Persistence 1:n

Question

Hey there,
does anybody has an example of how to implement an 1:n relationship.
lets say i got one car with an unknown number of wheels.
in java i would put them into a vector, how do i handle this using the persistence api.
can i handle this by using setMultipleLink() instead of setSingleLink?
Philipp

Answer 1

Hi Philipp,
    The structure of P_CLASS_CAR and P_CLASS_LICENSE looks fine for the 1:n relation you are looking at.
    The setLicense in the car class now has something like:
                      obj.setSingleLink(0, (PersistableEntity) license);
    This means that the 0th posistion has the license objects and since it is a single link, you just put the license object there.
     But if you have multi linked object then the 0th position will have multiple license objects within itself and you need to specify which position will each license go. So inside your for loop, it will be something like this:
for(int i = 0; i < licences.size(); i++)
     obj.setMultipleLink(0, i, (PersistableEntity) license)
Now in the 0th link element of the car object we have a pool of multi linked license objects. And within each link inside this 0th link, we have the specific license objects.
Best Regards,
  Sandeep