QueryDSL-JPA + Custom type implementing Number + NumberExpression

[HonoluluHenk]

Observed vs. expected behavior

When using the following Combination

• a custom Type extending Number, converted using JPA @Converter/AttributeConverter (also happens with all other Hibernate custom types like UserType)
• a NumberExpression in the JPAQuery like sum()

Example:

var rows = new JPAQuery<>(em)
		.select(myEntity.myCustomNumber.sum())
		.from(myEntity)
		.fetch();

Actual outcome:
I receive java.lang.IllegalArgumentException: Unsupported target type : MyCustomNumber instead of a valid result.

Expected outcome:
The query-result.

Steps to reproduce

I created a reproducer with unit tests showing what works and what doesn't:
https://github.com/dvbern/bug-reproducers-querydsl-jpa-hibernate6

Environment

Querydsl version: 5.0.0-jakarta (does not look like a jakarta-problem, though)

Querydsl module: querydsl-jpa/querydsl-core

Database: any (e.g. hsqldb, postgresql)

JDK: 17 (but the stacktrace indicates this is not a JDK-problem)

Additional details

Works correctly - at least "as expected" :) - in the old Hibernate 5.

(Edit: QueryProjection and Hibernate6 is not necessary. I updated Description + Title accordingly)

[jwgmeligmeyling]

I’m not so sure if Converters ever “worked as intended” for Hibernate 5 as well: #2652

The problem is that the JPA specification doesnt really specify how converted fields should be treated in JPQL, leading to different expectations and implementations in JPA vendors.

[velo]

Hi,

I have forked this project and we just released a released a milestone to maven central that is compatible with hibernate 6.
https://repo1.maven.org/maven2/io/github/openfeign/querydsl/querydsl-core/6.0.0.M1/

If you can, please try 6.0.0.M1 and let us know how it goes.

Also note the artifact GAV changed:

    <dependency>
      <groupId>io.github.openfeign.querydsl</groupId>
      <artifactId>querydsl-jpa</artifactId>
      <version>6.0.0.M1</version>
    </dependency>

[HonoluluHenk]

I just tried your fork and switched from foo.sum() to foo.sumAggregate() and ran into the exact same error.
Your fork provides foo.sumBigDecimal which is at least a working workaround.

Would you like me to continue this bug-report on your forked repo?

[velo]

Yes please

[HonoluluHenk]

Discussion continued on the OpenFeign issue

[HonoluluHenk]

To all coming here from google: the bug is not related to Hibernate 6 but a custom type somehow implementing Number