Question

我有三个表，每个表都映射到其中一个实体。 “已分配”表充当“用户”和“角色”之间的关系，每个表都有一个外键。我如何在我的实体上映射它，以便我可以从UserEntity获取一组EntityRoles？我无法弄清楚如何使这项工作。这甚至可能吗？

@Entity
@Table(name = "users")
public class UserEntity {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name="user_id")
    private long id;

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


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

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

    //I want to be able to get a set of RoleEntities
    @OneToMany(fetch = FetchType.LAZY, mappedBy = "id")
    private Set<RoleEntity> roles;
}



@Entity
@Table(name = "assigned")
public class AssignedEntity implements Serializable {

    @Id
    //@Column(name = "assigned_role")
    @ManyToOne(targetEntity = RoleEntity.class, fetch = FetchType.LAZY)
    @JoinColumn(name = "fk_role")
    private long roleId;

    @Id
    //@Column(name = "assigned_user")
    @ManyToOne(targetEntity = UserEntity.class, fetch = FetchType.LAZY)
    @JoinColumn(name = "fk_user")
    private long userId;
}

@Entity
@Table(name = "roles")
public class RoleEntity implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name="role_id")
    @OneToOne(fetch = FetchType.LAZY, mappedBy="roleId")
    private long id;

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

Answer 1

您使用的是不正确/不方便的映射。始终尽可能简单地保持事物。

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持久性提供程序将为您创建（有效）连接表。您可以使用@Entity @Table(name = "users") public class User { @Id @GeneratedValue private Long id; @ManyToMany(fetch = FetchType.LAZY) private List<Role> roles; } @Entity @Table(name = "roles") public class Role { @Id private Long id; @Column private String name; }注释指定连接表的名称。此外，您还需要考虑@JoinTable实体的id的自动生成值：Role表类似于参考数据表。因此，您可能需要对roles值进行硬编码。

获取用户角色（在持久化上下文中）：

id

JPA两个实体一个关系：我如何获得通过关系链接的实体集？

1 个答案: