Hibernate OneToMany 使用遗留数据库的注释

Question

我正在使用一个根本没有标准化的遗留数据库。他们直接在程序中编码关系（用 Uniface 编写）。现在，他们正在迁移到 Java。遗憾的是，我无法更改数据库，但我需要在表之间映射 OneToMany 关系。

例如，我有一个表 Invoice 和一个表 Item。

表 Invoice 具有这些键。其中前三个用作与 Item 的关系的外键：

invoice_serial_id,  
invoice_number_id,  
invoice_date,
invoice_otherkey1,
invoice_otherkey2  

表 Item 有这些键，前三个与相应的 Invoice 键具有相同的类型和值。

item_serial_id,
item_number_id,
item_date,
item_otherkey1

我使用 hibernate 的逆向工程创建了表，生成了 Invoice.java、InvoiceId.java、Item.java 和 ItemId.java，然后手动创建了 @OneToMany 和 @ManyToOne 注释。这是到目前为止的代码：

Invoice.java

@Entity
@Table(name = "INVOICE")
public class Invoice implements java.io.Serializable {

    private static final long serialVersionUID = -2073462863929322522L;

    @EmbeddedId
        @AttributeOverrides( {
            @AttributeOverride(name = "invoiceSerialId", column = @Column(name = "INVOICE_SERIAL_ID", nullable = false, length = 9)),
            @AttributeOverride(name = "invoiceNumberId", column = @Column(name = "INVOICE_NUMBER_ID", nullable = false, length = 9)),
            @AttributeOverride(name = "invoiceDate", column = @Column(name = "INVOICE_DATE", nullable = false, length = 7)),
            @AttributeOverride(name = "invoiceOtherkey1", column = @Column(name = "INVOICE_OTHERKEY1", nullable = false, length = 7)),
            @AttributeOverride(name = "invoiceOtherkey2", column = @Column(name = "INVOICE_OTHERKEY2", nullable = false, length = 7))
    })
    private InvoiceId id;

    @OneToMany(mappedBy = "invoice")
    private Set<Item> items;
}

Item.java

@Entity
@Table(name = "ITEM")
public class Item implements java.io.Serializable {
    private static final long serialVersionUID = -2840038244580784867L;

    @EmbeddedId
        @AttributeOverrides( {
            @AttributeOverride(name = "itemSerialId", column = @Column(name = "ITEM_SERIAL_ID", nullable = false, length = 9)),
            @AttributeOverride(name = "itemNumberId", column = @Column(name = "ITEM_NUMBER_ID", nullable = false, length = 9)),
            @AttributeOverride(name = "itemDate", column = @Column(name = "ITEM_DATE", nullable = false, length = 7)),
            @AttributeOverride(name = "itemOtherkey1", column = @Column(name = "ITEM_OTHERKEY1", nullable = false, length = 7))
    })
    private ItemId id;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumns({
        @JoinColumn(name = "ITEM_SERIAL_ID", referencedColumnName = "INVOICE_SERIAL_ID"),
        @JoinColumn(name = "ITEM_NUMBER_ID", referencedColumnName = "INVOICE_NUMBER_ID"),
        @JoinColumn(name = "ITEM_DATE", referencedColumnName = "INVOICE_DATE")
    })
    private Invoice invoice;
}

我收到以下错误：

org.hibernate.AnnotationException: referencedColumnNames(INVOICE_SERIAL_ID, INVOICE_NUMBER_ID, INVOICE_DATE) of com.just.an.stupid.example.app.Item.invoice referencing com.just.an.stupid.example.app.Invoice not mapped to a single property

我也尝试按照步骤此处，并在发票上创建一个@joinTable，例如

@JoinTable(name = "INVOICE_ITEM",
    joinColumns = {
        @JoinColumn(name = "ITEM_SERIAL_ID", referencedColumnName = "INVOICE_SERIAL_ID"),
        @JoinColumn(name = "ITEM_NUMBER_ID", referencedColumnName = "INVOICE_NUMBER_ID"),
        @JoinColumn(name = "ITEM_DATE", referencedColumnName = "INVOICE_DATE")
    },
    inverseJoinColumns = {
        @JoinColumn(name = "INVOICE_SERIAL_ID", referencedColumnName = "ITEM_SERIAL_ID"),
        @JoinColumn(name = "INVOICE_NUMBER_ID", referencedColumnName = "ITEM_NUMBER_ID"),
        @JoinColumn(name = "INVOICE_DATE", referencedColumnName = "ITEM_DATE")
    }
)

但我得到了这个：

org.hibernate.AnnotationException: A Foreign key refering com.just.an.stupid.example.app.Invoice from com.just.an.stupid.example.app.Item has the wrong number of column. should be 5

如何创建一个使用这个数据库的关系？或者我应该放弃并手动选择项目？

Answer 1

由于时间有限，我没能等到正确的答案。

我最终创建了一个连接示例中这些表的视图，如下所示：

create or replace table invoice_items as
select distinct
  i.field_1,
  i.field_2,
  i.field_3,
  it.field_4
from
  invoice i
inner join
  item it
on
  (i.invoice_serial_id = it.item_serial_id and
   i.invoice_number_id = it.item_number_id and
   i.invoice_date = it.item_date
  )

然后我在 Hibernate 中映射了该视图。这对我有用。

Answer 2

我认为你需要这样做。

1. 您的发票表有一个带有相应@ID 属性的主键。

2. 发票表中的嵌入 ID 应仅包含项目表中存在的 3 个字段。

3. 创建一个 ItemID 表，映射这三个字段，并在 Invoice 表中引用它。

它会看起来像这样

@Embeddable
public class ItemId implements java.io.Serializable {

private Long serialNo;
private Long itemNumber;
    private Date itemDate

..............
使用相应的 setter 和 getter，并覆盖 ItemId 类的 hashCode() 和 equals(Object o) 。

1. 在您的发票中引用此 ItemId（就像您使用嵌入 ID 和属性覆盖所做的那样。

目前，您在外键定义中嵌入了 5 个字段，但在 itemID 类中仅强调 3 个字段。您不需要联接表中，您只需创建一个复合键类（包含 3 个字段）并将其嵌入到发票表中。