Why is there a loop in #OneToMany mapping? - jpa

Question

I am trying to create a #OneToMany database using JPA. There is a object Flight and a object Passenger.
the code:
#Entity
#Table(name = "passengers")
public class Passenger {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private long id;
#Column(name = "name")
private String name;
#Column(name = "surname")
private String surname;
private String email;
private String phoneNumber;
private String birthDate;
#ManyToOne(optional = false)
#JoinColumn(name = "flight_id")
private Flight flight;
public Passenger() {
}
public Passenger(String name, String surname, String email, String phoneNumber, String birthDate, Flight flight) {
super();
this.name = name;
this.surname = surname;
this.email = email;
this.phoneNumber = phoneNumber;
this.birthDate = birthDate;
this.flight = flight;
}
#Entity
#Table(name = "flights")
public class Flight {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "flight_id")
private long id;
private String departure;
private String destination;
private String date;
private int capacity;
private float price;
#OneToMany(fetch = FetchType.EAGER, mappedBy = "flight", cascade = CascadeType.ALL)
private Set<Passenger> passengers;
public Flight() {
}
public Flight(String departure, String destination, String date, int capacity, float price) {
super();
this.departure = departure;
this.destination = destination;
this.date = date;
this.capacity = capacity;
this.price = price;
}
this is how I add a new Passenger:
#PostMapping("/flights")
public ResponseEntity<Object> updateFlight(#RequestBody Flight flight) {
long id = flight.getId();
Optional<Flight> flightOptional = flightRepository.findById(id);
if (!flightOptional.isPresent())
return ResponseEntity.notFound().build();
int currentCapacity = flight.getCapacity();
flight.setCapacity(currentCapacity - 1);
for(Passenger passenger : flight.getPassengers()) {
System.out.println(passenger.getName());
}
this.flightRepository.save(flight);
return ResponseEntity.noContent().build();
}
Unfortunately, when I map the flights and passengers, I appear to have a never ending loop. Passengers have the details of the flight and passengers and again flight and then passengers, and so on.
Is there any way I can resolve it? Am I missing anything?

Answer 1

To avoid the cyclic problem Use #JsonManagedReference, #JsonBackReference as below.
Add #JsonManagedReference on Parent class
#JsonManagedReference
#OneToMany(fetch = FetchType.EAGER, mappedBy = "flight", c
ascadee = CascadeType.ALL)
private Set<Passenger> passengers;
Add #JsonBackReference on child class as below
#JsonBackReference
#ManyToOne(optional = false)
#JoinColumn(name = "flight_id")
private Flight flight;