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@Resource annotation not injecting a subclass

Answer 1

+1 A:

@Component annotation works only for the class where it's declared, not for its subclasses (for performance reasons, I guess: otherwise it would require traversing of all ancestors for each class being scanned).

As a workaround, you can declare an assignable filter for your parent class in <context:component-scan>:

<context:component-scan base-package = "...">
    <context:include-filter type = "assignable" expression = "... your parent class ..." />
</context:component-scan>

axtavt 2010-03-04 17:53:52

Thanks brother! I assume you mean descendants of the parent class? Also, would this include filter require specifying all classes that might have descendant classes that are not annotated with @Component? This would be awkward and more difficult than adding the annotation! I suppose now is a good time to read about context:include-filter.

stanlick 2010-03-04 21:27:16

@stanlick: I mean that to achieve the desired behaviour Spring should either search all ancestors of each class for `@Component` annotation, or traverse all descendants of `@Component`-annotated class. Startup speed would suffer in both cases. And yes, I meant a separate filter declarations for each parent class, because I can't see any other ways, except for `@Component` at each child class.

axtavt 2010-03-04 21:46:45

Great explanation! Yeah, adding (the redundant) @Component results in appropriate injections in child classes but seems to be a little silly. To me it's like "double" configuration. If Foo extends Bar and Bar is injected, Foo should be too as a result of Foo BEING-A Bar.

stanlick 2010-03-05 14:06:06

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