Hi, I got next case with spring boot rest api:

@RestController
@RequestMapping("/my_controller")
class MyController {

    @GetMapping(produces = [MediaType.APPLICATION_JSON_VALUE])
    fun getIds(@RequestParam(value = "ids") ids: List<Long>): List<Long> = ids
}

when I call for example:

curl -ik localhost:8080/my_controller?ids=1,2,3

all good but when my client send an empty value for example:

curl -ik localhost:8080/my_controller?ids=1,,3

the list

ids

don't check nullability and my method got

[1,null,3]

I suppose the problem around conversion from java to kotlin cause when I decompile class to java I see next

@NotNull
public List getIds(@RequestParam("ids") @NotNull List ids) {
   Intrinsics.checkNotNullParameter(ids, "ids");

there is no any nullability checking, any ideas how to fix it, and where is the root of problem? thanks.

tbf, your

ids

value is indeed not null 😛 you can use this on it though: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/filter-not-null.html

Hi. Might be wrong but looks like it's on Spring Boot side: https://docs.spring.io/spring-boot/docs/2.0.x/reference/html/boot-features-kotlin.html#boot-features-kotlin-null-safety https://github.com/spring-projects/spring-framework/issues/20496

You could also change the parameter to String and do parsing/validation yourself - if this floats your boat.

@Alexander Levin looks like, thanks.