@Entity
@Table(name = "stage")
public class Stage extends AbstractEntity {

    @Column(name = "name")
    private String name;

    @Column(name = "color")
    private String color;

    @Column(name = "`default`")[SRC java]

    private boolean byDefault;

    @OneToMany(mappedBy = "stage", fetch = FetchType.LAZY)
    private List<StageContact> stageContacts = new ArrayList<>();

    public Stage() {}

    public List<StageContact> getStageContacts() {
        return stageContacts;
    }

    public void setStageContacts(List<StageContact> stageContacts) {
        this.stageContacts = stageContacts;
    }
}

@Entity
@Table(name = "contact")
public class Contact extends AbstractEntity {

    @Column(name = "urlName")
    private String urlName;

    @Column(name = "name")
    private String name;

    @Column(name = "email")
    private String email;

    @Column(name = "url")
    private String url;

    @Column(name = "avatar")
    private String avatar;

    @Column(name = "type")
    private String type;

    @Column(name = "headline")
    private String headline;

    @Column(name = "company")
    private String company;

    @Column(name = "school")
    private String school;

    @Column(name = "location")
    private String location;

    @Column(name = "currency")
    @Enumerated(EnumType.STRING)
    private Currency currency;

    @JsonIgnore
    @OneToMany(mappedBy = "contact", fetch = FetchType.LAZY)
    private List<StageContact> stageContacts = new ArrayList<>();

    @PrePersist
    protected void onCreate() {
        super.onCreate();
    }

    public Contact() {}

}

@Entity
@Table(name = "stageContact")
public class StageContact implements Serializable {

    @Id
    @ManyToOne(fetch = FetchType.LAZY)
    @MapsId("stageId")
    @JoinColumn(name = "stageId", referencedColumnName = "id")
    private Stage stage;

    @Id
    @ManyToOne(fetch = FetchType.LAZY)
    @MapsId("contactId")
    @JoinColumn(name = "contactId", referencedColumnName = "id")
    private Contact contact;

    @Column(name = "price")
    private double price;

    public StageContact() {
    }

}