apa itu @JoinColumn dan bagaimana menggunakannya di Hibernate

Asosiasi searah melalui tabel gabungan

@Entity
class Patient {

    @OneToMany
    private Collection<Vehicle> vehicles = new ArrayList<Vehicle>();

}

@Entity
class Vehicle {

}

Asosiasi dua arah melalui tabel gabungan

@Entity
class Patient {

    @OneToMany
    private Collection<Vehicle> vehicles = new ArrayList<Vehicle>();

}

@Entity
class Vehicle {

    @ManyToOne(fetch = FetchType.LAZY)
    private Patient patient;

}

Asosiasi searah melalui kunci asing

@Entity
class Patient {

    @OneToMany
    @JoinColumn
    private Collection<Vehicle> vehicles = new ArrayList<Vehicle>();

}

@Entity
class Vehicle {

}

Asosiasi dua arah melalui kunci asing

@Entity
class Patient {

    @OneToMany(mappedBy = "patient")
    private Collection<Vehicle> vehicles = new ArrayList<Vehicle>();

}

@Entity
class Vehicle {

    @ManyToOne(fetch = FetchType.LAZY)
    private Patient patient;

}

Asosiasi dua arah melalui kunci asing dengan spesifikasi nama kolom asing

@Entity
class Patient {

    @OneToMany(mappedBy = "patient")
    private Collection<Vehicle> vehicles = new ArrayList<Vehicle>();

}

@Entity
class Vehicle {

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name="patient_id")
    private Patient patient;

}

Ini adalah titik awal dasar menggunakan @JoinColumn .

Untuk memverifikasi bahwa kunci asing(patient_id di Vehicle table) benar-benar dipetakan di tabel pasien, Anda dapat menggunakan @JoinColumn(nullable = false)

@Entity
class Vehicle {

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name="patient_id", nullable = false)
    private Patient patient

}