如何在JPA中拥有相同类型的2个集合？ [英] How to have 2 collections of the same type in JPA?

问题描述

我在JPA中有2个实体：条目和注释。 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>（）; 
 
 ... 
} 
  

JPA + Hibernate创建Entry表，注释表和SINGLEEntry_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，主键（Entry_id，dnr），unique（descriptionComments_id），unique（postMortemComments_id））

存储对象失败，因为 descriptionComments_id 和 postMortemComments_id 不能为not null

如何使用JPA + Hibernate存储包含两个相同类型集合的对象？

解决方案

这是许多Hibernate的bug之一（ HHH-3410 ）。

我已经设法通过添加 @JoinTable 注释到 @OneToMany 关系，每个都有自己的表名。

在您的情况下，它将如下所示：

  @OneToMany （fetch = FetchType.EAGER，cascade = CascadeType.ALL）
 @JoinTable（name =entity_descriptioncomments）
 @IndexColumn（base = 1，name =dnr）
 private List<评论> 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：必须添加 @IndexColumn  
  


$ b 注释（因为有多个EAGER包的其他Hibernate问题： HHH -1718 / EJB-346 ）。

I've got 2 entities in JPA: Entry and Comment. Entry contains two collections of Comment objects.

@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>();

    ...
}

To store such objects, JPA+Hibernate creates "Entry" table, "Comment" table and 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))

Storing of objects fail as descriptionComments_id and postMortemComments_id cannot be "not null" at the same time.

How do I store object containing two collections of the same type using JPA+Hibernate?

解决方案

This is one of the many Hibernate bugs (HHH-3410 to be precise).

I've managed to fix it by adding @JoinTable annotations to @OneToMany relationships, each having its own table name.

In your case it would look like this:

@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>();

Note: you must add @IndexColumn annotation as well (because of the other Hibernate issue with multiple EAGER bags: HHH-1718/EJB-346).

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