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Allow Supertypes Specifications in JpaSpecificationExecutor #3300

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aykborstelmann opened this issue Jan 4, 2024 · 5 comments · May be fixed by #3301
Open

Allow Supertypes Specifications in JpaSpecificationExecutor #3300

aykborstelmann opened this issue Jan 4, 2024 · 5 comments · May be fixed by #3301
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@mp911de
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for: team-attention An issue we need to discuss as a team to make progress status: waiting-for-triage An issue we've not yet triaged

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@aykborstelmann
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aykborstelmann commented Jan 4, 2024 •
edited

See the following commit: 4c45125
I added a test in your codebase which is exactly the same as I am going to describe.

Suppose we have an abstract @MappedSupperclass AbstractMappedType and a concrete entity ConcreteType1 extending AbstractMappedType.

Then we also have MappedTypeRepository which is a @NoRepositoryBean but does extend JpaSpecificationExecutor and must therefore look like this:

@NoRepositoryBean
public interface MappedTypeRepository<T extends AbstractMappedType> extends JpaRepository<T, Long>, JpaSpecificationExecutor<T> {
}

However when using this repository in its abstract form, we face some issues.

@Autowired
@Qualifier("concreteRepository1")
private MappedTypeRepository<?> mappedTypeRepository;

@Test
void testUseMappedTypeRepository() {
  concreteRepository1.save(new ConcreteType1("Test"));

  List<? extends AbstractMappedType> findings = mappedTypeRepository.findAll(
      where(mappedTypeAttribute1Equals("Test")));
  assertThat(findings).isNotEmpty();
}

private static Specification<AbstractMappedType> mappedTypeAttribute1Equals(String attribute1) {
  return (root, query, criteriaBuilder) -> criteriaBuilder.equal(root.get(AbstractMappedType_.ATTRIBUTE1), attribute1);
}

This does not work because Specification<AbstractMappedType> cannot be applied as first parameter for
List<T> findAll(Specification<T> spec); of JpaSpecificationExecutor<T>.

IMO, the method JpaSpecificationExecutor#findAll should be defined as follows, accepting also specifications of supertypes of T.

List<T> findAll(Specification<? super T> spec);

In fact, I have already implemented change, and you can have a look at #3301
@aykborstelmann aykborstelmann linked a pull request Jan 4, 2024 that will close this issue
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@spring-projects-issues spring-projects-issues added the status: waiting-for-triage An issue we've not yet triaged label Jan 4, 2024
@christophstrobl christophstrobl added the for: team-attention An issue we need to discuss as a team to make progress label Jan 9, 2024
@christophstrobl
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@aykborstelmann thank you for getting in touch. Let me take this to the team.

@mp911de mp911de self-assigned this Jan 22, 2024
@aykborstelmann
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@christophstrobl Thanks for taking care. Any updates on this ?

@aykborstelmann
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Hi, once again, any updates on it ?
I already provided you an PR (#3301) which implements the change :)

@mp911de
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mp911de commented Apr 22, 2024

For the time being, this looks like a wall of changes without providing an immediate benefit. As we don't have much bandwidth, this isn't something we will incorporate soon. We might revisit your proposal next year or so.

@aykborstelmann
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Alright, thank you for the answer!

I hope I could motivate the benefits enough with the given example and test, if not please let me know !
Currently any usage of JpaSpecificationExecutor in a generic repository have to be faced with hacky solutions such as wildcards in returns types and unchecked castings. I have faced this issue in many projects until now.
Hopefully the passing tests can somehow ensure you valid working state of the PR.

I am looking forward to a diskussion then :)

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Allow Supertypes Specifications in JpaSpecificationExecutor aykborstelmann/spring-data-jpa
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@mp911de @christophstrobl @spring-projects-issues @aykborstelmann