Hi,

I was wondering what's the best way to check if a value exist in another table before doing an insert.

For example, I have something like:

@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
public class A
{
String name
String lastname
String group
}

@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
public class B
{
@Id
group
}

Table B is fully populated and I would like Table A to throw a foreign key constraints if the value in Table A group does not exist in Table B.

Is there a way to do this with some kind of linking? and how would I link it if possible?

Thanks

ManyToOne or OneToOne associations should help you - have a look at the doco -
http://docs.jboss.org/hibernate/stable/ ... tions.html

and a good explanation here:

http://www.neeraj.name/2005/05/05/hiber ... ction.html

Thanks for the responds! It lead me in the right directions. Guess I was afraid the linking would generate the value in class B also but if you only set it on the class A side and not have the class B link to class A then everything is good.

I was able to do it this way:

@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
public class A
{
String name
String lastname
@ManyToOne
@JoinColumn(name="group")
B b//String group
}

@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
public class B
{
@Id
group
@OneToMany(mappedBy="group")
Set<A> a;
}