Kotlin 扩展 spring 引导注释

Question

With Kotlin I'm able to save defaults in a class level annotation, eg

@Profile("dev", "staging", "production")
annotation class RemoteProfile

I'm curious if there's a way of achieving something similar with parameter annotations - for example I'd love to be able to do something like:

fun someHandler(@AccountParam account: Account) {
   ...
}

Where underneath spring would interpret it as

fun someHandler(@RequestAttribute("ACCOUNT") account: Account) {
   ...
}

Answer 1

The concept you're looking for is meta-annotation . The reason your first example works has nothing to do with Kotlin and is a feature of Spring, where Spring actively inspects the annotation hierarchy. From the Javadoc for Profile :

The @Profile annotation may be used in any of the following ways:

• …
• as a meta-annotation, for the purpose of composing custom stereotype annotations

The MVC annotations RequestAttribute and RequestParam don't support meta-annotation. You could define your own HandlerMethodArgumentResolver s to support this (it's not terribly complicated, and you could subclass RequestAttributeMethodArgumentResolver ), but you can't just meta-annotate in general.

(Groovy's AnnotationCollector does support this, but it's implemented by a compile-time "unrolling", and I don't believe Kotlin has an equivalent feature.)