Question

我试图拥有一个链接到多个表的本地化表。我意识到问题在于我使用了本地化ID（例如Localization_Id），因此我无法在没有其他密钥的情况下链接到不同的本地化。我应该以某种方式在数据库中使用连接表或其他顺序ID吗？不确定使用JPA的最佳方法是什么。

提前致谢。

@Entity
public class MyEntityWithLocalization {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    long id;

    @OneToMany(fetch = FetchType.EAGER, cascade={CascadeType.ALL})
    @JoinColumn(name="LOCALIZATION_KEY")
    List<Localization> field1;

    @OneToMany(fetch = FetchType.EAGER, cascade={CascadeType.ALL})
    @JoinColumn(name="LOCALIZATION_KEY")
    List<Localization> field2; //can't be unique from field one as it links to the MyEntityWithLocalization id.

    @OneToMany(fetch = FetchType.EAGER, cascade={CascadeType.ALL})
    @JoinColumn(name="LOCALIZATION_KEY")
    List<Localization> field3; //can't be unique from field one as it links to the MyEntityWithLocalization id.

}

@Entity
public class Localization {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    long id;

    String language;
    String string;

    public Localization(String language, String string) {
        this.language = language;
        this.string = string;
    }

    public Localization(){

    }
}

这会在本地化表中创建一个localization_key，但它只是键入MyEntityWithLocalization的ID - 它需要是另一个唯一值，这使我相信在这种情况下连接表可能有意义。

create table localization (
    id number(19,0) not null,
    language varchar2(255),
    string varchar2(255),
    localization_key number(19,0),
    primary key (id)
);

Answer 1

嗯。为什么不将实体拆分为常量和可本地化的部分？像这样：

@Entity
class MyEntity{
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    long id;

    @OneToMany
    @MapKeyColumn
    Map<String, MyEntityLocalization> localizations;
}

@Embeddable
class MyEntityLocalization {
    String field1;

    String field2;

    String field3;
}

本地化字段在哪里有从语言到本地化的映射？另一种方法是使用特定于Hibernate的注释：

@Entity
class MyEntityWithLocalization {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    long id;

    @OneToMany
    @MapKeyColumn(name="language")
    @WhereJoinTable(clause = "key=1")
    Map<String, String> field1;

    @OneToMany
    @MapKeyColumn(name="language")
    @WhereJoinTable(clause = "key=2")
    Map<String, String> field2;
}


@Entity
public class Localization {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    long id;

    long key;
    String language;
    String string;
}

JPA中从一个表到另一个表的多个单向oneToMany关系列

1 个答案: