AnnotationMetadata.getAnnotationAttributes inconsistency for empty array in ASM implementation [SPR-17347]

[spring-projects-issues]

LutherWest opened SPR-17347 and commented

Different implementations of AnnotationMetadata provides different annotation attributes. Currently, it makes ImportBeanDefinitionRegistrar inconsistent due to provided AnnotationMetadata in registerBeanDefinitions(...) method.

 

For the test case below, StandardAnnotationMetadata will return an empty String array (as expected). But AnnotationMetadataReadingVisitor will return Hello world!.

 

Please, consider the following test case:

@SpringBootTest(classes = ClassAnnotationMetadataTest.class)
@ClassAnnotationMetadataTest.SimpleAnnotation(arrayProperty = {}) // force emptiness
@RunWith(SpringRunner.class)
public class ClassAnnotationMetadataTest {

    @Autowired
    private ResourceLoader resourceLoader;

    private MetadataReaderFactory metadataReaderFactory;

    @Before
    public void setup() {
        this.metadataReaderFactory = new CachingMetadataReaderFactory(resourceLoader);
    }

    @Test
    public void annotationMetadataResultInconsistency() throws IOException {
        AnnotationMetadata meta1 = new StandardAnnotationMetadata(ClassAnnotationMetadataTest.class);
        AnnotationMetadata meta2 = metadataReaderFactory.getMetadataReader(ClassAnnotationMetadataTest.class.getName())
                .getAnnotationMetadata();

        Assertions.assertThat(meta1)
                .isInstanceOf(StandardAnnotationMetadata.class)
                .extracting(meta -> meta.getAnnotationAttributes(SimpleAnnotation.class.getName()))
                .containsAnyOf(entry("arrayProperty", new String[]{ }));
        Assertions.assertThat(meta2)
                .isInstanceOf(AnnotationMetadataReadingVisitor.class)
                .extracting(meta -> meta.getAnnotationAttributes(SimpleAnnotation.class.getName()))
                .containsAnyOf(entry("arrayProperty", new String[]{ }));
    }

    @Retention(RetentionPolicy.RUNTIME)
    @Target(ElementType.TYPE)
    public @interface SimpleAnnotation {
        String[] arrayProperty() default "Hello world!";
    }
}

 

A bit more details, which I can found:

https://github.com/spring-projects/spring-framework/blob/master/spring-core/src/main/java/org/springframework/core/type/classreading/RecursiveAnnotationAttributesVisitor.java#L46

This line will trigger registration of default values for annotation.

For given test case, explicitly specified empty array will be treated as absence of value (associated AnnotationAttributes object won't contain 'arrayProperty' value) and default one will be picked up.

 

Finally

Is it expected behavior?

---

Affects: 5.0.7

Issue Links:

• AnnotationMetadataReadingVisitor.getMetaAnnotationTypes(String) may return null but it is not marked @Nullable [SPR-17046] #21584 AnnotationMetadataReadingVisitor.getMetaAnnotationTypes(String) may return null but it is not marked @Nullable

Referenced from: commits 5343076, 83909e6

Backported to: 5.0.10

[spring-projects-issues]

Juergen Hoeller commented

We consistently expose empty arrays even with ASM parsing now, checking the absence of a visitor callback for an attribute of array type and explicitly exposing an empty array in that case.