Hibernate如何区分对象类型和InheritanceType.Joined

Question

我在Spring应用程序中有不同的用户类型。我实现了某种继承。所有users类型都从User类扩展而来。我想这里两张桌子应该够了：

1. 表“users”-包含所有共享实体属性的列
2. 表“users_corporate”-包含CorporateCustomer类attriburtes:companyName和VatNumber的列

“用户”将具有:id、用户名、密码、第一名、最后名、电子邮件、手机、城市、街道、邮政编码

BaseEntity：

@MappedSuperclass
public class BaseEntity{

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;
}

用户：

@Entity
@Table(name="users")
@Inheritance(strategy = InheritanceType.JOINED)
public class User extends BaseEntity{

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

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

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

    @ManyToMany(fetch = FetchType.EAGER)
    @JoinTable(name = "users_roles", joinColumns = @JoinColumn(name = "user_id"), inverseJoinColumns = @JoinColumn(name = "role_id"))
    private Collection<Role> roles;

}

CorporateCustomer：

@Entity
@Table(name="users_corporate")
public class CorporateCustomer extends User{

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

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

    @OneToMany(mappedBy = "customer")
    private List<Appointment> appointments;
}

@Entity
//@Table  <---- i think it is not needed here?
public class RetailCustomer extends User {

    @OneToMany(mappedBy = "customer")
    private List<Appointment> appointments;
}

@Entity
//@Table  <---- i think it is not needed here?
public class Provider extends User{

    @OneToMany(mappedBy = "provider")
    private List<Appointment> appointments;

    @ManyToMany
    @JoinTable(name="works_providers", joinColumns=@JoinColumn(name="id_user"), inverseJoinColumns=@JoinColumn(name="id_work"))
    private List<Work> works;

    @OneToOne(mappedBy="provider", cascade = {CascadeType.ALL})
    private WorkingPlan workingPlan;
}

Answer 1

如果Provider和RetailCustomer的类中没有@Table注释，hibernate将如何区分它们？

如果不使用@table指定表名，则表名将与实体名相同。

当我调用ProviderRepository.findAll（）时，它现在将如何从“Users”表中哪些行是provider，哪些行是RetailCustomer？

select ... from Provider p
inner join User u on p.id=u.id

select ..., 
case 
when r.id is not null then 1 
when p.id is not null then 2 
when u.id is not null then 0 
end as clazz_0_ 
from User u
left outer join Provider p on p.id=u.id 
left outer join RetailCustomer r on r.id=u.id