CDI method injection and bean inheritance in Java

Question

What I want to do - I have a child and parent class. Child has SimpleFoo, Parent needs Advaced foo. So,

@Dependent
public class SimpleFoo {
}

@Dependent
public class AdvancedFoo extends SimpleFoo {
}

@Dependent
public class Child {

    private SimpleFoo foo;

    @Inject
    protected void setFoo(SimpleFoo foo) {
        this.foo = foo;
    }
}

@Dependent
public class Parent extends Child {

    @Inject
    @Override
    protected void setFoo(SimpleFoo foo) { //How to inject here AdvancedFoo
        super.setFoo(foo);
    }
}

I know that I can do it via constructor injection but I need method injection. How to do it? Can it be done without using names (like MyBean1) but only using classes (AdvancedFoo)?

Answer 1

Use qualifiers - you now have two beans which both fulfill your requirements on type; you need to limit that and qualifiers are made for such cases.

Here is how to do it, first the qualifier:

@Qualifier
@Retention(RetentionPolicy.RUNTIME)
@Target({ ElementType.TYPE, ElementType.PARAMETER, ElementType.FIELD, ElementType.METHOD })
public @interface MyQualifier {
}

Now, make your AdvancedFoo bean use that qualifier:

@Dependent
@MyQualifier
public class AdvancedFoo extends SimpleFoo {
...
}

And finally, in the init method, inject a bean of type SimpleFoo and with qualifier @MyQualifier:

@MyQualifier
public class Parent extends Child {

    @Inject
    protected void setFoo(@MyQualifier SimpleFoo foo) {
        this.foo = foo;
    }
}