Re: [eclipselink-users] question about one-to-many

[Jan Kriesten <jan.kriesten@xxxxxxxxxxxx>]

Hi Zachary,

> I do not believe that unidirectional @OneToMany mapping without a join
> table is supported by the JPA1.0 spec.

that's strange, EJB 3.0 suggests that it should be possible with the XML I
posted (found that in O'Reilly EJB 3.0 5th Edition). Though I don't really know
for JPA 1.0...

Best regards, --- Jan.


> For JPA1.0 you either need to
> do bidirectional as I suggested before or use a join table (which is
> what the error is complaining about not finding)
> 
> Take a look at
> http://wiki.eclipse.org/EclipseLink/Development/JPA2.0/uni-directional_onetomany_mapping for
> info on support being added to eclipselink.
> 
> -zach
> 
> On Oct 14, 2008, at 11:10 AM, Jan Kriesten wrote:
> 
>>
>> Hi Zachary,
>>
>>> If I'm understanding your question correctly you want a bi-directional
>>> relationship between Zutat and Rezept with Rezept being the owning side
>>> of the relationship.
>>
>> no, that I figured. I want a uni-directional mapping from Rezept 1 ->
>> 8 Zutat
>> (using @OneToMany).
>>
>> Best regards, --- Jan.
>>
>>> Rezept needs to have:
>>>
>>> @OneToMany(mappedBy="rezept")
>>> private List<Zutat> zutats;
>>>
>>> and Zutat needs to have:
>>>
>>> @ManyToOne
>>> @JoinColumn(name="rezid" referencedColumnName="id")
>>> private Rezept rezept;  //note that the field name is what is used in
>>> the 'mappedBy' attribute on the owning side
>>>
>>> Hopefully that helps,
>>>
>>> -zach
>>>
>>> On Oct 14, 2008, at 9:59 AM, Jan Kriesten wrote:
>>>
>>>>
>>>> Hi,
>>>>
>>>> I've an understanding problem using one-to-many:
>>>>
>>>> I've got the following tables:
>>>>
>>>> REZ_REZEPTE:
>>>> id: int
>>>> name: String
>>>>
>>>> REZ_ZUT:
>>>> id: int
>>>> rezid: int
>>>> name: String
>>>>
>>>> Now I want to have a List of all REZ_ZUT in REZ_REZEPTE.
>>>>
>>>> This actually works:
>>>>
>>>> @Entity
>>>> @Table { val name = "REZ_REZEPTE" }
>>>> @serializable
>>>> class Rezept {
>>>> @Id @GeneratedValue
>>>> @BeanProperty var id: Int = _id
>>>> @BeanProperty var name: String = _name
>>>> @OneToMany { val cascade = Array( CascadeType.ALL ), val targetEntity =
>>>> classOf[Zutat], val mappedBy = "rezept" }
>>>> @BeanProperty var zutaten: JList[Zutat] = null
>>>> }
>>>>
>>>> But this needs class Zutat mapping back to 'Rezept'.
>>>>
>>>> It should work to use
>>>>
>>>> @OneToMany { val cascade = Array( CascadeType.ALL ), val targetEntity =
>>>> classOf[Zutat], val fetch=FetchType.EAGER }
>>>> @JoinColumn { val name = "rezid" }
>>>> @BeanProperty var zutaten: JList[Zutat] = null
>>>>
>>>> but that give an error:
>>>>
>>>> Internal Exception: Exception [EclipseLink-7160] (Eclipse Persistence
>>>> Services -
>>>> 1.0.1 (Build 20080905)):
>>>> org.eclipse.persistence.exceptions.ValidationException
>>>> Exception Description: @OneToMany for attribute name [zutaten] in
>>>> entity class
>>>> [class Rezept] should not have @JoinColumn(s) specified. In the case
>>>> where the
>>>> @OneToMany is not mapped by another entity (that is, it is the owning
>>>> side and
>>>> is uni-directional), it should specify (optional through defaulting) a
>>>> @JoinTable.
>>>>
>>>> I tried to use the xml-variant instead (which at least allows to define
>>>> join-columns):
>>>>
>>>>  <entity class="Rezept">
>>>>    <attributes>
>>>>      <id name="id"><generated-value /></id>
>>>>      <one-to-many name="zutaten" target-entity="Zutat" fetch="EAGER">
>>>>        <join-column name="rezid"/>
>>>>      </one-to-many>
>>>>    </attributes>
>>>>  </entity>
>>>>
>>>> But that gives a SQL-Exception - and I really don't know why
>>>> EclipseLink is
>>>> trying to access a table named "rez_rezepte_rez_zut":
>>>>
>>>> Exception [EclipseLink-4002] (Eclipse Persistence Services - 1.0.1
>>>> (Build
>>>> 20080905)): org.eclipse.persistence.exceptions.DatabaseException
>>>> Internal Exception:
>>>> com.mysql.jdbc.exceptions.MySQLSyntaxErrorException: Table
>>>> 'rez_rezepte_rez_zut' doesn't exist
>>>> Error Code: 1146
>>>> Call: SELECT t1.ID, t1.EINHEIT, t1.MENGE_MAX, t1.MENGE_MIN,
>>>> t1.MENGE_ORG,
>>>> t1.NAME, t1.REZID FROM REZ_REZEPTE_REZ_ZUT t0, REZ_ZUT t1 WHERE
>>>> ((t0.Rezept_ID =
>>>> ?) AND (t1.ID = t0.zutaten_ID))
>>>>
>>>> Can someone give me some insight where I'm going wrong?
>>>>
>>>> Best regards, --- Jan.
>>>>
>>>> _______________________________________________
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>>>
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