与主表不是一对一关系时如何定义SecondaryTable

Question

IN a project, we have to map one Entity to two tables. table part_info stores the commodity info, table part_label stores the label that will be shown on screen.

Table part_info
id part_no part_description

Table part_label
id part_no_label part_description_label

then in our Entity

@Entity
@Table(name="part_info")
@SecondaryTable(name="part_label",pkJoinColumns=    {@PrimaryKeyJoinColumn(name="id",referencedColumnName="id")})
public class PartInfo implements Serializable {
    @id
    private int id;
@Column(name = "part_no")
private String partNo;
@Column(name = "part_description")
private String partDesc;
@Column(table="part_label",name="part_no_label")
private String partNoLabel;
@Column(table="part_label",name="part_description_label")
private String partDescLabel;
    ....
}

but this will only map one record of part_info to one record of part_label.

In our case, different part info may use the same part label. eg we will use label retrieved from part_label as below:

Part# 
Part Desc

but we retrieved many part info from part_info table

PA123 AAA
PA123 DDD
PA234 BBB
PA345 CCC

Then in UI, we will show as:

Part#:PA123  Part Desc:AAA
Part#:PA123  Part Desc:DDD

If use above @SecondaryTabel, each part_info and each part_label are One-To-One relationship, if need to retrieve two records of parts PA123, also need to retrieve same label twice.

Is there any way that one part label can map to many part info?

Answer 1

You misunderstand SecondaryTable, since it is only ever for one to one situation, and if the object is deleted then the row from both tables is deleted. There is no "reuse" of entries in the secondary table ... since the secondary table has a FK to the primary table!!!

If you want to reuse some data then make that a separate entity.

Answer 2

我认为最合理的解决办法是模拟PartLabel作为一个独立的实体，并创建一个ManyToOne的关系PartInfo到PartLabel 。