Kotlin: problems with data classes #2281
Description
- Is this an issue (and hence not a question)?
I'm trying to use MapStruct with kotlin codebase. For the most part i'm pretty successfull, but i have 2 issues that are weird and require workarounds that shouldn't be necessary.
First issue that i have is that if i try to map data class with single field i have to explicitly ignore "copy" target in mapper annotation because i'm getting warning "Unmapped target property: "copy"". When i add second field - it's no longer needed. Example:
data class SinglePropertyTest(val property: String)
data class SinglePropertyTestDto(val property: String)
data class DoublePropertyTest(val property1: String, val property2: Int)
data class DoublePropertyTestDto(val property1: String, val property2: Int)
@Mapper
interface SinglePropertyMapper {
// this gives me warning - Unmapped target property: "copy"
fun toDto(singlePropertyTest: SinglePropertyTest): SinglePropertyTestDto
// this works just fine
fun toDto(doublePropertyTest: DoublePropertyTest): DoublePropertyTestDto
}Seconds issue is more dangerous. If class have all fields nullable with default value set to null - mapper is silently failing to map any properties (all properties in target class are null). Example:
fun main(args: Array<String>) {
val allNullClass = AllNullClass("test", null)
val mapper = Mappers.getMapper(AllNullMapper::class.java)
val mappedDto = mapper.toDto(allNullClass)
// property1 here is null !
assert(mappedDto.property1 != null)
assert(mappedDto.property2 == null)
}
data class AllNullClass(
val property1: String? = null,
val property2: Int? = null
)
data class AllNullClassDto(
val property1: String? = null,
val property2: Int? = null
)
@Mapper
interface AllNullMapper {
fun toDto(allNullClass: AllNullClass): AllNullClassDto
}Generated code looks like that:
public class AllNullMapperImpl implements AllNullMapper {
@Override
public AllNullClassDto toDto(AllNullClass allNullClass) {
if ( allNullClass == null ) {
return null;
}
AllNullClassDto allNullClassDto = new AllNullClassDto();
return allNullClassDto;
}
}It seems like MapStruct is using the empty constructor in this case.
All in all - great library, almost perfect for my current usage!