JPA / Hibernate OneToOne与相同PK的双向关系错误的插入顺序

Question

I'm trying to set up a OneToOne relationship between two entities that share the same PK:

+----------------------------------+   +----------------+-----------------+        
|              Item                |   |              Stats               |
+----------------+-----------------+   +----------------+-----------------+
| reference (PK) |  other data...  |   | reference (PK) |  other data...  |
+----------------+-----------------+   +----------------+-----------------+
|          ABCD  |      ...        |   |          ABCD  |      ...        |
|           XYZ  |      ...        |   |           XYZ  |      ...        |
+----------------+-----------------+   +----------------+-----------------+

where Stats.reference is a FK to Item.reference :

alter table Stats 
    add constraint FK_8du3dv2q88ptdvthk8gmsipsk 
    foreign key (reference) 
    references Item;

This structure is generated from the following annotaded classes:

@Entity
public class Item {
   @Id
   private String reference;

   @OneToOne(mappedBy = "item", optional = false)
   @Cascade({CascadeType.SAVE_UPDATE})
   @Fetch(FetchMode.SELECT)
   private Stats stats;

   // ...
}

@Entity
public class Stats {

   @Id
   @OneToOne
   @JoinColumn(name = "reference")
   @Fetch(FetchMode.SELECT)   
   private Item item;  

   // ...
}

A new Item is creted as follows:

Item item = new Item();
item.setReference("ABC");
Stats stats = new Stats();
stats.setItem(item);
item.setStats(stats);
session.save(item);

My problem is when I do session.save(item) the INSERT statements order are wrong. Hibernate first tries to insert into Stats table instead of Item , resulting in a FK constraint error.

How can I solve this issue? Thanks in advance.

Answer 1

Since your class Stats owns the association, try to do :

stats.setItem(item);
session.save(stats)

Answer 2

since you have one to one relationship between item and state and item has stats key as FK, and here you entity object should look like this

Item{

@OneToOne
@JoinColumn(name = "stat_id", nullable=false) //incase if you allow null
private stats stats

}

in stats entity no need to add relation annotation, since we defined in Item

while saving , you just save item entity, stats also get inserted

item.setStats(stats);
session.save(item);

in case if you want to save stats separately and items separately,

then you have define cascade type as DETACH for stats

 Class Item{

    @OneToOne(cascade=CascadeType.DETACH)
    @JoinColumn(name = "stat_id", nullable=false) //incase if you allow null
    private stats stats
}

Answer 3

The @JoinColumn annotation in Stats entity isn't complete, the attribute referencedColumnName must be specified.

public abstract java.lang.String referencedColumnName

(Optional) The name of the column referenced by this foreign key column.

@Entity
public class Stats {

   @Id
   @OneToOne
   @JoinColumn(name = "reference", referencedColumnName = "reference")
   @Fetch(FetchMode.SELECT)   
   private Item item;  

   // ...
}