Hi,

I am going to write simple programm where I want to store Garages and Cars (garage can have many cars but car can be only in one garage).
I would like to have increment id in both classes but Car should have unique id only within the garage and I'd like to have all cars in one table.

class Garage
Set cars;

class Car
Garage garage;

example:

ID NAME

01 garage1
---------------
01 car1
02 car2
03 car4

02 garage2
-------------
01 car5
02 car6
03 car7

Table CARS:
car1
car2
car3
car4
car5
car6
car7

Is there any solution to this problem?

Thank you

yep.

you've got it pretty much summed up right here


bi-directional relationship. just create a car, give it a garage, then save it. Then, either the DB, or your code, should assign it the next number car and voila :)

for car you'll want a auto-incrementing field to create the id: car1, car2, car3, etc to keep that unique.

your garage table will have an id, fk car id (which is car1, car2, etc) and an index column which assigns each car a unique number for that garage when saved

could you please send me a mapping document? I don't know how to map the bold part...

Thank you

PS: it's important whether it is uni/bi-directional?

something simple just like this in the car table



something like this for the collection mapping in the garage table


read this as well
http://www.hibernate.org/193.html


then, the garage class needs to be in charge of the index column. To add a new car you would:

create a car
fetch the garage
find out what the last indx number was for that garage
assign the next index number to that car
add it to the collection for the garage
save

So I have to do it "manually" and it seems useless in cluster (I don't have cluster :-))