OneToMany without primary keys

[Chris]

Hi

I'm trying to define a OneToMany / ManyToOne relationship. 

I have the following JPA:

class Definition {

    @Id

    private long id;

    @OneToMany(cascade = CascadeType.ALL, targetEntity = LexicalForm.class, mappedBy = "strongNumber")

    @JoinColumn(name = "raw_strong_number")

    private List<LexicalForm> lexicalForms;

    @Column(unique = true)

    private String strongNumber;

}

And 

class LexicalForm {

    @ManyToOne

    @JoinColumn(name = "raw_strong_number", referencedColumnName = "strong_number")

    private Definition strongNumber;

    private String rawStrongNumber;

}

When I run a query, it produces the wrong join, using the id from Definition and joining it to strongNumber from Lexical form.

select distinct t0.id c0, t0.accented_unicode c1, t0.step_transliteration c2, t0.step_gloss c3 

from definition t0

join lexical_form u1 on u1.raw_strong_number = t0.id  

where (u1.raw_form like ?  or u1.unaccented_form like ? ) 

If I add the strong_number to my Definition class in the join column:     @JoinColumn(name = "raw_strong_number", referencedColumn = "strongNumber"), I get loads of errors spurned out:

Error with the Join on [com.tyndalehouse.step.core.data.entities.lexicon.Definition.lexicalForms]. Could not find the matching foreign key for [id] in table[lexical_form]? Perhaps using a @JoinColumn with the name/referencedColumnName attributes swapped?

Same thing occurs if I swap round the referencedColumn and name columns.

Any ideas? Is this case supported?

Cheers

Chris

[mbell697]

One thing I would consider is the semantics of this structure.  Without a primary key on the LexicalForm table you can't possible store a List of them.  Lists have order.  Without a key there is no way to do that.  If you don't need the Collection to be ordered use a Set in place of a List.

As for the error, look at your database structure, do you have a foreign key setup correctly between these tables?

Cheers,

Mark  

[mbell697]

Additional thoughts: I have no idea if Ebean would allow referencing by non-primary keys or not , but JPA 2 definitely doesn't.  

Also you have something wonky in your mapping:

@OneToMany(cascade = CascadeType.ALL, targetEntity = LexicalForm.class, mappedBy = "strongNumber")

Should be

@OneToMany(cascade = CascadeType.ALL, targetEntity = LexicalForm.class, mappedBy = "rawStrongNumber")

In other words the 'mappedBy' attribute should point to the property in the target class.  That said I don't really know what happens when you define both a 'mappedBy' attribute and a @JoinColumn definition since they are defining the same thing.

It would be vastly easier to just use a primary id key in the LexicalForm entity.

Cheers,

Mark

[Chris]

Thanks for all the comments - I'll try what you've said. The only reason mappedBy is in there twice, is that it's something I've tried, and didn't work. I've tried without and didn't work either. 

Cheers

Chris

[Oliver Kocsis]

I know it is an old post, but try to delete the JoinColumn from the OneToMany relationship side.

Refer: http://stackoverflow.com/questions/11938253/jpa-joincolumn-vs-mappedby