java annotation on scala method parameter

Question

I'm learning scala. I want to put a java annotation (let's say lombok's @NotNull) on scala method parameter. but when I write:

def a(@NotNull o : Object) = {}

I get a compilation error: trait NotNull is abstract; cannot be instantiated.

ps. I'm not asking how to ensure not null in scala. I'm asking how to use java annotation

Community · Accepted Answer · 2017-05-23 10:33:27Z

2

That's the correct way to use a Java annotation in scala

scala> import java.lang.annotation._
...
scala> def a(@Retention(RetentionPolicy.RUNTIME) o: Object) = {}
a: (a: Object)Unit

By the way NotNull is scala specific which is the cause of the error. Martin Odersky explains this issue

edited May 23, 2017 at 10:33

CommunityBot

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answered Mar 14, 2014 at 17:50

loki

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Comments

Ed Staub · Accepted Answer · 2014-03-14 18:22:24Z

1

There's no Lombok @NotNull; there's a Scala @NotNull and a Lombok @NonNull.

Scala's @NotNull has never been correctly implemented, and has been deprecated (with implementation removed) in 2.11. See https://issues.scala-lang.org/browse/SI-7247 . So if that was the subject, the question is probably moot.

I'd be surprised if Lombok @NonNull works in Scala source. Lombok uses a (Java) compile-time annotation processor. Since Scala compiles direct to bytecode, Java annotation processors are not invoked.

Since neither of these are of use, you might want to ask around for alternatives.

edited Mar 14, 2014 at 18:22

answered Mar 14, 2014 at 18:05

Ed Staub

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1 Comment

piotrek Over a year ago

you're right. my ide mixed up annotations. after fix i have no more compiler errors. still haven't check if lombok works with scala

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