Hibernate JPA Case expression handling problem

Hibernate ORM
1

In a JPA query with single item select list, if a case expression with entity result is used, the result of query is a list of empty arrays instead of a list of objects. for example if I have an entity named PersonalActor and have 10 records of data in database, the following query return a list that its size equals 10 and its content is empty array.

select case when pa.name = 'a1' then pa else pa end from PersonalActor pa

the above query may seams somehow meaningless but note that it is just to show the problem.

test environment :

  • jdk 17

  • Hibernate 5.4.24.Final

  • JPA 2.1

to bring about the problem, a test case is created at GitHub - horakhsh/hibernate-test-case-templates: Templates and examples to report issues to Hibernate

thanks

2

This kind of query is illegal. You can only have scalar values in the result arms of case expressions, so if there is a bug, then it would be that we don’t throw an error during query parsing. I believe this is handled properly in Hibernate 6+ though, but the parser in Hibernate 5 is doing some weird stuff which might allow this kind of query to parse successfully, but produce rubbish results.