That is interesting problem. Here is a simplified version of it:
class General<A>{
General(Class<A> klass){
}
}
class Specific extends General<List<String>>{
Specific() {
super(List.class);
}
}
The super line will have an error. It seems to me that using class
literals breaks down when using nested generics like that.
You might want to try posting that to a java dev list and see what
people say. I'd guess you'd get responses saying wait
for java 7 where it sounds like generics are more available at runtime.
To work around it I can see 2 options:
1. you could loose some type safety and remove the nesting like this:
public class ELODaoImpl extends AbstractJcrDAO<CmsELOImpl> {
private static final String[] MIXIN_TYPES = { "mix:versionable" };
public ELODaoImpl( Session session, Jcrom jcrom ) {
super(CmsELOImpl.class ,session , jcrom, MIXIN_TYPES);
}
2. you could pass in the class to the method. This might just push the
problem up, but perhaps you have
and instance of CmsELOImpl< IMetadataKey> when you call the constructor.
public class ELODaoImpl extends AbstractJcrDAO<CmsELOImpl< IMetadataKey>> {
private static final String[] MIXIN_TYPES = { "mix:versionable" };
public ELODaoImpl(Class<CmsELOImpl< IMetadataKey>> klass, Session
session, Jcrom jcrom ) {
super(klass ,session , jcrom, MIXIN_TYPES);
}
Scott
Rokham Sadeghnezhadfard wrote:
> Thank you all for your replies.
>
> Here's a snippet of the code:
>
> *This is my class and my constructor. If you notice the first line of
> the constructor calls the super method.*
>
> public class ELODaoImpl extends AbstractJcrDAO<CmsELOImpl<
> IMetadataKey>> {
>
> private static final String[] MIXIN_TYPES = { "mix:versionable" };
>
> public ELODaoImpl( Session session, Jcrom jcrom ) {
> super(<CmsELOImpl<IMetadataKey>> ,session , jcrom, MIXIN_TYPES);
> }
>
> My problem is that on the first parameter of super I have to send the
> Class object for CmsELOImpl<IMetadada> and I don't know how.
>
> Here's the signature of AbstractJcrDAO's constructor
>
>
> public abstract class AbstractJcrDAO<T> implements JcrDAO<T> {
>
> /**
> * Constructor.
> *
> * @param entityClass the class handled by this DAO implementation
> * @param session the current JCR session
> * @param jcrom the Jcrom instance to use for object mapping
> * @param mixinTypes an array of mixin types to apply to new nodes
> */
> public AbstractJcrDAO( Class<T> entityClass, Session session,
> Jcrom jcrom, String[] mixinTypes ) {
>
> Thank you in advance,
>
> Rokham
>
>
>
> On Wed, Oct 8, 2008 at 12:11 PM, Scott Cytacki <[EMAIL PROTECTED]
> <mailto:[EMAIL PROTECTED]>> wrote:
>
>
> Stephen Bannasch wrote:
> >> Hi all,
> >>
> >> I'm having a hard time loading the '.class' object of a java
> generic class. In the older java if I had a class Student, I could
> simply call Student.class and get its Class object. But now if I
> have a Class <A <B>>, I've tried all the possible ways I could
> think of to get it's class object but I wasn't able. I've tried
> the net as well but I was out of luck :(.... My work is kind of
> halted unless I solve this little problem so if anyone has more
> experience with Java Generics, your help is much appreciated.
> >>
> >
> > Can you show the simplest code which demonstrates the problem?
> >
>
> My guess is that you want to get the class object from a type
> parameter.
> That is something I wanted to do too, but that is actually not
> possible.
> The fundamental reason is that the type information for generics
> is not
> available at runtime.
>
> For example the following isn't possible:
>
> <T> void addNew(List<T> list) throws Exception{
> list.add(T.class.newInstance());
>
> }
>
>
> If you need to get the class from a type parameter, the best you
> can do
> is pass it in. So the
> method above would look like this:
>
> <T> void addNew(List<T> list, Class<T> klass) throws Exception{
> list.add(klass.newInstance());
> }
>
> Scott
>
>
>
>
>
> --
> Rokham
>
> >
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