Re: [seam-dev] CDI with generic class and the hell of type erasure.

Nice solution Ales, wish I'd thought of it :) On Tue, Dec 6, 2011 at 15:45, Ales Justin <ales.justin(a)gmail.com&gt; wrote: > You could do something like this: > > @SuppressWarnings({"unchecked"}) > @Produces > public GenericQuery injectClass(InjectionPoint ip) { > Annotated annotated = ip.getAnnotated(); > Class clazz = Object.class; > Type type = annotated.getBaseType(); > if (type instanceof ParameterizedType) { > ParameterizedType pt = (ParameterizedType) type; > clazz = (Class) pt.getActualTypeArguments()[0]; > } > return new GenericQuery(clazz); > } > > -- > > @Inject > GenericQuery<String> gqs; > @Inject > GenericQuery<Number> gqn; > > -- > > System.out.println("GQS: " + gqs.getClazz()); > System.out.println("GQN: " + gqn.getClazz()); > > -- > > GQS: class java.lang.String > GQN: class java.lang.Number > > -- > > > https://github.com/alesj/cdi-arq-workshop/commit/64860f15197be40a7714dfd8... > > HTH > > -Ales > > Hey guys, how you doing? > > I'm trying to achieve something that might be impossible, but before > concluding that, I'd like to ask you, CDI gurus! > > I have the following class: > > public class Foo<T> { > > public TypedQuery<T> getQuery(){ > > } > > } > > As you can Imagine, inside my getQuery method, I'd have to use "T.class" > to make it TypedQuery. which is impossible due java generics type erasure. > > so I'd have to build a private field to hold the t.class for me. > > public class Foo<T> { > > private Class<T> klass; > > public TypedQuery<T> getQuery(){ > > } > > public void setKlass(Class<T> klass){ > this.klass = klass; > } > } > > The problem is that forcing this 'setKlass' feels very ugly to the api, > and it's not very error prone, since one could easily forget to set this > configuration. > > So I had an Idea: force the setKlass inside the constructor: > > public class Foo<T> { > > private Class<T> klass; > > public Foo(Class<T> klass){ > this.klass = klass; > } > > public TypedQuery<T> getQuery(){ > > } > > } > > Unfortunatelly, this breaks cdi, since it cannot inject it anymore. At > least AFAIK. > > So, is there a way out of this? maybe using a secret solder feature? > _______________________________________________ > seam-dev mailing list > seam-dev(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/seam-dev > > > > _______________________________________________ > seam-dev mailing list > seam-dev(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/seam-dev > > -- Jason Porter http://lightguard-jp.blogspot.com http://twitter.com/lightguardjp Software Engineer Open Source Advocate Author of Seam Catch - Next Generation Java Exception Handling PGP key id: 926CCFF5 PGP key available at: keyserver.net, pgp.mit.edu