How do I create a mapper from entity to dto, where dto is nested? - spring

Question

Two entities with corresponding dtos are given
entities:
class GalleryBlock(
var images: List<Image?>,
override val sortIndex: Int = 0,
) : ArticleBlock(sortIndex)
class Image(
var url: String,
var imageSize: ImageSize,
override var id: Long,
override var lastModified: Date,
override var lastModifiedBy: String? = null ) : DBEntity
enum class ImageSize {
SMALL,
MEDIUM,
LARGE, }
dtos
data class GalleryBlockDto(
var images: List<ImageDto>,
override val sortIndex: Int,
) : ArticleBlockDto
data class ImageDto(
var id: Long,
var url: String,
var imageSize: ImageSize,
)
for the mapping I have written an interface Mapper
interface Mapper<E, D> {
fun fromEntity(entity: E): D
}
for the mapping from class Image to ImageDto I have create a class ImageMapper
#Component
class ImageMapper: Mapper<Image, ImageDto> {
override fun fromEntity(entity: Image): ImageDto {
return ImageDto(entity.id, entity.url, entity.imageSize)
}
}
when mapping the GalleryBlock I did the same but I get a type mismatch.
#Component
class GalleryBlockMapper: Mapper<GalleryBlock, GalleryBlockDto> {
override fun fromEntity(entity: GalleryBlock): GalleryBlockDto {
val images = entity.images
val sortIndex = entity.sortIndex
return GalleryBlockDto(images, sortIndex)
}
}
is my approach correct? and how do I get the type mismatch fixed without changing the fields of Dto and entities?

Answer 1

In your GalleryBlockMapper you pass Image instances to the GalleryBlockDto. But ImageDto instances are needed. The ImageMapper needs to be injected into the GalleryBlockMapper, so the images can be mapped.
#Component
class GalleryBlockMapper(private val imageMapper: ImageMapper): Mapper<GalleryBlock, GalleryBlockDto> {
override fun fromEntity(entity: GalleryBlock): GalleryBlockDto {
val images = entity.images.map { imageMapper.fromEntity(it) }
val sortIndex = entity.sortIndex
return GalleryBlockDto(images, sortIndex)
}
}