There's an existing bug for this. I'm not sure how fixable it's going
to be; welcome to the implementation nitty gritty of generic types and
type erasure. Just cause you don't see the typecasts doesn't mean the
compiler has put them there.
Here's a challenge: what if there was a createWidget() method on your
class. How would you implement it, to create an instance of the
correct class? You can't do a new T() (the compiler won't let you,
since it doesn't know what T is).
On 6/25/07, Bill Holloway <[EMAIL PROTECTED]> wrote:
I have a Widget base entity extended by several concrete product
entities. I have
public class <T extends Widget> EditWidgetPage
{
...
@Persist
public Long _someWidgetId;
public T _someWidget;
// normal setters / getters
void onActivate (long id)
{
_someWidgetId = id;
_someWidget = _dao.get (id); // gets right subtype of Widget.
Generics. Tested.
}
// onPassivate as per usual pattern.
void onActionFromEditForm ()
{
_dao.saveOrUpdate (_someWidget);
}
}
The page for this just uses a bean edit form, nothing else:
object="someWidget". The saveOrUpdate call complains that someWidget
is of type Widget rather than the subclass it's instantiated to be.
Any thoughts?
bill
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Howard M. Lewis Ship
TWD Consulting, Inc.
Independent J2EE / Open-Source Java Consultant
Creator and PMC Chair, Apache Tapestry
Creator, Apache HiveMind
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