如何在辅助表中的非主键列上连接表？

Question

我有一种情况,我需要在ORM类层次结构中的对象上连接表,其中连接列不是基类的主键.以下是表格设计的示例:

CREATE TABLE APP.FOO
(
    FOO_ID INTEGER NOT NULL,
    TYPE_ID INTEGER NOT NULL,
    PRIMARY KEY( FOO_ID )
)

CREATE TABLE APP.BAR
(
    FOO_ID INTEGER NOT NULL,
    BAR_ID INTEGER NOT NULL,
    PRIMARY KEY( BAR_ID ),
    CONSTRAINT bar_fk FOREIGN KEY( FOO_ID ) REFERENCES APP.FOO( FOO_ID )
)

CREATE TABLE APP.BAR_NAMES
(
    BAR_ID INTEGER NOT NULL,
    BAR_NAME VARCHAR(128) NOT NULL,
    PRIMARY KEY( BAR_ID, BAR_NAME),
    CONSTRAINT bar_names_fk FOREIGN KEY( BAR_ID ) REFERENCES APP.BAR( BAR_ID )
)

这里是映射(为了简洁而消除了吸气剂和固定剂

@Entity
@Table(name = "FOO")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = "TYPE_ID", discriminatorType =    javax.persistence.DiscriminatorType.INTEGER)
public abstract class Foo {
    @Id
    @Column(name = "FOO_ID")
    private Long fooId;
}

@Entity
@DiscriminatorValue("1")
@SecondaryTable(name = "BAR", pkJoinColumns = { @PrimaryKeyJoinColumn(name = "FOO_ID", referencedColumnName = "FOO_ID") })
public class Bar extends Foo{
    @Column(table = "BAR", name = "BAR_ID")
    Long barId;
 }    

如何BAR_NAMES为其连接列不添加映射FOO_ID,但是BAR_ID？

我尝试过以下方法:

@CollectionOfElements(fetch = FetchType.LAZY)
@Column(name = "BAR_NAME")
@JoinTable(name = "BAR_NAMES", joinColumns = @JoinColumn(table = "BAR", name = "BAR_ID", referencedColumnName="BAR_ID"))
List<String> names = new ArrayList<String>();

这会失败,因为用于检索Bar对象的SQL尝试从FOO表中获取BAR_ID值.我也尝试用.替换JoinTable注释

@JoinTable(name = "BAR_NAMES", joinColumns = @JoinColumn(name = "BAR_ID"))

这不会产生SQL错误,但也不会检索任何数据,因为针对BAR_NAMES的查询使用FOO_ID作为连接值而不是BAR_ID.

出于测试目的,我使用以下命令填充了DB

insert into FOO (FOO_ID, TYPE_ID) values (10, 1);
insert into BAR (FOO_ID, BAR_ID) values (10, 20);
insert into BAR_NAMES (BAR_ID, BAR_NAME) values (20, 'HELLO');

许多似乎有效的解决方案在获取ID 10的Foo对象时返回空集合(而不是包含1个名称的集合)

Answer 1

我能够找到解决方案.如果您像这样映射Bar类

@Entity
@DiscriminatorValue("1")
@SecondaryTable(name = "BAR", pkJoinColumns = { @PrimaryKeyJoinColumn(name = "FOO_ID", referencedColumnName = "FOO_ID") })
public class Bar extends Foo {
    @OneToOne
    @JoinColumn(table = "BAR", name = "BAR_ID")
    MiniBar miniBar;
}

并添加以下类

@Entity
@SqlResultSetMapping(name = "compositekey", entities = @EntityResult(entityClass = MiniBar.class, fields = { @FieldResult(name = "miniBar", column = "BAR_ID"), }))
@NamedNativeQuery(name = "compositekey", query = "select BAR_ID from BAR", resultSetMapping = "compositekey")
@Table(name = "BAR")
public class MiniBar {
    @Id
    @Column(name = "BAR_ID")
    Long barId;
} 

然后,您可以将所需的任何类型的映射添加到MiniBar类中,就像barId是主键一样,然后进一步使其在外部Bar类中可用.