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Class<T> get generic type at runtime CDI

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  Class<T> get generic type at runtime CDI Leonan Luppi <leonan.luppi@gmail.com> - 2014-12-19 04:23 -0800
    Re: Class<T> get generic type at runtime CDI Robert Klemme <shortcutter@googlemail.com> - 2014-12-19 15:29 +0100
      Re: Class<T> get generic type at runtime CDI Leonan Luppi <leonan.luppi@gmail.com> - 2014-12-19 07:13 -0800
        Re: Class<T> get generic type at runtime CDI Sebastian <news@seyweiler.dyndns.org> - 2014-12-20 15:20 +0100
    Re: Class<T> get generic type at runtime CDI Andreas Leitgeb <avl@auth.logic.tuwien.ac.at> - 2014-12-20 18:28 +0000

#30594 — Class<T> get generic type at runtime CDI

Hello,

I'm try to get generic class type but isn't work. Someone can help me? I'm using CDI Weld to Inject my DAO class with a generic type:


@Inject
private DAO<Agent> dao;

And my DAO Class:

public class DAO<T> {
	
public T findAll() {
	CriteriaQuery<T> query = em.getCriteriaBuilder()
								 .createQuery(HERE_MY_GENERIC_CLASS);
	query.select(query.from(HERE_MY_GENERIC_CLASS));
	return (T) em.createQuery(query).getResultList(); 	
}
	
}


How can i get at runtime? To make a query.

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#30595

On 19.12.2014 13:23, Leonan Luppi wrote:
> Hello,
>
> I'm try to get generic class type but isn't work. Someone can help
> me?  I'm using CDI Weld to Inject my DAO class with a generic type:
>
>
> @Inject
> private DAO<Agent> dao;
>
> And my DAO Class:
>
> public class DAO<T> {
> 	
> public T findAll() {
> 	CriteriaQuery<T> query = em.getCriteriaBuilder()
> 								 .createQuery(HERE_MY_GENERIC_CLASS);
> 	query.select(query.from(HERE_MY_GENERIC_CLASS));
> 	return (T) em.createQuery(query).getResultList(); 	
> }
> 	
> }
>
>
> How can i get at runtime? To make a query.

Judging from the code you presented you need at least to return a 
collection of T (e.g. Iterable<T>) and not a T.

Cheers

	robert


-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/

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#30597

Em sexta-feira, 19 de dezembro de 2014 12h30min14s UTC-2, Robert Klemme  escreveu:
> On 19.12.2014 13:23, Leonan Luppi wrote:
> > Hello,
> >
> > I'm try to get generic class type but isn't work. Someone can help
> > me?  I'm using CDI Weld to Inject my DAO class with a generic type:
> >
> >
> > @Inject
> > private DAO<Agent> dao;
> >
> > And my DAO Class:
> >
> > public class DAO<T> {
> > 	
> > public T findAll() {
> > 	CriteriaQuery<T> query = em.getCriteriaBuilder()
> > 								 .createQuery(HERE_MY_GENERIC_CLASS);
> > 	query.select(query.from(HERE_MY_GENERIC_CLASS));
> > 	return (T) em.createQuery(query).getResultList(); 	
> > }
> > 	
> > }
> >
> >
> > How can i get at runtime? To make a query.
> 
> Judging from the code you presented you need at least to return a 
> collection of T (e.g. Iterable<T>) and not a T.
> 
> Cheers
> 
> 	robert
> 
> 
> -- 
> remember.guy do |as, often| as.you_can - without end
> http://blog.rubybestpractices.com/


Robert,

Sure i saw this after i've posted here. So How can I get my current T class in Runtime?

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#30601

Am 19.12.2014 16:13, schrieb Leonan Luppi:
> Em sexta-feira, 19 de dezembro de 2014 12h30min14s UTC-2, Robert Klemme  escreveu:
>> On 19.12.2014 13:23, Leonan Luppi wrote:
>>> Hello,
>>>
>>> I'm try to get generic class type but isn't work. Someone can help
>>> me?  I'm using CDI Weld to Inject my DAO class with a generic type:
>>>
[snip]
>>
>> Judging from the code you presented you need at least to return a
>> collection of T (e.g. Iterable<T>) and not a T.
>>
>> Cheers
>>
>> 	robert
>>
[snip]

Hava a look at https://github.com/jhalterman/typetools
I believe this library will solve your problem.

-- Sebastian

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#30602

Leonan Luppi <leonan.luppi@gmail.com> wrote:
> I'm try to get generic class type but isn't work.

That's not how generics work in Java.

A generic class (like your DAO) just doesn't know what it 
got as its type parameter. To use this type at runtime you
must specify the information explicitly, either as a Class
typed parameter/property, or by use of a factory class (like
AgentFactory) that will implement all type-specific stuff.

A factory instance would then take the place of your "em", or
maybe that of what you obtain from .getCriteriaBuilder(), 
except that it won't need the "HERE_MY_GENERIC_CLASS" argument
to it's methods.

> Someone can help me? I'm using CDI Weld to Inject my DAO class with a generic type:
> @Inject
> private DAO<Agent> dao;
>
> And my DAO Class:
> public class DAO<T> {
> 	
>    public T findAll() {
> 	CriteriaQuery<T> query = em.getCriteriaBuilder()
>                    .createQuery(HERE_MY_GENERIC_CLASS);
> 	query.select(query.from(HERE_MY_GENERIC_CLASS));
> 	return (T) em.createQuery(query).getResultList(); 	
>    }
> }
> How can i get at runtime? To make a query.

return type of findAll has already been discussed in other subthread.

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