在Scala中注释构造函数参数

Question

Annotating constructor parameters seems to do nothing when compiled to bytecode. I get no compiler warnings either.

The following works. getAnnotations for the name field returns javax.annotation.Nullable .

class Person {
    @Nullable var name: String = _;
}

The following doesn't, neither with val or var .

class Person(@Nullable var name: String)

This is probably not intentional, so is there something I am missing or should I go file a bug report?

Answer 1

You need to specify what should get annotated when you specify annotations on constructor parameters.

To do that annotate your annotation with one ore more annotations from scala.annotation.target , eg getter , setter or as in your case field :

import annotation.target.field

class Person(@(Nullable @field) var name: String)

You can also use type aliases for that:

type NullableField = Nullable @field

class Person(@NullableField var name: String)

Update Scala 2.12

Now this specific annotation and others are in the package scala.annotation.meta rather than scala.annotation.target

import scala.annotation.meta.{field, param}