Can't component scan for @Component and exclude @Controller (a.k.a., excludeFilters should take precedence over includeFilters) [SPR-9795]

[spring-projects-issues]

Nick Williams opened SPR-9795 and commented

Like many, I wanted my services, repositories and the like managed by the application context and my controllers by the framework servlet. So, for my application context configuration class I used the following annotation:

@ComponentScan(basePackageClasses={
        com.package.Marker.class
}, useDefaultFilters=true, includeFilters={
        @ComponentScan.Filter(Aspect.class)
}, excludeFilters={
        @ComponentScan.Filter(Controller.class)
})

And for my framework servlet configuration I used:

@ComponentScan(basePackageClasses={
        com.package.Marker.class
}, useDefaultFilters=false, includeFilters={
        @ComponentScan.Filter(Controller.class)
})

However, my controllers were getting instantiated twice: once in the application context and once in the framework servlet. So I tried the following iterations of my application context config class annotation:

@ComponentScan(basePackageClasses={
        com.package.Marker.class
}, useDefaultFilters=false, includeFilters={
        @ComponentScan.Filter(Aspect.class), @ComponentScan.Filter(Component.class),
        @ComponentScan.Filter(Repository.class), @ComponentScan.Filter(Service.class)
})

@ComponentScan(basePackageClasses={
        com.package.Marker.class
}, useDefaultFilters=false, includeFilters={
        @ComponentScan.Filter(Aspect.class), @ComponentScan.Filter(Component.class),
        @ComponentScan.Filter(Repository.class), @ComponentScan.Filter(Service.class)
}, excludeFilters={
        @ComponentScan.Filter(Controller.class)
})

Neither of those worked. Controllers were instantiated twice. I figured this is because the @Controller annotation is itself annotated with @Component. So, with that, THIS worked:

@ComponentScan(basePackageClasses={
        com.package.Marker.class
}, useDefaultFilters=false, includeFilters={
        @ComponentScan.Filter(Aspect.class), @ComponentScan.Filter(Repository.class),
        @ComponentScan.Filter(Service.class)
})

However, that doesn't achieve what I want, because I want classes marked @Component to be instantiated, I just don't want classes marked @Controller to be instantiated.

In short, it seems to me that if I explicitly say "exclude classes matching these filters from component scanning," that should take precedence over all else. Especially important: if I say "use default filters" and then provide exclusions, those exclusions should NOT be ignored.

I do not know whether this same problem exists with XML configuration. Presumable it does, but I'm not in a position to test that at the moment.

---

Affects: 3.1.2

0 votes, 5 watchers

[spring-projects-issues]

Chris Beams commented

Thanks Nick, will take a look at this. In the meantime, feel free to submit a simple reproduction project.

[spring-projects-issues]

Nick Williams commented

By the way, since I reported this I have confirmed that this problem does not exist in the XML equivalent of the configuration above (forgive any misspellings, these were transcribed, not copied and pasted):

<context:component-scan base-package="com.package" use-default-filters="true">
    <context:include-filter type="annotation" expression="org.aspectj.lang.annotation.Aspect" />
    <context:exclude-filter type="annotation" expression="org.springframework.stereotype.Controller" />
</context>

<context:component-scan base-package="com.package" use-default-filters="false">
    <context:include-filter type="annotation" expression="org.springframework.stereotype.Controller" />
</context>

So, the above works just as expected. The application context instantiates @Services, @Repositories, @Components and @Aspects, but it does NOT instantiate @Controllers. Then the servlet context instantiates @Controllers. This is the correct behavior (from my perspective, i.e., this was the INTENDED behavior). However, it differs from the @Configuration behavior. IMO, these behaviors should be identical.

This should work the same as my applicationContext.xml above (it does not):

@ComponentScan(basePackageClasses={
        com.package.Marker.class
}, useDefaultFilters=true, includeFilters={
        @ComponentScan.Filter(Aspect.class)
}, excludeFilters={
        @ComponentScan.Filter(Controller.class)
})

And this should work the same as my servletContext.xml above (it does):

@ComponentScan(basePackageClasses={
        com.package.Marker.class
}, useDefaultFilters=false, includeFilters={
        @ComponentScan.Filter(Controller.class)
})

[spring-projects-issues]

Phil Webb commented

Hi Nick,

After a bit of digging I think this might not actually be a bug. From your notes it looks like your two @Configuration classes are both contained in the same package. What I think is happening is that your top configuration (the one the filters @Controllers) is scanning your base package for all @Components. Because @Configuration classes are meta-annotated with @Component the scanning actually finds and processes your second configuration, bringing in the @Controller classes.

Try adding an additional exclude filter to prevent the second configuration class from being found. If you don't want any @Configuration classes to be scanned you can use the following:

Application:

@ComponentScan(
  basePackageClasses={com.package.Marker.class}, 
  useDefaultFilters=true, 
  includeFilters={@Filter(Aspect.class)},
  excludeFilters={@Filter(Controller.class, Configuration.class)})

Servlet:

@ComponentScan(
  basePackageClasses={com.package.Marker.class},
  useDefaultFilters=false, 
  includeFilters={@Filter(Controller.class)
})

I have created a repro project to show the fix:
spring-attic/spring-framework-issues@a1519b6

Cheers,
Phil.

[spring-projects-issues]

Nick Williams commented

Phil, this is not correct. Here is my actual project structure for the concerned classes:

-> com
    -> companyname
        -> config
            -> ApplicationContext.java
            -> ServletContext.java
        -> product
            -> health
                -> Marker.java

The actual basePackageClasses value is com.companyname.product.health.Marker.class. This is not in the same package as the config classes. Therefore, this is not the cause of the issue.

[spring-projects-issues]

Nick Williams commented

(Sorry that the comment was improperly formatted before. I have resolved this.)

[spring-projects-issues]

Phil Webb commented

Hi Nick,

Thanks for the update, I thought I was onto the root cause there!

I am having some trouble replicating the issue, could you take a look at #14428 in https://github.com/SpringSource/spring-framework-issues to see if you can see any obvious differences between that project and your code.

Cheers,
Phil.

[spring-projects-issues]

Nick Williams commented

OMG ... I'm so sorry I wasted your time, Phil (and my time). I just spent the last two hours slowly building a reproduction project and bit by bit I couldn't get it to reproduce, up until the point that I had replicated the entire project and still couldn't get it to reproduce. I couldn't figure out what the @$#! was going on, and then I realized...

The Marker.java was in the wrong package.

...

I can't tell you how many months I have looked at that folder structure and never realized it was in the wrong package. I KNEW it was supposed to be in .product, I KNEW putting it above .product (and, thus, above .config) could cause problems, and I KNEW that I had put it in .product. But I hadn't. Either that or somebody else on the team moved it. Either way, it was above .product and .config, thus causing so many problems that I hadn't even realized.

sigh

Sorry

[spring-projects-issues]

Phil Webb commented

No worries. We've all been there!