JPA注释 - 如何从与当前对象不同的表中检索单个值？

Question

如何将单个值从另一个表中的列映射到当前对象？

例:

class Foo {
    @Id
    @Column(name="FOO_ID")
    private String fooId;

    @Column(name="FOO_A")
    private String fooA;

    //Column to map to another table?
    //is a one to one mapping - but don't want a separate object for this.
    private String barCode;
}

表: Fields

富: FOO_ID, FOO_A

酒吧: FOO_ID, BAR_CODE

如何在BAR_CODE不创建单独对象(或辅助表)的情况下检索字段JPA annotations？

Answer 1

使用辅助表.这允许您一对一地映射实体,另一个表并定义使用它的列映射.

例:

@Entity
@Table(name = "foo")
@SecondaryTable(name = "other_table", pkJoinColumns=@PrimaryKeyJoinColumn(name="id", referencedColumnName="FOO_ID"))
public class Foo {
    @Id
    @Column(name="FOO_ID")
    private String fooId;

    @Column(name="FOO_A")
    private String fooA;

    @Column(table="OtherTable", name="barCode")
    private String barCode;
}