如何在JPA中拥有2个相同类型的集合？

Question

我在JPA中有两个实体:Entry和Comment.Entry包含两个Comment对象集合.

@Entity
public class Entry {
    ...

    @OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    @IndexColumn(base = 1, name = "dnr")
    private List<Comment> descriptionComments = new ArrayList<Comment>();

    @OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    @IndexColumn(base = 1, name = "pmnr")
    private List<Comment> postMortemComments = new ArrayList<Comment>();

    ...
}

为了存储这样的对象,JPA + Hibernate创建了"Entry"表,"Comment"表和SINGLE"Entry_Comment":

create table Entry_Comment (Entry_id integer not null, postMortemComments_id integer not null, pmnr integer not null, descriptionComments_id integer not null, dnr integer not null, primary key (Entry_id, dnr), unique (descriptionComments_id), unique (postMortemComments_id))

对象的存储失败,descriptionComments_id并且postMortemComments_id不能同时"不为空".

如何使用JPA + Hibernate存储包含两个相同类型集合的对象？

Answer 1

这是许多Hibernate错误之一(准确地说是HHH-3410).

我已经设法通过向关系添加@JoinTable注释来修复它@OneToMany,每个关系都有自己的表名.

在你的情况下,它看起来像这样:

@OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
@JoinTable(name="entity_descriptioncomments")
@IndexColumn(base = 1, name = "dnr")
private List<Comment> descriptionComments = new ArrayList<Comment>();

@OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
@JoinTable(name="entity_postmortemcomments")
@IndexColumn(base = 1, name = "pmnr")
private List<Comment> postMortemComments = new ArrayList<Comment>();

注意:您还必须添加@IndexColumn注释(因为多个EAGER包的其他Hibernate问题:HHH-1718/EJB-346).