Spring boot JSON return infinite nested objects - spring-boot

Question

I have the following in my code:
CompanyEntity
#Entity
#Table(name = "company")
public class Company{
#OneToMany(mappedBy = "company", cascade = CascadeType.ALL)
#JsonUnwrapped
private Set<User> users;
}
UserEntity
#Entity
#Table(name="user")
public class User{
#ManyToOne(cascade = CascadeType.REFRESH)
#JoinColumn(name="company_id")
private Company company;
}
CompanyController
#GetMapping("/company")
public ResponseEntity<Object> getAllCompanies(){
List<Company> allCompanies = companyService.findAll();
return ResponseEntity.ok(allCompanies);
}
problem is when i call /company in the browser i am getting the users object including the company object. something like this
[
{
"id": 1,
"name": "company",
"users": [
{
"id": 14,
"firstName": "Yamen",
"lastName": "Nassif",
"company": {
"id": 1,
"name": "company",
"users": [
{
"id": 14,
"firstName": "Yamen",
"lastName": "Nassif",
"company": {
"id": 1,
"name": "company",
"users": [
...
same goes when i getAllUsers companies and users are also exanding.
my database looks just fine.
and its endless and of course Stackoverflow error is in the console. How can i fix this ?

Answer 1

You have this error because of the infinite recursion.
Company has a link on User and User has a link on Company.
You have at least two options:
use #JsonManagedReference and #JsonBackReference annotation on the relation fields.
create a pair of DTOs and fill them manually with data from you entities.
e.g.
#GetMapping("/company")
public ResponseEntity<Object> getAllCompanies() {
List<Company> allCompanies = companyService.findAll();
List<CompanyDto> allCompanyDtoList = convertToCompanyDtoList(allCompanies);
return ResponseEntity.ok(allCompanyDtoList );
}
Personally, I'd prefer the second option, since returning Entities is NOT a good practice.

Answer 2

You can use #JsonIgnore annotation to prevent this type of behavior. This usually happens with bidirectional mapping within your entities. It is caused by infinite recursion.
#Entity
#Table(name="user")
public class User{
#ManyToOne(cascade = CascadeType.REFRESH)
#JoinColumn(name="company_id")
#JsonIgnore
private Company company;
}