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From David Beer <david.m.b...@btinternet.com>
Subject Re: Understanding getResultList()
Date Tue, 22 Jan 2008 10:55:38 GMT
Hi Patrick

I will be able to get the exact information retruned later when I am back home. 

I am trying to display a list of the items returned from the query in a JList (javax.swing.JList).
A JList takes either an array, a ListModel or a Vector; I was trying to use a Vectory as I
can just add elements to it and not worry about memory allocation or the size of the Vector
being too large.

My point is that when I tried to cast the resulting data from the query I got an exception.
Cannot Cast Delegate org.apache.openjpa

I will get the exact data this evening when i get home 

Thanks

David

----- Original Message ----
From: Patrick Linskey <plinskey@gmail.com>
To: users@openjpa.apache.org; david.m.beer@btinternet.com
Sent: Monday, 21 January, 2008 11:52:15 PM
Subject: Re: Understanding getResultList()

Hi,

> and in return I am seeing a list containing a delegate and a
> persistence object.

Can you include a printout of the data you see, or some more detailed
explanation, such as class names of the instances returned?

> display. This is fine with a small amount of records but what about a
> large amount of records.

Are you concerned about the overhead involved in iterating through a
result list fully just to copy it over to the Vector? If the framework
that you are using does not provide any interface-based support, then
you might not have many options. One idea might be to try to create a
subclass of Vector that overrides most methods to just return values
from the actual backing list.

-Patrick

On Jan 21, 2008 3:34 PM, David Beer <david.m.beer@btinternet.com>
 wrote:
> Hi All
>
> I have a n issue with using Query getResultList(), I am executing a
> nativeQuery("SELECT * FROM ENTRY", Entry.class). And performing the
> query like so List<Entry> results =
 (List<Entry>)query.getResultList();
> and in return I am seeing a list containing a delegate and a
> persistence object.
>
> My main problem is that I am trying to display the resulting data
 that
> comes back in a JList, in order to set the list data on a JList you
 have
> to have the data in a Vector. So when I tried to cast the  List to a
> Vector I got an exception.
>
> When I perform the same query using TopLink I get back a list of
 Objects
> of the type and no extra information. At the moment I am going
 through
> the results and getting each Object element and adding to Vector to
> display. This is fine with a small amount of records but what about a
> large amount of records.
>
> What is the best way of getting back just a list of Objects no
> additional data?
>
> Thanks
>
> David
>



-- 
Patrick Linskey
202 669 5907




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