Question

我正在使用一个完全没有规范化的遗留数据库。他们一直在程序中编写关系（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，但我需要映射表之间的OneToMany关系。

例如，我有一个表Invoice和一个表Item。

表发票包含这些键。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

表项目包含这些键，前三个键的类型和值与相应的发票键相同。

item_serial_id,
item_number_id,
item_date,
item_otherkey1

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

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

我也尝试过了here步骤，并在Invoice上创建了一个@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

如何使用此数据库创建关系？或者我应该放弃并手动选择项目？

Answer 1

由于时间限制，我无法等待正确答案。

我最终在示例中创建了一个连接这些表的视图，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中映射了视图。这对我有用。

Answer 2

我认为你需要这样做。

您的发票表有一个主键和相应的@ID属性。
发票表中的嵌入式ID应仅包含Item表中的3个字段。
创建一个ItemID表，用于映射这三个字段，并在Invoice表中引用它。

它看起来像这样......

@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，并为ItemId类重写hashCode（）和equals（Object o）。

在您的发票中，请参阅此ItemId（就像您使用embeddedId和属性覆盖一样。

目前，您在外键定义中嵌入了5个字段，但在itemID类中只有3个字段。您不需要连接表，只需创建复合键类（包含3个字段）并将其嵌入发票表中。

Hibernate OneToMany使用遗留数据库的注释

2 个答案: