Hello Moritz Becker, it looks like the error you’re encountering is caused by the attribute converter declaration you’re using: DogListConverter, in your reproducer, implements AttributeConverter<List<Dog>, String>. Since the collection you’re trying to convert is typed as Collection<Dog>, which is not assignable to the converter’s declared{{List<Dog>}} (being a broader type), Hibernate 6 assumes the converter is to be applied to each of the collection’s elements causing the CCE you’re seeing. The correct declaration for your collection converter should be DogListConverter implements AttributeConverter<Collection<Dog>, String>, that will work correctly. Let me know if you have any doubts or additional comments. |