Hi Folks, i currently struggle with Kotlin Annotations and the Annotation Processor. I brought up a custom Annotation

Property

@Target(AnnotationTarget.PROPERTY, AnnotationTarget.PROPERTY_GETTER)
@Retention(AnnotationRetention.RUNTIME)
annotation class Property

When using the annotation on a property e.g.:

data class Example(@Property val key: String)

and introspecting the class with a AnnotationProcessor i can find three different elements which are related to that

key

property. The first one is

key

, the second one is

getKey

and the third (which is currently probably the reason for my confusion) is the

getKey$annotations()

one, which is the only element having the annotation from java annotation processor perspective. I would have assumed that either

key

or

getKey

would also be annotated on byte-code level. Any guidance on how i can access the element

getKey

OR

key

using the annotation processor api? My actual goal is to retrieve the name

key

as well as the type

String

of the annotated element

It’s safer to use Kotlin Metadata to inspect Kotlin types as it contains more information. Check out my library https://github.com/fluidsonic/fluid-meta which helps with that, using

Meta.of(yourElement)

. Here I use it in my JSON annotation processor: https://github.com/fluidsonic/fluid-json/blob/accd358687a1247785366625341eeb7ca6be0b99/annotation-processor/sources/jvm-jdk8/collection/CollectionPhase.kt?ts=4#L61

Actually pretty nice library. Thanks @Marc Knaup - gonna give it a try for some other modules I have to write in the next few days But for the fix I rather used a mapping for all

xy$annotations()

to

xy

. Enables me to be compliant with java and kotlin and not just kotlin.

What do you mean by “with Java”? There is no

$annotations

hack in Java 🤔

That’s true actually - but currently i’m using the same AnnotationProcessor for both - java and kotlin. The

$annotations

are only present if it’s processing a kotlin file but still, i can use the entire code for both (as long as i’m sanitizing that

$annotations

thingy when approaching kotlin).

If I recall correctly it’s because Java doesn’t have properties. Kotlin puts field annotation on the JVM field. Kotlin puts getter annotation on the JVM getter. Kotlin puts property annotation on a synthetic JVM getter.

Oh ok. So it’s just synthetic to have a dedicated method to put the property annotations to instead of putting them directly on the field (backed by the getter or similar). Thanks!