Question about the type of JoinColumn.

[Mellon Sun]

In my Entity OAUser.java, I defined this:

@OneToOne
@JoinColumn(name="roleID",referencedColumnName="id")
private OARole role;

In my Entity OARole.java, there are only two field:
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;

private String roleName;

When TOPLink generate tables, the type of column roldID in table OAUser is varchar(255), and the foreign key generation failed, why?

Toplink execute "ALTER TABLE OAUSER ADD CONSTRAINT FK_OAUSER_roleID FOREIGN KEY (roleID) REFERENCES OAROLE (id)" and encounter an error, because the roleID column in OAUSER is varchar type and the id in OAROLE is number type.

[Mellon Sun]

It's funny.
After dinner, I try it again. No error any more.
Oh, God.

[Chandra Bhatt]

Seems it was waiting for your dinner. You did that, your problem solved.
Would you share what exactly it was?

[Mellon Sun]

I get the difference.
Won't work:
@OneToOne
@JoinColumn(name="roleID",referencedColumnName="id")
private OARole role;

Works well:
@OneToOne
@JoinColumn(name="roleID")//,referencedColumnName="id")
private OARole role;

I don't know why yet.

[Amandeep Singh]

Works well:
@OneToOne
@JoinColumn(name="roleID")//,referencedColumnName="id")
private OARole role;

I don't know why yet.

Can you confirm in your database, whether roleID has a join with any column or not? If yes with which Column?

[Mellon Sun]

I am sure when annotated like:

@OneToOne
@JoinColumn(name="roleID",referencedColumnName="id")
private OARole role;

the OAUSER table will generate but the column roleID is defined as varchar(255) and no Foreign Key constraint is defined for the column roleID.

if erase the attribute referencedColumnName="id":

@OneToOne
@JoinColumn(name="roleID")//,referencedColumnName="id")
private OARole role;

the roleID column in table OAUSER is defined as number(19) and a Foreign Key constraint is defined for the column roleID as well. My program goes
on and insert one row in each table.

[Mellon Sun]

"If you are joining on something other than the primary-key column
of the ADDRESS table, then you must use the referencedColumnName( ) attribute.This referencedColumnName() must be unique, since this is a one-to-one relationship." I find this in "Enterprise Java Beans 3.0", it seemed that I misunderstand the referencedColumnName attribute. In my case, the roleID in OAUser is a foreign key reference the OARole table's id column which is defined as PK of OARole table.

[Karnati Sudhakar]

How come the below code given in EJB in Action is working and the above is not working?

@Entity
@Table(name="USERS")
public class User {
@Id
@Column(name="USER_ID")
protected String userId;
...
@OneToOne
@JoinColumn(name="USER_BILLING_ID",referencedColumnName="BILLING_ID", updatable=false)
 
protected BillingInfo billingInfo;
}
@Entity
@Table(name="BILLING_INFO")
public class BillingInfo {
@Id
@Column(name="BILLING_ID")
protected Long billingId;
...
}

I dont see any difference between the above code and code posted by mellon sun.

Regards
Sudhakar

[Mellon Sun]

No difference edition doesn't work in my NetBeans6.5 before I comment that referencedColumnName="BILLING_ID" attribute ("roleID" in my code).

[Karnati Sudhakar]

No difference edition doesn't work in my NetBeans6.5 before I comment that referencedColumnName="BILLING_ID" attribute ("roleID" in my code).

are you saying that this is a problem with the Netbeans version?In that case i would say no because i am using Netbeans 6.0 and i am facing the same problem you faced(uncommenting referencedcolumnName worked for me).

Regards
Sudhakar

[Mellon Sun]

I am not saying it's wrong of NetBeans6.5.
I prefer to say the book given a mistake sample.