Hi Uden,
If you'd rather keep the relation unidirectional just remove the
`children` field-- the `parent` field alone is enough to encode the
relation without recourse to a separate join table. Either way, I don't
see how the quoted section below results in a join table. Both fields
rely solely on a "parent_id" column within the "ModelObject" table, not
on some other join table. Am I missing something?
Andy
Uden wrote:
The solution quoted below but has a consequence for the Java class model: the
OneToMany relationship becomes bi-directional instead of uni-directional.
What is the reason for creating the join-table?
I thought (based on my database experience) that a join-table is only
required for ManyToMany relationships.
If you look at the data in the join-table of a uni-directional relation (no
mappedBy attribute), the relation between the join-table and master table is
always OneToOne, so this relation could be handled by a FK-field in the
detail-table.
thanks for your explanation,
Uden
Andy Schlaikjer-2 wrote:
Marco Schwarz wrote:
How can I make only 2 tables?
Here's my guess:
First, use the "mappedBy" property of the @OneToMany annotation, like
this:
@Entity
class ModelObject {
...
@ManyToOne
ModelObject parent;
@OneToMany(mappedBy="parent")
List<ModelObject> children;
...
}
This way, an extra join table won't be necessary to encode the parent
child relationship. Only the "parent_id" column in the "ModelObject"
table will be used to encode the relationship.
