How do I properly cascade save a one-to-one, bidirectional relationship on primary key in Hibernate 3.6

Question

I have an one-to-one, bidirectional entity relationship with shared keys. When I attempt to save the owner of the association I get a "null id generated" exception against the owned side of the relationship. I am utilizing hibernate-entitymanager and using spring for transaction management. Owning Entity ``` @Entity @Table(name = "lead") public class Lead { private Long leadId; private LeadAffiliate leadAffiliate; @Id @GeneratedValue(strategy = GenerationType.AUTO) public Long getLeadId() { return leadId; } @OneToOne(cascade = CascadeType.ALL) @PrimaryKeyJoinColumn public LeadAffiliate getLeadAffiliate() { return leadAffiliate; } } ``` Owned Entity ``` @Entity @Table(name = "lead_affiliate") public class LeadAffiliate { private Long leadId; private Lead lead; @Id public Long getLeadId() { return leadId; } @MapsIdmappedBy = "leadAffiliate") @OneToOne(cascade = CascadeType.All) @PrimaryKeyJoinColumn @JoinColumn(name = "lead_id") public Lead getLead() { return lead; } } ``` and the code…

Accepted Answer

Specification says that derived entity should be the owning side of the relationship:

2.4.1 Primary Keys Corresponding to Derived Identities

The identity of an entity may be derived from the identity of another entity (the "parent" entity) when the former entity (the "dependent" entity) is the owner of a many-to-one or one-to-one relationship to the parent entity and a foreign key maps the relationship from dependent to parent.

In your case `LeadAffiliate ` is derived, so it should be the owner, when `Lead` should be marked as non-owning side by `mappedBy`. The following works in both 3.5.0 and 3.5.6:

```
public class Lead { 
    @Id @GeneratedValue
    private Long leadId; 
 
    @OneToOne(cascade = CascadeType.ALL, mappedBy = "lead")
    private LeadAffiliate leadAffiliate;

...
}
```

.

```
public class LeadAffiliate {  
    @Id
    private Long leadId;  
  
    @OneToOne @MapsId
    private Lead lead;

...
}
```

How do I properly cascade save a one-to-one, bidirectional relationship on primary key in Hibernate 3.6

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