在Hibernate的父类中保存历史表中的最后一条记录

Question

线程标题可能有点误导，但我的问题是:

我有这三个表，使用Hibernate(带注释)映射:

@SuppressWarnings("serial")
@Entity
@Table(name = "payment", catalog = "db")
public class Payment implements java.io.Serializable {
    private Long paymentId;
    private Set<PaymentStateHistory> paymentStateHistory = new HashSet<>(0);
    @Id
    @Column(name = "payment_id", unique = true, nullable = false)
    public long getPaymentId() {
        return this.idSolicitud;
    }
    public void setPaymentId(Long paymentId) {
        this.paymentId = paymentId;
    }
    @OneToMany(fetch = FetchType.LAZY, mappedBy = "payment")
    public Set<PaymentStateHistory> getPaymentStateHistory() {
        return this.paymentStateHistory;
    }
    public void setPaymentStateHistory(Set<PaymentStateHistory> paymentStateHistory) {
        this.paymentStateHistory = paymentStateHistory;
    }
}

---

@SuppressWarnings("serial")
@Entity
@Table(name = "payment_state_history", catalog = "db")
public class PaymentStateHistory implements java.io.Serializable {
    private Long stateHistoryId;
    private PaymentState paymentState;
    private Payment payment;
    private Date stateDate;
    @Id
    @GeneratedValue(strategy = IDENTITY)
    @Column(name = "state_history_id", unique = true, nullable = false)
    public Long getStateHistoryId() {
       return this.stateHistoryId;
    }
    public void setStateHistoryId(Long stateHistoryId) {
       this.stateHistoryId = stateHistoryId;
    }
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "state_id", nullable = false)
    public PaymentState getPaymentState() {
       return this.paymentState;
    }
    public void setPaymentState(PaymentState paymentState) {
       this.paymentState = paymentState;
    }
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "payment_id", nullable = false)
    public Payment getPayment() {
       return this.payment;
    }
    public void setPayment(Payment payment) {
       this.payment = payment;
    }
    @Temporal(TemporalType.TIMESTAMP)
    @Column(name = "state_date", length = 19)
    public Date getStateDate() {
       return this.stateDate;
    }
    public void setStateDate(Date stateDate) {
       this.stateDate = stateDate;
    }
}

---

@SuppressWarnings("serial")
@Entity
@Table(name = "payment_state", catalog = "db")
public class PaymentState implements java.io.Serializable {
    private Integer paymentStateId;
    private String info;
    private Set<PaymentStateHistory> paymentStateHistory = new HashSet<>(0);
    @Id
    @GeneratedValue(strategy = IDENTITY)
    @Column(name = "payment_state_id", unique = true, nullable = false)
    public Integer getPaymentStateId() {
        return this.paymentStateId;
    }
    public void setPaymentStateId(Integer paymentStateId) {
        this.paymentStateId = paymentStateId;
    }
    @Column(name = "info", nullable = false, length = 100)
    public String getInfo() {
        return this.info;
    }
    public void setInfo(String info) {
        this.info = info;
    }
    @OneToMany(fetch = FetchType.LAZY, mappedBy = "paymentState")
    public Set<PaymentStateHistory> getPaymentStateHistory() {
        return this.paymentStateHistory;
    }
    public void setPaymentStateHistory(Set<PaymentStateHistory> paymentStateHistory) {
        this.paymentStateHistory = paymentStateHistory;
    }
}

基本上，payment_state_history维护了支付状态更改的历史记录，每个记录都有状态更改的日期。

这种映射方式工作得很好，Payment包含了一组它所有的状态变化，但是我想知道是否有一种方法可以映射这些关系，我可以在Payment中保存最后(最新日期)PaymentState，所以我可以通过加载所需的Payment来访问它，并做一些类似payment.getLastState()的事情。

支付表还有一个"lastrongtate_id"列，将该行与payment_state_history表中该支付的最后状态关联起来(每次安全更改时都会更新)。我知道我可以映射那个id，并使用那个id找到相应的状态，但它需要对数据库进行更多的查询，使系统变慢，所以在Payment上保存一个PaymentState对象将是理想的。

Answer 1

您可以在付款实体中添加如下新成员

private PaymentStateHistory lastPaymentStateHistory;

如下所示添加getter和setter

public void setLastPaymentStateHistory(){
       //code to loop throught paymentStateHistory and set the lastPaymentStateHistory
}
@Transient
public void getLastPaymentStateHistory(){ 
   return this.lastPaymentHistory;
}

然后更新paymentStateHistory的setter，如下所示

    public void setPaymentStateHistory(Set<PaymentStateHistory> paymentStateHistory) {
    this.paymentStateHistory = paymentStateHistory;
    setLastPaymentStateHistory();
}