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

[Zachary Smith <zach@xxxxxxxxx>]

>

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.  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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