如何使用 jpa 注释和存储库实现具有 2 个实体作为主键的实体

Question

我想与其中的数量信息实现多对多关联。 像这样：

@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 是两个 class 存储在数据库中的两个。 如果需要，这是两者的代码：

@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释 JpaRepository 以将两者作为主键，我的注释是否适合它工作？

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

Answer 1

实际上，这不是 JPA 问题，而是关系数据库概念。 如果 Reserve 有自己的数据并与其他实体链接它有自己的 Id您可以添加唯一性约束

@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

我也找到了这个解决方案。

@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;
}

并且 id class 应该像这样实现 Serializable ：

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

最后存储库将是这样的：

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

Answer 3

查看您的 Reserve class 没有提到复合主键。 首先你需要修复model，你可以参考这里的解决方案How to create and processing composite primary key in JPA