Many to many plus additional value

[chrismalan]

This question has been asked at least twice. The answer is: "use an intermediate entity to represent your assoc table"

I looked but could not find much on this in the Hibernate documentation. It is most likely where I did not look.

I have an idea of what to do, but do not know if it right.

Take the JBoss Flights_Customers example. Say I want to add another column named Date to the join table.

Do I do this:

@Entity
public class Flights_Customers{
 private String flight, customer;
 private java.sql.Date date;

and then in Flight

@JoinTable(
 table=@Table(name="Flights_Customers"),
 joinColumns={@JoinColumn(name="flight")},
 inverseJoinColumns={@JoinColumn(name="customer")}

In Customer the joinColumns and inverseJoinColumns swap over. I use a few more annotations to set up the join, but this is what is relevant.

Is this how it should be done? If not, what should be done differently?

Thanks,

[alximik]

Try this

@Entity
public class Flights_Customers{
 @ManyToOne
 private Flight flight;

 @ManyToOne
 private Customer customer;
...........
}

@Entity
public class Customer{
 @OneToMany(mappedBy="customer")
 private Collection<Flights_Customers> flights_Customers;
...........
}

@Entity
public class Flight{
 @OneToMany(mappedBy="flight")
 private Collection<Flights_Customers> flights_Customers;
}

[chrismalan]

Thanks Alximik,

I suppose one will then get all the customers for a flight (or vice versa) straight from the relationship table. I am quite sure this may actually work.

Thanks again.

Chris