Spring-Data-JPA atomic insert with dependencies - spring

Question

I want to insert Entities to a database from a scalable microservice. I tried #Lock(LockModeType.PESSIMISTIC_WRITE) to prevent from doubled entries. The problem is, I have dependencies on my Entities.
A basic example is:
TestEntity.java
public class TestEntity {
#GeneratedValue()
#Id
private Long id;
private String string;
#ManyToOne
private TestEntityParent testEntityParent;
}
TestEntityParent.java
public class TestEntityParent {
#GeneratedValue()
#Id
private Long id;
private String stringTwo;
#OneToMany(mappedBy = "testEntityParent")
private List<TestEntity> testEntities;
}
TestEnityRepository.java
public interface TestEnityRepository extends JpaRepository<TestEntity,Long> {
#Lock(LockModeType.PESSIMISTIC_WRITE)
TestEntity saveAndFlush(TestEntity testEntity);
Optional<TestEntity> findByStringAndTestEntityParentStringTwo(String string, String stringTwo);
}
TestEntityParentRepository.java
public interface TestEntityParentRepository extends JpaRepository<TestEntityParent, Long> {
#Lock(LockModeType.PESSIMISTIC_WRITE)
TestEntityParent save(TestEntityParent testEntityParent);
Optional<TestEntityParent> findByStringTwo(String stringTwo);
}
AtomicDbService.java
#Service
public class AtomicDbService {
#Autowired
TestEnityRepository testEnityRepository;
#Autowired
TestEntityParentRepository testEntityParentRepository;
#Transactional
public TestEntity atomicInsert(TestEntity testEntity) {
TestEntityParent testEntityParent = testEntityParentRepository.findByStringTwo(testEntity.getTestEntityParent().getStringTwo())
.orElse(testEntityParentRepository.save(testEntity.getTestEntityParent()));
return testEnityRepository.findByStringAndTestEntityParentStringTwo(
testEntity.getString(), testEntity.getTestEntityParent().getStringTwo()
).orElse(testEnityRepository
.save(
TestEntity.builder()
.string(testEntity.getString())
.testEntityParent(testEntityParent)
.build()
)
);
}
}
My test case:
#Test
#Transactional
public void testAtomicInsert(){
TestEntityParent testEntityParent = TestEntityParent.builder().stringTwo("testTwo").build();
TestEntity testEntity = TestEntity.builder().string("test").testEntityParent(testEntityParent).build();
atomicDbService.atomicInsert(testEntity);
System.out.println(testEnityRepository.findAll());
atomicDbService.atomicInsert(testEntity);
System.out.println(testEnityRepository.findAll());
atomicDbService.atomicInsert(testEntity);
System.out.println(testEnityRepository.findAll());
System.out.println(testEnityRepository.findAll());
}
I get the following answer:
[TestEntity(id=2, string=test, testEntityParent=TestEntityParent(id=1, stringTwo=testTwo, testEntities=null))]
[TestEntity(id=2, string=test, testEntityParent=TestEntityParent(id=1, stringTwo=testTwo, testEntities=null)), TestEntity(id=3, string=test, testEntityParent=TestEntityParent(id=1, stringTwo=testTwo, testEntities=null))]
and an error:
query did not return a unique result: 2;
Without dependencies everything works fine.
UPDATE:
Adding #Lock(LockModeType.PESSIMISTIC_WRITE) to the find method leads to
Feature not supported: "MVCC=TRUE && FOR UPDATE && JOIN"; SQL statement:
... same applies to
#Lock(LockModeType.PESSIMISTIC_WRITE)
#Query("SELECT e from TestEntity e join e.testEntityParent p where e.string = :string and p.stringTwo = :stringTwo ")
Optional<TestEntity> findWhatever(#Param("string") String string, #Param("stringTwo") String stringTwo);
... since for update is always generated.

Answer 1

Apparently, it was a stupid mistake I needed to replace orElse with orElseGet and a lambda and everything worked, even without all those #Lock, etc - tricks.
Still I don't understand what exactly went wrong with the transactions and why.