Need help with Hibernate? Read this first:
http://www.hibernate.org/ForumMailingli ... AskForHelp

Hibernate version: 2.17

Mapping documents:

Code between sessionFactory.openSession() and session.close():

Full stack trace of any exception that occurs:

Name and version of the database you are using:

The generated SQL (show_sql=true):

Debug level Hibernate log excerpt:

It is a general question: what are the general guidelines to decide if an association should be a uni or bi?

For example I have an Employee table which has location_id as a column which refers as a foreign key to location_id in Location table. So
public class Employee implements java.io.Serializable {
private int employeeId;
private Location location;
...
}

If I define Location class why should I include a reference to Employee?
private Set employees;

It depends on the usecase(s) and on the way you want to travel the object graph. If you want to obtain a set of employees associated with a specific location you can fire an hql query on Employee with location as an argument.
If you make the association bidirectional you can do .