How to fix warning in Kotlin: Assigning single elements to varargs in named form is deprecated

Question

After upgrading Kotlin from 1.1.4 to latest 1.2.22, I got a lot of build warnings:

[WARNING] ... (422, 29) Assigning single elements to varargs in named form is deprecated

The related code is like this:

422     @RequestMapping(value = "/privacy", method = arrayOf(RequestMethod.GET))
423     fun mainLinkPrivacy(request: HttpServletRequest, model: MutableMap<String, Any>): String {
424 
425         var lang = request.getParameter("lang")
426 
427         if(lang == null || lang.isEmpty())
428             lang = "EN"
429 
430         model.put("lang",lang)
431 
432         return "/mobile/main/mainlink_privacy"
433     }

And here is the import part:

import org.apache.ibatis.annotations.Param
import org.springframework.beans.factory.annotation.Autowired
import org.springframework.core.env.Environment
import org.springframework.stereotype.Controller
import org.springframework.web.bind.annotation.RequestMapping
import org.springframework.web.bind.annotation.RequestMethod
import org.springframework.web.bind.annotation.RequestParam

import javax.servlet.http.HttpServletRequest

And here is my Kotlin version:

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <java.version>1.8</java.version>
    <kotlin.version>1.2.21</kotlin.version>
    <dokka.version>0.9.15</dokka.version>
    <spring.framework.version>4.3.1.RELEASE</spring.framework.version>
</properties>

I think the problem exist in method = arrayOf(), but how to fix this?

I read the Kotlin release note about this Deprecation: single named argument for vararg, it says:

---

"For consistency with array literals in annotations, passing a single item for a vararg parameter in the named form (foo(items = i)) has been deprecated. Please use the spread operator with the corresponding array factory functions:

foo(items = *intArrayOf(1))

There is an optimization that removes redundant arrays creation in such cases, which prevents performance degradation. The single-argument form produces warnings in Kotlin 1.2 and is to be dropped in Kotlin 1.3."

---

But I still don't find hints about how to fix it.

Answer 1

I think that not deprecated form is value = ["/privacy"], method = [RequestMethod.GET].

More documentation on how to use annotations in kotlin can be found here