在不使用级联的情况下保存双向关联

Question

问题是可以在没有级联注释的情况下将双向关联保存在冬眠中，从而避免瞬态对象异常。

Answer 1

如果您不使用级联，则需要解释两个实体。

entity1.setEntity(entity2)
entity2.setEntity(entity1)
session.save(entity1)
session.save(entity2)

Answer 2

您可以使用 cascade = Cascadetype.all 为此

    @Entity
    @Table(name = "invoice")
    public class Invoice {
        @Id
        @GeneratedValue(strategy = GenerationType.AUTO)
        @Column(name = "id")
        private int id;
        @Column(name = "invoice_date")
        @Temporal(TemporalType.TIMESTAMP)
        private Date invoiceDate;
        @Column(name = "customer")
        private String customer;
        @OneToMany(fetch = FetchType.EAGER, mappedBy = "itemPk.invoice", cascade = CascadeType.ALL)
        private List<InvoiceItem> invoiceItems;
....
}

所以在您的代码中，

InvoiceDao invoiceDao =  new InvoiceDao();
Invoice invoice =  new Invoice();
invoice.setInvoiceDate(new Date());
invoice.setCustomer("Sameera");
InvoiceItem invoiceItem1 =  new InvoiceItem();
invoiceItem1.setQty(10);
invoiceItem1.setPrice(100.10d);
InvoiceItemPK itemPk1 = new InvoiceItemPK();
itemPk1.setInvoice(invoice);
itemPk1.setItem(item);
invoiceItem1.setItemPk(itemPk1);
List<InvoiceItem> items = new ArrayList<>();
items.add(invoiceItem1);
invoice.setInvoiceItems(items);
invoiceDao.save(invoice);