如何在Springboot jpa中保存onetomany中的children数据列表

Question

父数据正在保存，但子数据列表未保存在表中。 来自邮递员的数据

{"billno":"nur-1001", "grandTotal": 5000,"billcart":[{"itemcode":"SU10027", "soldPrice":0},{"itemcode":"SU10027","soldPrice":1100}]}

Bill 是父实体 & billcart 是子实体

@NoArgsConstructor @AllArgsConstructor @Data @Entity
public class Bill { 
    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private Long id;
    private String billno;  
    private Long grandTotal;

    @OneToMany(mappedBy = "bill", cascade = CascadeType.ALL)
    @JsonIgnore
    private List<Billcart> billcart = new ArrayList<>();

    public Bill( String billno, Long grandTotal, List<Billcart> billcart) {
        this.billno = billno;       
        this.grandTotal = grandTotal;
        this.billcart = billcart;
        this.billcart.forEach(e -> e.setBill(this));
    }
}

子实体

@NoArgsConstructor @AllArgsConstructor @Data @Entity
public class Billcart {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String itemcode;
    private Integer soldPrice;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "bill_id")
    private Bill bill;

控制器

public void saveBill(@RequestBody Bill request) { 
List<Billcart> billscart = request.getBillcart().stream()
                .map(e -> new Billcart(e))
                .collect(Collectors.toList());

        Bill bill = new Bill(request.getBillno(), request.getGrandTotal() , billscart);
        billRepository.save(bill);