Batch mode & ClassCastException question

Question

Hi
I'm using JDev 10.1.2.1 (1913) and have a problem with a JClient app using batch mode.
The issue started when I decided to use ranges on my JTable. In sync=Immediate mode the JTable would render with data equaling the number of records requested from my VO plus empty rows (my NextSet and PrevousSet operation buttons made sets appear and disappear in existing rows of the table). For example, picture a table with 100 records and a VO tuned to request in batches of 10. My JTable would render with 10 rows displayed and 90 empty rows. When I click NextSet, the first 10 rows go blank and the next 10 appear. Obviously this is not desired behavior.
Ok, so I decided to try "Batch" mode which cause the jTable to operate correctly but it causes ClassCastException errors when calling custom VO methods. Since I make sure to cast to interfaces and not implementations (per Steve's article: http://www.oracle.com/technology/products/jdev/tips/muench/batchmode/index.html) I don't understand why I'm getting these.
Here's a test case to demonstrate:
1) New Project - Connection: SCOTT
2) Create EmpVO - Select * from EMP
3) Tune EmpVO - Batches of 5, as needed; Fill Last Page unchecked
4) Edit EmpVO class. Create custom method
public String toString()
return "Custom method: " + getClass().toString();
5) Shuttle method to selected for Client Interface (interface EmpVO generated and automatically implemented by EmpVOImpl)
6) Create EmpAppMod - Assign EmpVO
7) Create runnable Panel from VO (Swing/JClient for ADF; template=Table)
8) Modify panel by adding new panel (Constraints = SOUTH) and dragging "NextSet" and "PreviousSet" Operations from the EmpVO1 data control onto new panel as buttons
9) Under the panel's UIModel you'll see two iterators for the same VO (one for the jTable and one for the buttons). Check the range sizes, the table iterator should be set to -1 and the button iterator to 5 (matches the VO's batch retrieve section).
10) Edit panel code and add a call to the custom VO method in main():
System.out.println(((EmpVO)panel.getPanelBinding().findIterBinding("EmpVO1Iter").getViewObject()).toString());
11) Set Sync=Immediate for the AppMod DC in DataBindings.cpx
12) Run panel
Hopefully you'll see the blank row behavior described above and the custom toString() result printed to the console.
Again, if batch mode works I don't care about this jTable problem.
Now set Sync=Batch and re-run the panel. In my version the jTable works as expected but I get the ClassCastException...even though I'm casting to the EmpVO interface. In my real application this means I can't call any of my custom VO methods.
Exception:
Exception in thread main
java.lang.ClassCastException: oracle.jbo.common.ws.WSViewObjectImpl
     at mypackage9.PanelEmpVO1.main(PanelEmpVO1.java:95)
If anyone has a suggestion on how to make this work (in either sync mode) pls let me know.
thanks
John

Answer 1

thanks but I don't understand. I thought I was using the client interface. The call to oracle.jbo.common.ws.WSViewObjectImpl is not being done by me.
I found another thread (Re: ClassCastException: WSViewObjectImpl where Steve M. says do access the VO interface in batch mode like so:
ApplicationModule am = (ApplicationModule) actionContext.getBindingContext().findDataControl("YourDataControlName").getDataProvider();
YourCustomViewObject vo = (YourCustomViewObject) am.findViewObject("view1");
I'm using a JClient panel to call the custom method so my code is:
ApplicationModule am = (ApplicationModule)panel.getPanelBinding().getBindingContext().findDataControl("EmpAMDataControl1").getDataProvider();
EmpVO ep = (EmpVO)am.findViewObject("EmpVO1");
ep.toString();
Both the default ApplicationModule and custom EmpVO are interfaces but I still get the ClassCastException
I don't know if this helps, but if I create a method in my AppMod that calls the custom VO method I don't get the error....but that can't be right - I shouldn't have to create AppMod methods for all custom VO methods. Obviously I missing something fundamental