as "a" has data control scope = shared implying when the QBE criteria are set on page 1, they are written down to the VO, which when the user navigates to page 2, as it is sharing the same VO the QBE criteria are there to reuse/share on page 2.
In our scenario what we want to do:
1) Is in navigating between the 2 pages, we wish the query-by-example filter criteria to be cleared/reset, such that navigating between pages the filter criteria are empty/fresh
2) However in navigating between the pages we must not lose the design time view criteria (and it's bind variable value) that has already been applied
3) Maintain shared data control scope so we minimize the amount of database connections
The common solution to clearing the QBE filter is as per Timo Hahn's following blog entry: http://tompeez.wordpress.com/2011/10/29/jdev-how-to-reset-a-filter-on-an-aftable/
Yet that solution assumes the code has access to the table UI component. As we need the QBE criteria reset on navigation caused by "b", and such navigation causes a premature termination of "a" there's no chance for "a" to grab the table component and clear the filter criteria before "b" navigates away. The logical solution to this is on entering "a" again, to programatically reset the QBE criteria as part of the initial steps in the "a" BTF. But on entering "a" using Timo's solution, the method call doesn't have access to table UI component as the fragment isn't yet rendered, making this solution not viable.
Another solution we've tried is calling applyViewCriteria(null) then reapplying our view criteria from a VO client interface method, but it appears we aren't clearing the QBE criteria. This worries me a bit because it looks like you can't discern the QBE view criteria from the normal view criteria unless you go through the table UI component methods.
So how do we clear the QBE filter criteria programatically, without clearing (or at least restoring) the design time view criteria, and without relying on the table UI component to clear the QBE criteria?
Phew, I hope that makes sense? Thanks for your help in advance.
CM.
PS. There is an assumption in the title of my post that table Query By Example criteria are stored as ADF BC View Object view criteria. Possibly it's a separate mechanism so please be careful this doesn't lead you astray in answering my post.

Answer 1

Chris,
I don't have time to follow this through right now, but I'm on to something.
I was able to affect the filter via the binding container (at least it's not the UI). See this code:
  public void a(ActionEvent e)
   String s = "#{bindings.EmployeesView1Query.queryDescriptor}";
   Object o = JSFUtils.resolveExpression(s);
   FilterableQueryDescriptor f = (FilterableQueryDescriptor) o;
   f.removeCriterion(f.getCurrentCriterion());
  }Now, it doesn't do exactly what you want (it actually somehow makes no rows show up in the table), but I believe it's moving in the right direction.
Am leaving for the office (5:40 am), so I'll pass this over to you to have a gander.
John