如何使用 jpa 注釋和存儲庫實現具有 2 個實體作為主鍵的實體

Question

我想與其中的數量信息實現多對多關聯。 像這樣：

@Entity
@Table(name = "reserves")
@Getter @Setter @NoArgsConstructor
public class Reserve {
    @Id
    @ManyToOne(cascade = CascadeType.ALL,fetch = FetchType.EAGER)
    @JoinColumn(name = "groupe_id")
    private GroupeSanguin bloodGroup;
    @Id
    @ManyToOne(cascade = CascadeType.ALL,fetch = FetchType.EAGER)
    private Banque banque;
    private int quantity;
}

GroupSanguin 和 Banque 是兩個 class 存儲在數據庫中的兩個。 如果需要，這是兩者的代碼：

@Entity
@Table(name = "groupe_sanguins")
public class GroupeSanguin {
    @Id
    private String groupe;
    @OneToMany(mappedBy = "groupeSanguin")
    private List<Donneur> donneurs;
}
@Entity @Getter @Setter @NoArgsConstructor
public class Banque {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    @Column(unique = true,nullable = false)
    private String nom;
    private String adresse;
    @Column(unique = true)
    private String telephone;
    private String localisation;
}

所以我想知道如何注釋 JpaRepository 以將兩者作為主鍵，我的注釋是否適合它工作？

public interface ReserveRepository extends JpaRepository<
Reserve,
//what to put here ?
>

Answer 1

實際上，這不是 JPA 問題，而是關系數據庫概念。 如果 Reserve 有自己的數據並與其他實體鏈接它有自己的 Id您可以添加唯一性約束

@Entity
@Table(name = "reserves", uniqueConstraints={
@UniqueConstraint(columnNames = {"banque_id", "groupe_id"})
@Getter @Setter @NoArgsConstructor
public class Reserve {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
   

@ManyToOne(cascade = CascadeType.ALL,fetch = FetchType.EAGER)
@JoinColumn(name = "groupe_id")
private GroupeSanguin bloodGroup;
   
@ManyToOne(cascade = CascadeType.ALL,fetch = FetchType.EAGER)
@JoinColumn(name = "banque_id")
private Banque banque;
private int quantity;

}

Answer 2

我也找到了這個解決方案。

@Entity
@Table(name = "reserves")
@Getter @Setter @NoArgsConstructor
@IdClass(ReserveId.class) //this annotation will tell that id that the 
// the id will be represented by a class
public class Reserve {
    @Id
    @ManyToOne(cascade = CascadeType.ALL,fetch = FetchType.EAGER)
    @JoinColumn(name = "groupe_id")
    private GroupeSanguin groupeSanguin;
    @Id
    @ManyToOne(cascade = CascadeType.ALL,fetch = FetchType.EAGER)
    @JoinColumn(name = "banque_id")
    private Banque banque;
    private int quantity;
}

並且 id class 應該像這樣實現 Serializable ：

@Getter @Setter
public class ReserveId implements Serializable {
    private Banque banque;
    private GroupeSanguin groupeSanguin;
}

最后存儲庫將是這樣的：

@Repository
public interface ReserveRepo extends JpaRepository<Reserve, ReserveId>{}

Answer 3

查看您的 Reserve class 沒有提到復合主鍵。 首先你需要修復model，你可以參考這里的解決方案How to create and processing composite primary key in JPA