原创 | 使用 JPA 实现 DDD 持久化 -O/R 映射元数据 - 值和关联的比较 + 继承映射

@startuml
abstract class BaseEntity {
  - id: int
  - version: int
}
abstract class Buyer <<Entity>> {
  - name: String
  - mobileNo: String
  - wiredNo: String
  - email: String
}
class OrgBuyer <<Entity>> {
  - businessLicenseNo: String
  - taxNo: String
}
class ContactInfo <<ValueObject>> {
  - name: String
  - gender: Gender
  - mobileNo: String
  - email: String
}
class Address <<ValueObject>> {
  - province: String
  - city: String
  - detail: String
  - receiver: String
  - receiverPhone: String
}
BaseEntity <|- Buyer
Buyer <|- OrgBuyer
Buyer <|- PersonalBuyer
Buyer *--> "shippingAddresses*" Address
OrgBuyer *--> ContactInfo
@enduml

@Entity
@Table(name = "buyers")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(discriminatorType = DiscriminatorType.STRING)
public abstract class Buyer extends BaseEntity {
    private String name;
    private String mobileNo;
    private String wiredNo;
    private String email;
    @ElementCollection
    @CollectionTable(name = "shipping_addresses", joinColumns = @JoinColumn(name = "buyer_id"))
    private Set<Address> shippingAddresses = new HashSet<>();
}
@Entity
@DiscriminatorValue("P")
public class PersonalBuyer extends Buyer {
    @Enumerated(EnumType.STRING)
    private Gender gender;
    @ElementCollection
    @CollectionTable(name = "contact_infos", joinColumns = @JoinColumn(name = "buyer_id"))
    @MapKeyEnumerated(EnumType.STRING)
    @MapKeyColumn(name = "im_type")
    @Column(name = "im_value")
    private Map<ImType, String> imInfos = new HashMap<>();
}
@Entity
@DiscriminatorValue("O")
public class OrgBuyer extends Buyer {
    @Column(name = "business_license_no")
    private String businessLicenseNo;
    private String taxNo;
    @AttributeOverrides({
            @AttributeOverride(name = "name", column = @Column(name = "contact_name")),
            @AttributeOverride(name = "gender", column = @Column(name = "contact_gender")),
            @AttributeOverride(name = "mobileNo", column = @Column(name = "contact_mobile_no")),
            @AttributeOverride(name = "email", column = @Column(name = "contact_email"))
    })
    private ContactInfo contactInfo;
}

@Entity
@Table(name = "orders")
public class Order extends BaseEntity {
    @ManyToOne
    private Buyer buyer;
    public Buyer getBuyer() {
        return buyer;
    }
    public void setBuyer(Buyer buyer) {
        this.buyer = buyer;
    }
}

select b from PersonalBuyer b where b.gender = :gender

select b from OrgBuyer b where b.businessLicenseNo = :businessLicenseNo

select b from Buyer b where name = :name

select o from Order o join o.buyer b where TYPE(b) = OrgBuyer

@MappedSuperclass
public abstract class BaseEntity implements Serializable {
    @Id
    @GeneratedValue
    private int id;
    @Version
    private int version;
    private LocalDateTime created;
    @Column(name = "last_updated")
    private LocalDateTime lastUpdated;
    @Transient
    private boolean isNew = true;
}