Pseudo-meta-annotation for @ImportAutoConfiguration

[dsyer]

It would be nice to be able to @ImportAutoConfiguration(Foo.class) where Foo is itself annotated with @ImportAutoConfiguration(Bar.class) and for Bar to end up in the list of autoconfigs to be sorted and applied. It's almost a meta-annotation, but actually requires (I think) some conscious link following.

[philwebb]

That might have some interesting knock on effects with regular auto-configuration since presumably only Foo would be in the spring.factories file but both Foo and Bar would end up being considered.

What's driving the desire for such a change?

[dsyer]

I don't know about the knock on effects exactly. The @ImportAutoConfiguration annotation isn't used in the spring.factories route AFAIK, but I don't see why this idea shouldn't apply to both with no conflicts. At the end of the day you get a list of unique autoconfig class names (from somewhere) and sort them. I think a meta feature like this could be applied to that list before it is consumed/sorted independent of the source of the initial list.

The driver is experimenting with grouping autoconfig classes together in curated sets, implemented simply as classes annotated with @ImportAutoConfiguration. Previous implementations of this have relied on custom annotations that followed the meta links. But @ImportAutoConfiguration seems to say what it means to do already, and not actually deliver what I needed.

[dsyer]

Actually, on reflection, I got this wrong. I can always use @Import(Foo.class) and that will work. The problem might be simpler. This works:

@ImportAutoConfiguration(Bar.class)
@SpringBootConfiguration(proxyBeanMethods = false)
@ComponentScan
@AutoConfigurationPackage
@Import(Foo.class)
public class MyApplication { ... }

but this doesn't

@ImportAutoConfiguration(Bar.class)
@MySpringBootApplication(Foo.class)
public class MyApplication { ... }

with

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@SpringBootConfiguration(proxyBeanMethods = false)
@ComponentScan
@Import({})
@AutoConfigurationPackage
public @interface MySpringBootApplication {

	@AliasFor(annotation = Import.class)
	Class<?>[] value() default {};

}

If I can understand that, it might need a tweak in Boot, or it might be something I can fix in my code.

[philwebb]

It looks to me like Spring Framework doesn't currently support @Import as a meta-annotation. I think this code would need to change.

[philwebb]

@dsyer Are you still interested in this one?

[dsyer]

Still interested yes. Not actively working on anything that needs it though, so not urgent. I would probably do more work if this feature became available somehow.