What is the difference between Unidirectional and Bidirectional associations?
- by hguser
Hi:
What is the difference between Unidirectional and Bidirectional associations?
Since the table generated in the db are all the same,so the only difference I found is that each side of the bidiretional assocations will have a refer to the other,and the unidirectional not.
/////////// This is a Unidirectional association
public class User {
private int id;
private String name;
@ManyToOne
@JoinColumn(
name = "groupId")
private Group group;
}
public class Group {
private int id;
private String name;
}
////////////// The Bidirectional association
public class User {
private int id;
private String name;
@ManyToOne
@JoinColumn(
name = "groupId")
private Group group;
}
public class Group {
private int id;
private String name;
@OneToMany(mappedBy="group")
private List<User> users;
}
The difference is wheather the group hold a refer of the user.
So I wonder if this is the only difference? which is recommended?
