[cdi-dev] Bean<T> that only qualifies super types?

arjan tijms arjan.tijms at gmail.com
Fri Aug 7 05:43:09 EDT 2015


On Fri, Aug 7, 2015 at 11:27 AM, Martin Kouba <mkouba at redhat.com> wrote:
> I believe the bean class should not be abstract. It's not clearly defined
> but there are some indirect suggestions: abstract class is not a managed
> bean -> Bean.getBeanClass() returns the bean class of the managed bean...
> etc.

Hmmm, but it can be an interface right? And the difference between an
interface and a "pure" abstract class (abstract class with only
abstract methods) is rather minimal.

The instance that is returned is not abstract (of course), but both a
producer and a Bean<T> can have interfaces as their "declared"  bean
Type if I understood correctly.


public Interface produce() {
   return new InterfaceImpl();

There's nothing wrong with that, is it?

So by extension, is this wrong then?

public Foo produce() {
   return new FooImpl();

> No, this is not possible. Qualifiers are tied to a bean definition, not to a
> bean type.

So this would possibly be an enhancement or new feature request then.

I did found a workaround though, which seems to work because the Type
I'd like to hide happens to have generic parameters:

private static class Dummy {}

public Set<Type> getTypes() {
    return new HashSet<Type>(asList(Foo.class,
ParameterizedTypeImpl(Map.class, new Type[]{Dummy.class,

With those types the proxy that's generated contains methods for both
Foo and Map, but because the generic parameters are the private class,
the client application can never declare an injection point for this
(certain not accidentally).

Another possible workaround I thought of is using a second Bean<T>
that only has Foo as its type and is @Dependent scoped, which then
asks the bean manager for an instance of a qualified Foo (qualifier is
of a private type). If I'm not mistaken the first Bean<T> would then
be called and an @RequestScoped proxy would be returned, which the
second Bean<T> can then return from its create() method.

What do you think, any of these methods have potential unforeseen
side-effects or are they safe to use?

Kind regards,

>> Kind regards,
>> Arjan Tijms
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> --
> Martin Kouba
> Software Engineer
> Red Hat, Czech Republic

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