JPA继承类型。JOINED如何编写父类的关系实体

Question

我有一个母公司类别（工具），有三个子公司（股票、债券、Etf）。父类还与类（InstrumentPrice）有一个OneToMany关系。JPA联接策略用于父实体和子实体之间。当一个子项被持久化（例如Stock）时，工具中的一个条目也会自动持久化，并具有所有公共属性。这很好用。但是，如何为类InstrumentPrice创建条目？我是否必须在保存股票后从DB读取实体工具，并使用InstrumentPrice更新工具？

@MappedSuperclass
public abstract class BaseEntity implements Serializable {

    @Id
    @Column(name = "id")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    protected int id;

}

父类工具

@Entity
@Inheritance(strategy = InheritanceType.JOINED)
@DiscriminatorColumn(name = "instr_type", discriminatorType = DiscriminatorType.STRING, length = 1)
@Table(name = "instrument")

public class Instrument extends BaseEntity {

    @Column
    private String symbol;

    @Column
    private String isin;

    @Column
    private String name;

    @Column
    private boolean active;

    @OneToMany(mappedBy = "instrument", fetch = FetchType.LAZY, cascade = CascadeType.ALL)
    private List<InstrumentPrice> instrumentPriceList;

    // public getters & setters
    ....

类仪器价格

@Entity
@Table(name = "instrumentprice")
public class InstrumentPrice extends BaseEntity {

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "instrument_id", nullable = false)
    private Instrument instrument;

    @Column
    private LocalDate date;
    @Column
    private double open;
    @Column
    private double high;
    @Column
    private double low;
    @Column
    private double close;
    @Column
    private long volume;

    // public getters & setters
    ....

子类库存

@Entity
@DiscriminatorValue("S")
@PrimaryKeyJoinColumn(name = "id")
@Table(name = "stock")
public class Stock extends Instrument { 

...  fields specific to Stock ...

}

Answer 1

您必须设置关系的两边。在Instruments类中，创建用于添加InstrentPrice实体的方法。

public void addInstrumentPrice(ip){
   instrumentPriceList.add(ip);
   ip.setInstrument(this);
}