Vineet , Yes, this is a technique that, carefully and properly used, could help in building a generic DAO. Can you elaborate on "intializing the class type in constructor." ?
Regards - Cemal jWeekend OO & Java Technologies, Wicket Training and Development http://jWeekend.com vineet semwal wrote: > > the first time I used genericsuperclass() was in generic daos after > reading https://www.hibernate.org/328.html, > though it has it's own quirks, it doesn't apply every where .. > abstract modifier in above code was needed,it's done so that one will > eventually subclass funnyfactory > and that genericsuperclass hack will work .. > > apart from that one another simple way for retrieving the generic > classtype > is intializing the class type in > constructor. > > conditions apply ;) > -- > regards, > Vineet Semwal > > > On Thu, Sep 17, 2009 at 4:13 AM, jWeekend > <[email protected]>wrote: > >> Since you can NOT do >> >> class S<T>{S(){T t = new T();}} // broken >> >> how would you create an object of type T somewhere in S? Think about this >> before you read on ... >> >> At the risk of reigniting the world-famous generics debates of >> yesteryear, >> just as our noble core-developers regroup to start work on making 1.5 >> even >> better than what is already the best Java web framework, I thought I'd >> share >> the idea I suggested to one of our developers who was having a bad day >> with >> generics (for several good reasons [1][2]) a couple of months ago, in >> case >> you can make use of it somewhere, or, find an even more convoluted >> solution >> - notice the innocent looking abstract modifier! >> // not real code >> // don't try this at home without adult supervision! >> public abstract class FunnyFactory<T> { >> private T instance = null; >> public T getInstance() { >> if (instance == null) { >> try { >> final ParameterizedType gsc = >> (ParameterizedType)getClass().getGenericSuperclass(); >> final Class<T> typeT = (Class<T>) >> gsc.getActualTypeArguments()[0]; >> instance = typeT.newInstance(); >> } catch (InstantiationException e) { >> e.printStackTrace(); >> } catch (IllegalAccessException e) { >> e.printStackTrace(); >> } >> } >> return instance; } >> } >> >> ... >> >> public class CreateInstanceOfTypeParameter { >> @Test >> public void testCreateInstanceOfTypeParameter() { >> FunnyFactory<Point> factory = new FunnyFactory<Point>() {}; >> factory .getInstance().x = 22; >> factory .getInstance().y = 47; >> assertEquals(new Point(22, 47), factory.getInstance()); >> } >> } >> >> Regards - Cemal jWeekend OO & Java Technologies, Wicket Training and >> Development http://jWeekend.com >> >> [1] http://gafter.blogspot.com/2006/11/reified-generics-for-java.html >> [2] >> http://weblogs.java.net/blog/arnold/archive/2005/06/generics_consid_1.html >> >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: [email protected] >> For additional commands, e-mail: [email protected] >> >> > > -- View this message in context: http://www.nabble.com/-OT--More-%22Java%27s-generic-type-parameters-are-not-reified%22...-tp25482235p25487989.html Sent from the Wicket - User mailing list archive at Nabble.com. --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
