使用 JpaRepository 更新实体中的列表项（保留主键）

Question

最好用一个例子来问……

实体PurchaseOrder 有一个PurchaseOrderDetail 列表。 OneToMany 关系。 Entity 和 list items 不能直接保存使用的 JPA 方法，因为涉及一些计算。 当我们对PurchaseOrder 执行更新时，我们必须保留主键，这样我们才能像这样更新

PurchaseOrder purchaseOrder = purchaseOrderRepository.getOne(purchaseOrderRequest.getId());
purchaseOrder.setSupplier(purchaseOrderRequest.getSupplier());
purchaseOrder.setDollarRate(purchaseOrderRequest.getDollarRate());
purchaseOrder.setShippingCost(purchaseOrderRequest.getShippingCost());
return purchaseOrderRepository.save(purchaseOrder);

但是如何Beautifully更新List<PurchaseOrderDetail> purchaseOrderDetails？

我有以下代码，它将删除现有的列表项并插入丢失主键的新项。但是JPA way 是做什么的，以便在更新期间发生以下情况

1. If some items were deleted they should be deleted from DB.
2. If some items were updated they should be updated preserving the primary keys.
3. If some new items are added they should be created having new primary keys.

代码

purchaseOrder.setPurchaseOrderDetails(null);

        for (PurchaseOrderDetailRequest purchaseOrderDetailRequest : purchaseOrderRequest.getPurchaseOrderDetails())
        {
            PurchaseOrderDetail purchaseOrderDetail = new PurchaseOrderDetail();
            purchaseOrderDetail.setPartNumber(purchaseOrderDetailRequest.getPartNumber());
            purchaseOrderDetail.setDescription(purchaseOrderDetailRequest.getDescription());
            purchaseOrderDetail.setQuantity(purchaseOrderDetailRequest.getQuantity());
            purchaseOrderDetail.setUnitPriceInDollars(purchaseOrderDetailRequest.getUnitPriceInDollars());
            purchaseOrderDetail.setTotalPriceInDollars(purchaseOrderDetailRequest.getQuantity() * purchaseOrderDetailRequest.getUnitPriceInDollars());
            purchaseOrderDetail.setUnitPriceInSAR(purchaseOrder.getDollarRate() * purchaseOrderDetailRequest.getUnitPriceInDollars());
            purchaseOrderDetail.setTotalPriceInSAR(purchaseOrderDetailRequest.getQuantity() * purchaseOrderDetail.getUnitPriceInSAR());
            purchaseOrderDetail.setUnitCost(purchaseOrderDetail.getUnitPriceInSAR() + shippingFactor);
            purchaseOrder.addPurchaseOrderDetail(purchaseOrderDetail);
        }

采购订单

@Entity
@Table(name = "purchaseOrders")
public class PurchaseOrder extends UserDateAudit
{
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @NotBlank
    @Size(max = 140)
    private String supplier;

    @NotNull
    private Float dollarRate;

    @NotNull
    private Float amount;

    @NotNull
    private Float shippingCost;

    @OneToMany(
            mappedBy = "purchaseOrder",
            cascade = CascadeType.ALL,
            fetch = FetchType.EAGER,
            orphanRemoval = true
    )
    @Fetch(FetchMode.SELECT)
    @BatchSize(size = 150)
    private List<PurchaseOrderDetail> purchaseOrderDetails = new ArrayList<>();
}

PurchaseOrderDetail

@Entity
@Table(name = "purchaseOrderDetails")
public class PurchaseOrderDetail
{
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @NotBlank
    @Size(max = 50)
    private String partNumber;

    @Size(max = 256)
    private String description;

    @NotNull
    private Integer quantity;

    @NotNull
    private Float unitPriceInDollars;

    @NotNull
    private Float totalPriceInDollars;

    @NotNull
    private Float unitPriceInSAR;

    @NotNull
    private Float totalPriceInSAR;

    @NotNull
    private  Float unitCost;

    @ManyToOne(fetch = FetchType.LAZY, optional = false)
    @JoinColumn(name = "purchaseOrder_id", nullable = false)
    private PurchaseOrder purchaseOrder;
}

Answer 1

JpaRepository.save() 根据实体状态执行em.persist() 或em.merge()。
而且您还配置了@OneToMany 与cascade = CascadeType.ALL 和orphanRemoval = true 关系的映射，所以您的方法是正确的。
您必须在代码中更新 PurchaseOrder 中定义的 List 的 PurchaseOrderDetail 元素，而不是为它们创建新实例。
如果需要，您可以在 Map 中添加现有元素以加快查找处理。

// collect existing details into a map to fast up
Map<Long, PurchaseOrderDetail> purchaseOrderDetailByIdMap = 
purchaseOrder.getPurchaseOrderDetails()
             .stream()
             .collect(toMap(PurchaseOrderDetail::getId, p -> p);

//collect new details into a list
List<PurchaseOrderDetail> updatedDetails = 
purchaseOrderRequest.getPurchaseOrderDetails()
                    .stream()
                    .map(detailReq -> mapDetailRequestToDetail(detailReq, 
                                      purchaseOrderDetailByIdMap))
                    .collect(toList());

// overwrite the relationship with the updatedDetails var
purchaseOrder.setPurchaseOrderDetails(updatedDetails);

// ...      

// mapping function extracted to be clearer
private PurchaseOrderDetail mapDetailRequestToDetail(PurchaseOrderDetailRequest purchaseOrderDetailRequest, 
                         Map<Long, PurchaseOrderDetail> purchaseOrderDetailByIdMap) {             

    // Here you get the existing element with the defined id or you create a new one            
    PurchaseOrderDetail purchaseOrderDetail = 
    purchaseOrderDetailByIdMap.computeIfAbsent(purchaseOrderDetailRequest.getId(), k-> new PurchaseOrderDetail());

    // set fields
    purchaseOrderDetail.setPartNumber(purchaseOrderDetailRequest.getPartNumber());
    purchaseOrderDetail.setDescription(purchaseOrderDetailRequest.getDescription());
    purchaseOrderDetail.setQuantity(purchaseOrderDetailRequest.getQuantity());
    purchaseOrderDetail.setUnitPriceInDollars(purchaseOrderDetailRequest.getUnitPriceInDollars());
    purchaseOrderDetail.setTotalPriceInDollars(purchaseOrderDetailRequest.getQuantity() * purchaseOrderDetailRequest.getUnitPriceInDollars());
    purchaseOrderDetail.setUnitPriceInSAR(purchaseOrder.getDollarRate() * purchaseOrderDetailRequest.getUnitPriceInDollars());
    purchaseOrderDetail.setTotalPriceInSAR(purchaseOrderDetailRequest.getQuantity() * purchaseOrderDetail.getUnitPriceInSAR());
    purchaseOrderDetail.setUnitCost(purchaseOrderDetail.getUnitPriceInSAR() + shippingFactor);

    return purchaseOrderDetail;         
}