Hibernate JPA：传递给持久化的分离实体

Question

The model contains:

StationSecondaire class :

@ManyToOne(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
@JoinColumn(name = "station_principal_id", nullable = false)
public StationPrincipale getStationPrincipale() {
    return this.stationPrincipale;
}

and StationPrincipale class :

@OneToMany(cascade = CascadeType.ALL,fetch = FetchType.LAZY, mappedBy = "stationPrincipale")
public Set<StationSecondaire> getStationSecondaires() {
    return this.stationSecondaires;
}

And i tried to obtain an existent StationPrincipale in database by:

StationPrincipale sp = spDAO.findStationByName("Some name");
//Some staff
StationSecondaire ssNew = new StationSecondaire(0, ((Station) obj).getValue().toString(), null,((Station) obj).getId());
ssNew.setStationPrincipale(sp); 

//staff
ssDAO.persist(ssNew);

After that, I created some new StationSecondaire object and I attached them to the sp .

When i tried to persist StationSecondaire object, i got that error :

detached entity passed to persist: StationPrincipale

How can i fix it so that i can add an StationSecondaire object attached to an existent StationPrincipale one?

Answer 1

persist是新值，因此使用merge而不是它，因为sp已经存在。