Attribute converter not "comparable" (YearMonth scenario)


I recently migrated a project to SpringBoot 3.0.3 / Hibernate 6.1.7
The model has java.time.YearMonth attributes being mapped to integers on the DB (MariaDB)

Here is how it was used:

@Convert(converter = YearMonthConverter.class)
@Column(name = "month", nullable = false)
private YearMonth month;

And here is the converter class (based on Jakarta now):

public class YearMonthConverter implements AttributeConverter<YearMonth, Integer> {
    public Integer convertToDatabaseColumn(YearMonth attribute) {
        return attribute == null ? null : (attribute.getYear() * 100) + attribute.getMonth().getValue();

    public YearMonth convertToEntityAttribute(Integer dbData) {
        return dbData == null ? null : YearMonth.of(dbData / 100, dbData % 100);

I’ve got a MAX() query on this column which fails with the following error:
org.hibernate.QueryException: Parameter 1 of function max() has type COMPARABLE, but argument is of type java.time.YearMonth

I’ve tried multiple things, debugging in the hibernate core classes to find ideas / solutions:

  • Defining a YearMonthJavaType extends AbstractClassJavaType<YearMonth> based on the other time-related classes defined in Hibernate core, and registering it with @JavaTypeRegistration(javaType = YearMonth.class, descriptorClass = YearMonthJavaType.class)
  • Creating a YearMonthUserType implements UserType<YearMonth> applied on my attribute with @Type(value = YearMonthUserType.class)

It’s worth noticing that the ORM is able to read/write this column from the DB, it only fails to run functions like MIN or MAX.

The debugging took me to a section of the code in ArgumentTypesValidator where the code considers that the node type YearMonth is a VarbinaryTypeDescriptor and so incompatible with the FunctionParameterType COMPARABLE.

I’m running out of ideas, so any help would be appreciated


That’s a bug. Please create a JIRA issue for this.

Thank you, I created this Jira ticket: [HHH-16241] - Hibernate JIRA and added a demo project reproducing the errors