Java 16 Annotation ElementType.RECORD_COMPONENT cannot be reflected

Question

Using JDK 16, I declared two annotations:

@Target({ ElementType.RECORD_COMPONENT})
@Retention(RetentionPolicy.RUNTIME)
public @interface A {}

@Target({ ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
public @interface B {}

And I declared a record class like this：

public record User(@A @B long id, String name, int age) {}

Then I use reflection to fetch the annotations of id, which is:

Annotation[] annotations = fields[0].getAnnotations();

But the size of annotations is one and I only got @B, why is that? Thanks

Answer 1

Annotations on record components are propagated to potentially four places in the classfile:

• fields
• accessor methods
• constructor arguments
• record components themselves.

These are gated by whether the annotation is applicable to

• FIELD
• METHOD
• PARAMETER
• RECORD_COMPONENT

it will be propagated to all the places it is applicable. If it is not applicable to any of these, it is rejected at compile time.