Hibernate API中的ElementCollection createAlias [英] ElementCollection createAlias in hibernate API

问题描述

没有人知道是否以及如何解决以下问题（写在JPA API中）可以使用hibernate标准API编写吗？ 更具体地说，我有一个讨论实体包含参与者列表（这是一个用户名列表）：

  @ElementCollection 
 @Column（name = user_name）
 @CollectionTable（name =DISCUSSION_USER，joinColumns = @JoinColumn（name =DISCUSSION_ID））
 @OrderColumn（name =ORDER_INDEX）
 private List< String> ;参与者=新的ArrayList< String>（）; 
  

现在我需要检索给定用户名是参与者的所有讨论。

如果我为Participant创建了一个实体，这将很简单：

  Criteria crit = 。的getSession（）个createCriteria（Discussion.class）; 
 crit.createAlias（参与者，p）; 
 crit.add（Restrictions.eq（p.userName，portalUsername））; 
  

但我无法用非实体创建别名...

解决方案

正如这里我想要的是不可能的：

使用ElementCollection代替OneToMany的限制是目标对象不能被查询，坚持，独立于其父对象合并。它们是严格私有的（依赖）对象，与嵌入式映射相同。在ElementCollection上没有级联选项，目标对象总是被持久化，合并，并与父级一起被移除。

所以，我用一个OneToMany来代替。

does anyone know if and how the solution for following question (which is written in the JPA API) can be written using the hibernate criteria API?

To be more specific I have a Discussion entity that contains a list of participants (which is a list of usernames):

@ElementCollection
@Column(name = "user_name")
@CollectionTable(name = "DISCUSSION_USER", joinColumns = @JoinColumn(name = "DISCUSSION_ID"))
@OrderColumn(name = "ORDER_INDEX")
private List<String> participants = new ArrayList<String>();

Now I need to retrieve all Discussions where a given username is a participant.

If I would have created an entity for Participant this would be straightforward:

    Criteria crit = getSession().createCriteria(Discussion.class);
    crit.createAlias("participants", "p");
    crit.add(Restrictions.eq("p.userName", portalUsername));

But I can't create an alias with a non entity...

解决方案

As explained here what I wanted is not possible:

The limitations of using an ElementCollection instead of a OneToMany is that the target objects cannot be queried, persisted, merged independently of their parent object. They are strictly privately-owned (dependent) objects, the same as an Embedded mapping. There is no cascade option on an ElementCollection, the target objects are always persisted, merged, removed with their parent.

So, I used a OneToMany instead.

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