Home » Modeling » EMF » Re: modelling associations
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| Re: modelling associations [message #427601 is a reply to message #427600] |
Tue, 24 February 2009 05:17   |
 Martin Taal
Messages: 5468
Registered: July 2009 |
Senior Member |
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Hi RJ,
As a default Teneo will use join tables for non-containment relations. You can disable this by setting this persistence
option to false:
PersistenceOptions.JOIN_TABLE_FOR_NON_CONTAINED_ASSOCIATIONS
When this option is false then you can set a join table for a an association by setting the @JoinTable annotation.
As you are new to EMF, a containment relation is a parent-child relation whereby the child depends on the parent for its
existence. In the library example, a writer and book are contained in a library. The writer and book relationship in
this model is non-containment.
The reason that Teneo (as a default) uses join tables for non-containment relations is that this is safer (less change
on name clashes) when having very complex models with multiple inheritance.
gr. Martin
RJDAG wrote:
> Thank you for the quick response.
>
> I found the cascadenotall example on the elver website:
> http://www.elver.org/hibernate/ejb3_examples.html
>
> I wish to generate an hbm like
> CascadeNotallAction_mysql_a_o_hibernate.hbm.xml but when i generate it
> I get hibernate.hbm.xml.
>
> I do not want to use the write_books table to store theWriter to books
> relationship.
>
> Thanks
> RJ
>
> "Martin Taal" <mtaal@elver.org> wrote in message
> news:gnv6a3$7ld$1@build.eclipse.org...
>> Hi RJ,
>> There is no more detailed article available then what is available on
>> elver.org or the hibernate manual (or posts on the
>> newsgroup).
>>
>> In this case there is a many-to-many present in the mapping, but it has
>> the special attribute unique="true", which means
>> it is in fact a one-to-many. A OneToMany annotation can still be mapped
>> with a many-to-many in hbm (as long as it has
>> unique="true"). See these parts of the hibernate manual:
>> http://www.hibernate.org/hib_docs/reference/en/html/assoc-un idirectional-join.html
>> http://www.hibernate.org/hib_docs/reference/en/html/assoc-bi directional-join.html
>>
>> Note that support for Teneo is given on the EMF newsgroup which I cc-ed.
>>
>> gr. Martin
>>
>> RJDAG wrote:
>>> Hello
>>>
>>> I am new to Teneo and Emf.
>>> The modeling associations article on the elever website did give me some
>>> overview. (http://www.elver.org/hibernate/hibernate_relations.html) But
>>> Is
>>> there a more detailed article available anywhere?
>>>
>>> I am working with the library example
>>> I am trying to map the Writer to books relationshp as OneToMany
>>> relationship.
>>> <eStructuralFeatures xsi:type="ecore:EReference" name="books"
>>> upperBound="-1"
>>>
>>> eType="#//Book" eOpposite="#//Book/author">
>>>
>>> <eAnnotations source="teneo.jpa">
>>>
>>> <details key="appinfo" value="@OneToMany(mappedBy="author",
>>> indexed=false)"/>
>>>
>>> </eAnnotations>
>>>
>>> </eStructuralFeatures>
>>>
>>> But the mapping generated is always of type many-to-many.
>>>
>>> What am I doing wrong?
>>>
>>> Thanks
>>> RJ
>>>
>>>
>>>
>>>
>>>
>>>
>>
>> --
>>
>> With Regards, Martin Taal
>>
>> Springsite/Elver.org
>> Office: Hardwareweg 4, 3821 BV Amersfoort
>> Postal: Nassaulaan 7, 3941 EC Doorn
>> The Netherlands
>> Cell: +31 (0)6 288 48 943
>> Tel: +31 (0)84 420 2397
>> Fax: +31 (0)84 225 9307
>> Mail: mtaal@springsite.com - mtaal@elver.org
>> Web: www.springsite.com - www.elver.org
>
>
--
With Regards, Martin Taal
Springsite/Elver.org
Office: Hardwareweg 4, 3821 BV Amersfoort
Postal: Nassaulaan 7, 3941 EC Doorn
The Netherlands
Cell: +31 (0)6 288 48 943
Tel: +31 (0)84 420 2397
Fax: +31 (0)84 225 9307
Mail: mtaal@springsite.com - mtaal@elver.org
Web: www.springsite.com - www.elver.org
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| Re: modelling associations [message #427627 is a reply to message #427601] |
Tue, 24 February 2009 19:04 |
Rachna Bakhru
Messages: 45
Registered: July 2009 |
Member |
|
|
Thanks a lot , that was very helpful.
