Re: Mapping a Join Table with Additional Columns

[Marco de Booij]

The problem is that the join-table has a field (AUTEUR_TYPE) that I need 
to fill. With the ManyToMany I do not have this possibility.

Regards,
Marco

Op 27-04-15 om 13:35 schreef Mark Struberg:
Why don’t you use a @ManyToMany relation?

LieGrue,
strub


Am 26.04.2015 um 17:57 schrieb Marco de Booij <marco.developm...@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