How to define a unidirectional OneToMany JPA relationship without any cascade?

Question

When I try to save person, it doesn't save anything neither person nor city. I don't want to save or update City objects. I just want to update/remove joinColumn. Is there any way to do this?

Person person = new Person();
person.setCities(...);
personDAO.save(person);



public class Person{

    @OneToMany(fetch = FetchType.EAGER)
    @JoinColumn(name = "city_id")
    private List<City> cities;

}


public class City{
    @Id
    @Column(name = "city_id")
    @GeneratedValue(generator = "system-uuid")
    @GenericGenerator(name = "system-uuid", strategy = "org.hibernate.id.UUIDGenerator")
    private String cityId;

}

Answer 1

First define the @ManyToOne mapping on the City side:

@ManyToOne
@JoinColumn(name = "person_id")
private Person person;

Then add mappedBy attribute and remove @JoinColumn:

@OneToMany(fetch = FetchType.EAGER, mappedBy = "person")
private List<City> cities;

and when you save / update you have to set the entities on both sides of the dependency:

Person person = new Person();
person.setCities(...);

for(City city: cities){
   city.setPerson(person);
}  

personDAO.save(person);

The same goes for removal.. you have to remove the entity references on both sides.