"Martin Taal" <mtaal@elver.org> wrote in message
news:gnvvt8$2nq$1@build.eclipse.org...
> Hi RJ,
> As a default Teneo will use join tables for non-containment relations. You
> can disable this by setting this persistence option to false:
> PersistenceOptions.JOIN_TABLE_FOR_NON_CONTAINED_ASSOCIATIONS
>
> When this option is false then you can set a join table for a an
> association by setting the @JoinTable annotation.
>
> As you are new to EMF, a containment relation is a parent-child relation
> whereby the child depends on the parent for its existence. In the library
> example, a writer and book are contained in a library. The writer and book
> relationship in this model is non-containment.
>
> The reason that Teneo (as a default) uses join tables for non-containment
> relations is that this is safer (less change on name clashes) when having
> very complex models with multiple inheritance.
>
> gr. Martin
>
> RJDAG wrote:
>> Thank you for the quick response.
>>
>> I found the cascadenotall example on the elver website:
>> http://www.elver.org/hibernate/ejb3_examples.html
>>
>> I wish to generate an hbm like
>> CascadeNotallAction_mysql_a_o_hibernate.hbm.xml but when i generate it
>> I get hibernate.hbm.xml.
>>
>> I do not want to use the write_books table to store theWriter to books
>> relationship.
>>
>> Thanks
>> RJ
>>
>> "Martin Taal" <mtaal@elver.org> wrote in message
>> news:gnv6a3$7ld$1@build.eclipse.org...
>>> Hi RJ,
>>> There is no more detailed article available then what is available on
>>> elver.org or the hibernate manual (or posts on the
>>> newsgroup).
>>>
>>> In this case there is a many-to-many present in the mapping, but it has
>>> the special attribute unique="true", which means
>>> it is in fact a one-to-many. A OneToMany annotation can still be mapped
>>> with a many-to-many in hbm (as long as it has
>>> unique="true"). See these parts of the hibernate manual:
>>> http://www.hibernate.org/hib_docs/reference/en/html/assoc-un idirectional-join.html
>>> http://www.hibernate.org/hib_docs/reference/en/html/assoc-bi directional-join.html
>>>
>>> Note that support for Teneo is given on the EMF newsgroup which I cc-ed.
>>>
>>> gr. Martin
>>>
>>> RJDAG wrote:
>>>> Hello
>>>>
>>>> I am new to Teneo and Emf.
>>>> The modeling associations article on the elever website did give me
>>>> some
>>>> overview. (http://www.elver.org/hibernate/hibernate_relations.html) But
>>>> Is
>>>> there a more detailed article available anywhere?
>>>>
>>>> I am working with the library example
>>>> I am trying to map the Writer to books relationshp as OneToMany
>>>> relationship.
>>>> <eStructuralFeatures xsi:type="ecore:EReference" name="books"
>>>> upperBound="-1"
>>>>
>>>> eType="#//Book" eOpposite="#//Book/author">
>>>>
>>>> <eAnnotations source="teneo.jpa">
>>>>
>>>> <details key="appinfo" value="@OneToMany(mappedBy="author",
>>>> indexed=false)"/>
>>>>
>>>> </eAnnotations>
>>>>
>>>> </eStructuralFeatures>
>>>>
>>>> But the mapping generated is always of type many-to-many.
>>>>
>>>> What am I doing wrong?
>>>>
>>>> Thanks
>>>> RJ
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>> --
>>>
>>> With Regards, Martin Taal
>>>
>>> Springsite/Elver.org
>>> Office: Hardwareweg 4, 3821 BV Amersfoort
>>> Postal: Nassaulaan 7, 3941 EC Doorn
>>> The Netherlands
>>> Cell: +31 (0)6 288 48 943
>>> Tel: +31 (0)84 420 2397
>>> Fax: +31 (0)84 225 9307
>>> Mail: mtaal@springsite.com - mtaal@elver.org
>>> Web: www.springsite.com - www.elver.org
>>
>>
>
>
> --
>
> With Regards, Martin Taal
>
> Springsite/Elver.org
> Office: Hardwareweg 4, 3821 BV Amersfoort
> Postal: Nassaulaan 7, 3941 EC Doorn
> The Netherlands
> Cell: +31 (0)6 288 48 943
> Tel: +31 (0)84 420 2397
> Fax: +31 (0)84 225 9307
> Mail: mtaal@springsite.com - mtaal@elver.org
> Web: www.springsite.com - www.elver.org
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