What causes unability to fetch entities in this code? - spring

Question

So i'm developing a REST API for my Spring appplication. I have to store all data in H2 database and i'm trying to find a correct way to do so. I'm new to JPA and databases and general and need help understanding the causes of errors here.
First, i have these entities.
Position.java:
package com.example.offerserver.offerservice.task1;
#Entity
#Table(name = "position_table")
public class Position {
public Position() {
}
public Position(UUID id, String name, Integer salary) {
this.id = id;
this.name = name;
this.salary = salary;
}
#Id
private UUID id;
#Column(name = "name")
private String name;
#Column(name = "salary")
private Integer salary;
//getters and setters
Stuff.java:
package com.example.offerserver.offerservice.task1;
#Entity
#Table(name = "stuff_table")
public class Stuff {
public Stuff(){};
public Stuff(UUID id,
String surname,
String name,
String patronymic,
boolean sex,
LocalDate birthDate,
Double salaryMultiplier,
Position position) {
this.id = id;
this.surname = surname;
this.name = name;
this.patronymic = patronymic;
this.sex = sex;
this.birthDate = birthDate;
this.salaryMultiplier = salaryMultiplier;
this.position = position;
}
#Id
private UUID id;
#Column(name="surname")
private String surname;
#Column(name="name")
private String name;
#Column(name="patronymic")
private String patronymic;
#Column(name="sex")
private boolean sex;
#Column(name="birth_date")
private LocalDate birthDate;
#Column(name="salary_multiplier")
private Double salaryMultiplier;
#OneToOne(fetch = FetchType.LAZY)
private Position position;
And JPA repositories:
package com.example.offerserver.repository;
#Repository
public interface StuffRepository extends JpaRepository<Stuff, String> {
}
package com.example.offerserver.repository;
#Repository
public interface PositionRepository extends JpaRepository<Position, UUID> {
}
And i have this request:
package com.example.offerserver.controller;
#Controller
#RequestMapping("/api/v1/stuff")
public class StuffListController {
#Autowired
StuffRepository repository;
#GetMapping("")
public ResponseEntity<List<Stuff>> getStuffList(){
List<Stuff> stuff = repository.findAll();
return new ResponseEntity<>(stuff, HttpStatus.OK);
Sending this request i'm getting this error:
Could not write JSON: Unable to find com.example.offerserver.offerservice.task1.Position with id f0bd15f2-74c1-4979-854b-ffbe44b3da59; nested exception is com.fasterxml.jackson.databind.JsonMappingException: Unable to find com.example.offerserver.offerservice.task1.Position with id f0bd15f2-74c1-4979-854b-ffbe44b3da59 (through reference chain: java.util.ArrayList[0]->com.example.offerserver.offerservice.task1.Stuff["position"]->com.example.offerserver.offerservice.task1.Position$HibernateProxy$E63ZeIxs["id"])
org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: Unable to find com.example.offerserver.offerservice.task1.Position with id f0bd15f2-74c1-4979-854b-ffbe44b3da59; nested exception is com.fasterxml.jackson.databind.JsonMappingException: Unable to find com.example.offerserver.offerservice.task1.Position with id f0bd15f2-74c1-4979-854b-ffbe44b3da59 (through reference chain: java.util.ArrayList[0]->com.example.offerserver.offerservice.task1.Stuff["position"]->com.example.offerserver.offerservice.task1.Position$HibernateProxy$E63ZeIxs["id"])
In debug every instance of stuff in the list is initialized without its "position" field, throwing an error:
Method threw 'javax.persistence.EntityNotFoundException' exception. Cannot evaluate com.example.offerserver.offerservice.task1.Position$HibernateProxy$2ZiRYZbP.toString()
This is how position repository is initialized on launch:
public static List<Position> POSITIONS = List.of(
new Position(UUID.randomUUID(), "Junior Java Backend Developer", 60000),
new Position(UUID.randomUUID(), "Middle Machine Learning Engineer", 120000),
new Position(UUID.randomUUID(), "Senior DevOps Engineer", 200000),
new Position(UUID.randomUUID(), "Senior DevOps Engineer", 150000),
new Position(UUID.randomUUID(), "Intern System Engineer", 20000)
);
positionRepository.saveAll(POSITIONS);
Stuff repository as well. Position field for every stuff instance is randomly chosen from a POSITIONS list.