I searched on the web but cannot filter out the solution. I get pointed
to Spring and Hibernate but I am only interested in the solution with
OpenJPA.
I have a table in which I store the taxonomy tree. The key is the
TAXON_ID and it is linked with its parent through the PARENT_ID. I
created the following DTO named TaxonDto (I left out the fields that are
of no importance):
@Column(name="PARENT_ID")
private Long parentId;
@Column(name="RANG", length=3, nullable=false)
private String rang;
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="TAXON_ID", nullable=false, unique=true, updatable=false)
private Long taxonId;
@OneToMany(cascade=CascadeType.ALL, fetch=FetchType.EAGER,
targetEntity=TaxonnaamDto.class, orphanRemoval=true)
@JoinColumn(name="TAXON_ID", nullable=false, updatable=false,
insertable=true)
@MapKey(name="taal")
private Map<String, TaxonnaamDto> taxonnamen = new HashMap<>();
@OneToOne(cascade=CascadeType.ALL, fetch=FetchType.LAZY,
targetEntity=TaxonDto.class, orphanRemoval=true)
@JoinColumn(name="PARENT_ID", referencedColumnName="TAXON_ID",
updatable=false, insertable=false)
private TaxonDto parent;
My problem lies in the @OneToOne. I did a test with FetchType.EAGER but
then the size of the returned data is 3x bigger as with LAZY since I get
all parents below the taxon. What I want is that the parent is fetched
when the rang is a specific value namely 'oso'. I can live with a
solution where the parent is not recursivly filled, the parent of the
parent in this DTO must be null.
Is this possible and if so how can I do this? I have seen
discriminators, fetchgroup and subclass DTO but it leaves me clueless.
