I have Parent/Child relationship in a single-table, let's say as simple as
id | parent_id | some_data
I am trying to understand / implement best practices how to build Hibernate classes for single table relationship.
I have a feed that comes from somewhere and it has nested JSON structure, so after parse it I want to have it representation in OracleDB.
Feed looks like
{
1:
=> 2:
=> 3
=> 4:
=> 5
=> 6
}
this data should end up in db as :
1 | 0 (main rec, no parent)
2 | 1
3 | 2
4 | 2
5 | 4
6 | 1
And it could go deeper and deeper...
I would like to traverse JSON structure and build classes that at the end I save in db
session.save(parent)
parent would be instance of my hibernate mapped class, lets name it Feed.
Each time I descend a tree, it creates a new Feed, finds it's parent and add it to the list.
Feed **parent** = new Feed();
-> Feed child2 = new Feed();
child2.setParent(parent)
parent.add(child2);
-> Feed child3 = new Feed();
child3.setParent(child2)
child2.add(child3);
Feed child4 = new Feed();
child4.setParent(child2)
child2.add(child4);
.............
session.save(**parent**)
My question is could I use @ManyToOne and @OneToMany approach?
I also looked at @Inheritance(strategy = InheritanceType.SINGLE_TABLE) but I do not think I could apply it to my problem since I do not know parents, they are dynamic. I could not build parent class and extend it.
So bottom line I am trying to solve two problems
Easy save on a parent level
How to get data from a parent to a leaf when I need it
Some Hibernate Mapped Classes example would be very appreciated.
Seems like all I needed to do is:
@Entity
@Table(name = "table_name")
public class TableName{
......
@Transient
private Long parentId;
......
@ManyToOne(fetch = FetchType.LAZY, optional=true)
@JoinColumn(name="parent_id")
private TableName parent;
@OneToMany(mappedBy="parent", fetch = FetchType.LAZY, cascade = CascadeType.ALL, orphanRemoval=true)
private Set<TableName> children = new HashSet<TableName>();
Than simply
TableName papa = new TableName();
papa.setParent(null); // parent
TableName kid1 = new TableName();
kid1.setParent(papa);
papa.getChildren().add(kid1);
TableName kid1_1 = new TableName();
kid1_1.setParent(kid1);
kid1.getChildren().add(kid1_1);
TableName kid2 = new TableName();
kid2.setParent(papa);
papa.getChildren().add(kid2);
session.save(papa)
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