Adding records to junction table JPA - mysql

Question

I have problem with adding records to my junction table with JPA+Hibernate
when I try to add simple record with POST request it's throws me an error:
"message": "could not execute statement; SQL [n/a]; constraint [null]; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement"
And in my console:
MySQLIntegrityConstraintViolationException: Cannot add or update a child row: a foreign key constraint fails*
I had defined Join columns #JoinColumn(insertable=false, updatable=false) because it was demanding by Hibernate, otherwise it throws me an error that I should do that...
Here is my junction entity code:
#Entity
#Table(name = "hospital_doctor")
#IdClass(Hosdoc.class)
public class HospitalDoctor implements Serializable {
#Id
private int hospitalId;
#Id
private int doctorId;
// fields of hospitalDoctor table
#Temporal(TemporalType.DATE)
private Date contractStartDate;
#Temporal(TemporalType.DATE)
private Date contractEndDate;
private String position;
private String supervisor;
private boolean partTime;
#ManyToOne
#JoinColumn(name="HospitalId", insertable = false, updatable = false)
private Hospital hospital;
#ManyToOne
#JoinColumn(name="DoctorId", insertable = false, updatable = false)
private Doctor doctor;
// GETTERS AND SETTERS....
I wrote simple adding function in hospital class but I don't know how to use it to add record to junction table by POST request.
public void addDoctor(Doctor doctor, boolean partTime, Date contractEndDate, Date contractStartDate,
String position, String supervisor) {
HospitalDoctor association = new HospitalDoctor();
association.setDoctor(doctor);
association.setHospital(this);
association.setDoctorId(doctor.getId());
association.setHospitalId(this.getId());
association.setContractStartDate(contractStartDate);
association.setContractEndDate(contractEndDate);
association.setPosition(position);
association.setSupervisor(supervisor);
association.setPartTime(partTime);
doctors.add(association);
}
Service:
public void addHospitalDoctor(HospitalDoctor hospitalDoctor) {
hospitalDoctorDao.save(hospitalDoctor);
}
Controller:
#PostMapping(value = "/api/hospitaldoctors")
public void addHospitalDoctor(HospitalDoctor hospitalDoctor) {
hospitalDoctorService.addHospitalDoctor(hospitalDoctor);
}