CDI. Using @Specializes

Question

I have a question about using @Specialization. As prescribed by the Java EE 6 or 7 tutorials if I declare my bean by giving it @Specializes annotation that it ' ll completely replace bean, which extends my bean. E.g.

    public interface I {}
    @Default @Q
    public class A implements I {}
    @Specializes
    public class SpecA extends A {}
    ////
    a) @Inject I a;
    b) @Inject @Q I b;

Is it enough for that SpecA will be injected to fields 'a' and 'b'? I tried to run this example on glassfish 4.0 and it didn't worked.

I have read strange sentences in tutorials: 'Usually, a bean marked with the @Specializes annotation is also an alternative and is declared as an alternative in the beans.xml file. ' I don't understand what should I do to do make it work as prescribed in tutorials? Do I need add annotation @Alternative and add this class to beans.xml? Or Do I need add my bean to beans.xml?

Answer 1

To answer your questions

Do I need add annotation @Alternative and add this class to beans.xml?

Yes

Do I need add my bean to beans.xml?

No. Above will do

Giving you more context :

@Specializes is more or less meant to specialize an @Alternative bean.

@Specializes comes handy when the @Alternative bean is meant to replace

• a bean/implementation that is annotated with one or more qualifiers and
• the injection points are using the one/more qualifiers.

Case 1 : You have one bean/implementation (lets call BeanA) with no qualifiers. In this case you don't need @Specializes, you will have to

1. Create a @Alternative bean (let's call AltBean) that you want to use as a replacement for BeanA
2. List AltBean in beans.xml as alternative

Case 2 : You have one bean/implementation (in your case A) with one or more qualifiers. In this case you have to

1. Create a @Alternative and @Specializes bean (SpecA) that you want to use as a replacement for A
2. Make SpecA extend A
3. List SpecA in beans.xml as alternative

Yours is Case 2.