Hi all,

not sure if I am at the correct place to discuss this problem. I hope so.

I switched to Hibernate 6 with the newest Spring Boot 3.1.0 data-jpa starter. Before using Spring Boot 2.7.11 the following problem was not there.

I use Kotlin here, which maybe makes a difference because of non nullable types.

I have the following in my Entity
@ElementCollection
@CollectionTable(name = "entity_description")
private val descriptionsInternal: MutableList<Description> = mutableListOf()

The Description class looks as follows

@Embeddable
data class Description(

@Column(nullable = false)
@Convert(converter = NonBlankString255AttributeConverter::class)
var desc: NonBlankString255,

@Column(nullable = false)
var order: Int,
)

I use a special AttributeConverter to convert the database string into Objects

sealed class StringAttributeConverter<T : Any>(
private val instanceCreator: (String) -> T,
) : AttributeConverter<T, String>

object NonBlankString255AttributeConverter : StringAttributeConverter<NonBlankString255>(::NonBlankString255)

When selecting the Entity from database with left joining the descriptions, then i got a Kotlin NullPointerException in "convertToEntityAttribute(dbData: String)" because the dbData is null.

My database table for the descriptions is empty and I expect an empty descriptionsInternal list without errors, because I not expect that the converter would be called for a field that is not filled in db. At least this was not the case with an older version.

I could fix it by using

@Convert(converter = *Nullable*NonBlankString255AttributeConverter::class)
var desc: NonBlankString255,

instead of

@Convert(converter = NonBlankString255AttributeConverter::class)
var desc: NonBlankString255,

But this is not really nice, because the desc: NonBlankString255 is still a not nullable Type without Kotlins "?"

Now I only can have Converters which need to handle always nullable values, because of a maybe empty ElementCollection?

Thanks