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From Tomas Stenlund <>
Subject Re: ToManyList cannot be instantiated with a list.getClass().newInstance()
Date Thu, 26 Jul 2012 07:31:10 GMT
Hi Andrus,

thanks for taking your time to give your opinion.

Yes, I have come to the same conclusion as you. The TooMany list outside 
cayenne don't really mean anything. Since Pivot is able to swallow 
List:s right out of the box to display them in List-, Tablewiddgets etc. 
I got led down the wrong alley. Looking into the source of Pivot it 
actually does some manipulating with the List and creation of new Lists 
that will not work with cayenne. I have also discussed this with the 
guys at the Pivot  list.

So, now I convert the Cayenne TooManyList to simple "Java lists" and 
send them into Pivot instead. So when the Pivot dialogues want to change 
some data in the CayenneObjects it goes through getters/setters I can 
just then commit the changes after the user for instance press "Save". 
So it works well.



PS ! Have a look at the application at, a cross country skiing time 
recording and competition management application using Apache Pivot and 
Cayenne. It is a pleasure working with those two frameworks, among 
other. DS!

On 07/23/2012 03:39 PM, Andrus Adamchik wrote:
> Not familiar with Pivot, so not sure what its expectations are. But creating a ToManyList
outside Cayenne generally doesn't seem like a good idea. Maybe what you doing as a workaround
is perfectly valid. So what is the purpose of creating a new list by Pivot and what happens
to that list after that? Is there an attempt to persist it afterwords?
> Cheers,
> Andrus
> On Jul 12, 2012, at 8:46 AM, Tomas Stenlund wrote:
>> Hi,
>> I'm using Cayenne 3.1B1 and Pivot 2.0.2 as a GUI and have come across something which
I would gladly have some good suggestions around.
>> The automatically generated getters for the relationships sometimes returns a ToManyList
of objects. To be able to use that list directly in Pivot:s widgets I have to wrap it with
a ListAdapter. So, now for the cayenne questions, it seems that ToManyList does not have an
empty constructor (maybe it does not have one because it does not really mean anything in
the ToMany relationship) causing a call to the list.getClass().newInstance() that the ListAdapter
in pivot does to create a new empty list of the same type to throw the InstantiationException.
>> It might be that the ListAdapter is wrongly implemented to assume that the List:s
always have an empty constructor or something else. Any ideas ? For now I just create a new
list (ArrayList or something similar) and fills it up with the objects in the ToManyList to
send it into Pivot to make it work, but it does seem to give an ugly solution moving from
one list type to another just to come around this.
>> Thanks for any comments,
>> Cheers,
>> Tomas

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