springboot中如何映射实体类对象？

Question

这是我的实体类，我用它来保存客户的详细信息以及购买的详细信息和购买的产品以及付款模块，它很好地保存在数据库中，但检索结果为 null。

@Entity
@Table(name = "productpurchasedata")
public class Test {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int customerid;
    @ManyToOne(cascade = { CascadeType.ALL })
    @JoinColumn(name = "customerid", insertable = false, updatable = false)
    private CustomerProductSave customerProductSave;
    @ManyToOne(cascade = { CascadeType.ALL })
    @JoinColumn(name = "customerid", insertable = false, updatable = false)
    private PurchaseDetails purchasedetails;
    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    @JoinColumn(name = "customerid")
    private List<ProductPurchased> productpurchased;
    @ManyToOne(cascade = { CascadeType.ALL })
    @JoinColumn(name = "customerid", insertable = false, updatable = false)
    private PaymentHistory paymenthistory;

在这里，我可以保存导致如下结果的数据：-

{
    "customerid": 1,
    "customerProductSave": {
        "customerids": 2,
        "name": "nitesh",
        "mailid": "niteshbhushan95@gmail.com",
        "address": "hyd",
        "city": "telanagana",
        "state": "telanagana",
        "postalcode": "847226",
        "mobileno": 6300769631
    },
    "purchasedetails": {
        "purchasedate": "22-07-2021",
        "modeofpayment": "paytm",
        "emiapplicable": false,
        "totalamount": 21000,
        "purchaseId": 4
    },
    "productpurchased": [
        {
            "purchaseid": 5,
            "purchaseamount": 2000,
            "purchasedproductid": 1,
            "productquantity": 0
        },
        {
            "purchaseid": 6,
            "purchaseamount": 2000,
            "purchasedproductid": 1,
            "productquantity": 0
        }
    ],
    "paymenthistory": {
        "transactionid": 3,
        "paymentstatus": "paid"
    }
}

现在，当我尝试通过 customerid 检索数据时，它不接受，它将消息显示为 null ，我不太可能在映射中出现一些错误

Answer 1

尝试使用 fetch = FetchType.EAGER 而不是 fetch = FetchType.LAZY 在所有映射购买细节和产品购买和支付模块