about one to one

[David Wong]

are there two strategies of mapping for <one-to-one/> ?one is primary key mapping strategy other is foreign key mapping strategy.what's the advantage in each of them?

if i have a construction of db below:

table a
id int primary key
name varchar

table b

id int primary key
a_id int foreign key(a_id) references a(id)

how could we use the two strateies to get one a to one b.what are the differences?

thanks very much!!

[Cameron Wallace McKenzie]

I'm not sure how you're using the term one-to-one here?

To map one table to one class, is fairly straight forward. You can just use the @Entity annotation:

Mapping One Class to One Table

But you mentioned using a shared primary key? So this would be two classes to one table? You can use the @Embedded and @Embeddable annotations to accomplish this:

Mapping Two Classes to One Table Using Hibernate and JPA Annotations

But then you mention foreign keys? So you may have two tables related by a foreign key mapping to one class? In this case you're looking at using the @SecondaryTable annotation

Mapping One Class to Two Database Tables using Hibernate and JPA

  
@Entity
@Table(name="bar")
@SecondaryTable(name="foo")
public class FooBar {
  int id;
  String fooName;
  String barCode;   
  @Id
  @GeneratedValue
  public int getId() { return id;}
   
}  

Is that what you were getting at?

-Cameron McKenzie