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From Mark Struberg <strub...@yahoo.de>
Subject Re: Mapping a Join Table with Additional Columns
Date Mon, 27 Apr 2015 11:35:58 GMT
Why don’t you use a @ManyToMany relation?

LieGrue,
strub


> Am 26.04.2015 um 17:57 schrieb Marco de Booij <marco.development@debooy.eu>:
> 
> I use Tomee 1.7.1 with openjpa version openjpa-2.4.0-nonfinal-1598334-r422266.
> 
> I have an entity auteurs and an entity boek. They have a ManyToMany relation through
the entity auteurs_boeken. In this entity there is a field type to define the type of the
relation (writer, illustrations, ...). I followed the https://en.wikibooks.org/wiki/Java_Persistence/ManyToMany
page and came up with the following classes (left out all constructors, getters, and setters):
> 
> =====
> @Entity
> @Table(name="AUTEURS", schema="BYBLOS")
> public class AuteurDto
>    extends Dto implements Comparable<AuteurDto>, Cloneable {
>  private static final  long  serialVersionUID  = 1L;
> 
>  @Id
>  @GeneratedValue(strategy=GenerationType.IDENTITY)
>  @Column(name="AUTEUR_ID", nullable=false, unique=true)
>  private Long    auteurId;
>  @Column(name="NAAM", length=100, nullable=false)
>  private String  naam;
>  @Column(name="VOORNAAM", length=100)
>  private String  voornaam;
> 
>  @OneToMany(cascade=CascadeType.ALL, fetch=FetchType.LAZY, mappedBy="auteur")
>  private List<AuteurBoekDto> boeken;
> }
> 
> =====
> @Entity
> @Table(name="BOEKEN", schema="BYBLOS")
> public class BoekDto extends Dto implements Comparable<BoekDto>, Cloneable {
>  private static final  long  serialVersionUID  = 1L;
> 
>  @Id
>  @GeneratedValue(strategy=GenerationType.IDENTITY)
>  @Column(name="BOEK_ID", nullable=false, unique=true)
>  private Long    boekId;
>  @Column(name="DEEL", precision=5, scale=0)
>  private Integer deel;
>  @Column(name="DRUK", precision=3, scale=0)
>  private Integer druk;
>  @Column(name="ISBN", length=13)
>  private String  isbn;
>  @Column(name="JAAR_UITGAVE", precision=4, scale=0)
>  private Integer jaarUitgave;
>  @Column(name="SUBDEEL", length=2)
>  private String  subdeel;
>  @Column(name="TAAL", length=2, nullable=false)
>  private String  taal;
>  @Column(name="TITEL", length=100, nullable=false)
>  private String  titel;
> 
>  @OneToOne(cascade=CascadeType.ALL, fetch=FetchType.LAZY)
>  @JoinColumn(name="SERIE_ID", nullable=false, updatable=false)
>  private SerieDto  serie;
> 
>  @OneToMany(mappedBy="boek", fetch=FetchType.LAZY)
>  private List<AuteurBoekDto> auteurs;
> }
> 
> =====
> @Entity
> @Table(name="AUTEURS_BOEKEN", schema="BYBLOS")
> @IdClass(AuteurBoekPK.class)
> public class AuteurBoekDto
>    extends Dto implements Comparable<AuteurBoekDto>, Cloneable {
>  private static final  long  serialVersionUID  = 1L;
> 
>  @Id
>  private Long    auteurId;
>  @Id
>  private Long    boekId;
>  @Column(name="AUTEUR_TYPE", nullable=false, length=1)
>  private String  auteurType;
> 
>  @ManyToOne
>  @PrimaryKeyJoinColumn(name="AUTEUR_ID", referencedColumnName="auteurId")
>  private AuteurDto auteur;
>  @ManyToOne
>  @PrimaryKeyJoinColumn(name="BOEK_ID", referencedColumnName="boekId")
>  private BoekDto   boek;
> }
> 
> When I fetch the boeken from within the AuteurDto I get the message:
> <openjpa-2.4.0-nonfinal-1598334-r422266:1599166 fatal user error> org.apache.openjpa.persistence.ArgumentException:
"eu.debooy.byblos.domain.AuteurBoekDto.auteur" defines a target of "auteurId" for column "AUTEUR_ID",
but that target does not exist in table "BYBLOS.AUTEURS".
> I have the same problem on the BoekDto. BoekDto has a OneToOne relation with SerieDto
and when I read the boeken from there I get the correct boeken so I guess that the problem
lies with my implementation of the ManyToMany. Can someone show me the way to the correct
implementation?
> 
> Regards,
> 
> Marco


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