JPA Object-Relational Mapping: how to deal with self-related mapping?

Question

ignore the post.
sorry for my stupidity
==
Hello,
Suppose I have a class nemed Group, which can have sub-groups. It is defined like:
@Entity
Class Group{
private int id;
private String name;
private Group parent; //M-1 mapping
The problem is Group is mapped to itself:
child group -- parent group
M : 1
How JPA supports that kind of relationship? Can I put both
@Many-to-One and @One-to-Many over parent field like:
@Many-to-One
@One-to-Many
private Group parent;
Thanks a lot!
Message was edited by:
javasprinter

Answer 1

One possibility could be the following - (included annotation mappings):
@Entity
Class Group{
private int id; // probably should change to Integer to account for null data
private String name;
@ManyToOne
@JoinColumn(name = "PARENT_GROUP_FK")
private Group parent; //M-1 mapping
@OneToMany
@JoinTable ( name = "SUB_GROUPS",
joinColumns = { @JoinColumn(name = "PARENT_GROUP_ID")},
inverseJoinColumns = {@JoinColumn(name = "CHILD_GROUP_ID")}
private List subGroups;
Tables -
Group - columns - id, name, parent_group_fk
Sub_groups - columns - parent_group_id, child_group_id
The above maps a unidirectional relationship from parent group to child groups, but that really isn't a big deal because you can always get the parent from the parent group id.
I'm sure this isn't the best way, but it worked for me. HTH.