MergedAnnotations search does not find container for repeatable annotation

[heihei180]

when i use applicationContext.getBeansWithAnnotation(Extensions.class);
in spring framework 5.3.20 , i can got a bean,
in spring framework 5.3.28, i can't got a bean.

---

definition of Extensions:

@Inherited
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE})
@Component
public @interface Extensions {

    String[] bizId() default BizScenario.DEFAULT_BIZ_ID;

    String[] useCase() default BizScenario.DEFAULT_USE_CASE;

    String[] scenario() default BizScenario.DEFAULT_SCENARIO;

    Extension[] value() default {};

}

Definition of variable "applicationContext":

@Component
public class ExtensionBootstrap implements ApplicationContextAware {
    private ApplicationContext applicationContext;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.applicationContext = applicationContext;
    }
}

Can someone tell me what changes have occurred here?
I think this should be a problem, but I couldn't find where the problem occurred.

[snicoll]

@heihei180 I am not sure what could have changed this. The code in text you've shared isn't actionable unfortunately, please share a small sample we can run ourselves that reproduces this behavior. You can attach a zip here or push the code to a GitHub repository.

[heihei180]

@snicoll Thank you for your reply~

I will upload a zip file that contains two folders, demo1 and demo2, both of which are springboot programs, but the versions are different.

• the spring boot version for demo1 is 2.6.8, the spring framework version used is 5.3.20,
• the spring boot version for demo2 is 2.7.13, and the spring framework version used is 5.3.28
  Additionally, you can run unit tests for two projects, and demo1 (5.3.20) will run successfully,
  Demo2 (5.3.28) will fail to run!
  testSpring.zip

Looking forward to your reply! Thank you again.

[snicoll]

Thanks for the sample. I can reproduce, including with the latest release and I don't know if that's intended.

Relying on the container annotation for this looks a bit odd to me though. If you use Extension it works obviously and I would expect you to use that, rather than the @Repeatable container. I've asked @sbrannen if that rings a bell.

[sbrannen]

Thanks for the demo projects, @heihei180. 👍

I've reduced this to the following test.

@Test
void test() {
	Extensions extensions = FooService.class.getAnnotation(Extensions.class);
	assertThat(extensions).as("@Extensions").isNotNull();

	extensions = MergedAnnotations.from(FooService.class, SearchStrategy.TYPE_HIERARCHY)
			.get(Extensions.class)
			.synthesize(MergedAnnotation::isPresent)
			.orElse(null);
	assertThat(extensions).as("@Extensions").isNotNull();
}

java.lang.Class.getAnnotation(Class<Extensions>) of course finds @Extensions on FooService, but Spring's MergedAnnotations support no longer does.

I consider that a regression, and I'll investigate further.

[sbrannen]

The above test actually fails on 5.3.20 as well if you remove all attributes from Extensions.class except the value attribute.

This appears to be related to #29685, and I assume this bug may have existed since Spring Framework 5.2 when the MergedAnnotations infrastructure was introduced.

[sbrannen]

This issue turned out be an interesting one... and a combination of a few things.

The above test actually fails on 5.3.20 as well if you remove all attributes from Extensions.class except the value attribute.

That's due to a bug in the MergedAnnotations support that has existed since it was introduced in 5.2.

Specifically, if the MergedAnnotations API is used to search for annotations with "standard repeatable annotation" support enabled (which is the default), it's possible to search for the repeated annotations but not for the container itself.

The reason is that MergedAnnotationFinder.process(Object, int, Object, Annotation) does not process the container annotation and instead only processes the "contained" annotations.

This appears to be related to #29685, and I assume this bug may have existed since Spring Framework 5.2 when the MergedAnnotations infrastructure was introduced.

That's indeed the case: #29685 allowed the MergedAnnotations infrastructure to recognize an annotation as a container even when the annotation declares attributes other than value.

In other words, since Spring Framework 5.3.25, MergedAnnotations considers the @Extensions annotation a container, and due to the aforementioned bug the container is no longer processed, which results in a regression in behavior for use cases like the one in the supplied demo projects.

[sbrannen]

This has been addressed in 4baad16 which will be included in Spring Framework 6.1.7, 6.0.20, and 5.3.35.