子主键未由hibernate更新

Question

我使用hibernate和spring数据来保存数据库中的实体。我将子元素附加到父元素，反之亦然。一切都在数据库中正确保存，以及子实例。

再次调用save方法后，子元素将被保存两次。我发现，原因是，该框架在持续存在后不会更新子项ID。它始终为零。父ID已正确更新。

知道如何解决这个问题吗？

Receipt.java：

@Entity    
@javax.persistence.Table(name = "receipts")
public class Receipt {

    private int id;
    /*
    *  [...]
    */

    @Id
    @Column(name = "id")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    @OneToMany(fetch = FetchType.EAGER,cascade = CascadeType.ALL)
    @JoinColumn(name = "receipt_id",referencedColumnName = "id")
    private List<ReceiptItem> getReceiptItemList() {
        return receiptItemList;
    }

    private void setReceiptItemList(List<ReceiptItem> receiptItemList) {
        this.receiptItemList = receiptItemList;
    }

    /*
    *  [...]
    */
}

ReceiptItem.java：

@Entity
@Table(name = "receipt_items")
public class ReceiptItem {

    private int id;
    /*
    *  [...]
    */

    @Id
    @Column(name = "id")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "receipt_id")

    public Receipt getReceipt() {
        return receipt;
    }

    public void setReceipt(Receipt receipt) {
        this.receipt = receipt;
    }
}

存储

item = new ReceiptItem();
item.setReceipt(receipt);

receipt.getReceiptItemList().add(item);

// this should create the new ReceiptItem instance
receiptService.save(receipt);
System.out.println("ItemId: "+item.getId()); //but the id is still 0

// calling save method twice results in a second entry in the database
// instead of updating the previously inserted one
receiptService.save(receipt);
System.out.println("ItemId: "+item.getId()); 

输出：

ItemId: 0 
ItemId: 0