On Tuesday, January 21, 2003 at 09:27:59 (-0600) Gelhar, Wallace J. writes:
>Bill,
>
>You are trying to treat the name column as a PK which it is not. If you
>assign the same food object (same object id and PK) to multiple objects
>through a M:N association OJB will only store on row in the food table.
>
>The "solution" you are looking for is to look up the food object in the
>table (or create with PK) prior to assigning the food to a person.
Thanks Wallace. Is there no way to make the name column a PK and have
this work 'automatically'? When I tried this, I was getting errors of
the sort 'duplicate key', which indicates that OJB is trying to do the
insert without determining if it needs to.
The problem is, I have an intermediate table that also needs to be
updated. I need to associate the Fish to the Gourmet.
So, the pseudo code that would handle the cases I need might look like
this:
// get a fish, might already exist in DB
Fish fish = get_fish();
// get a gourmet, it also might already exist,
// and it may or may not already be associated with
// the fish above.
Gourmet gourmet = get_gourmet();
if (fish_is_not_in_DB) {
if (gourmet_not_in_DB) {
// neither fish nor gourmet is in db, so we just store
gourmet.add_fish(fish);
store(gourmet);
} else {
// the gourmet is already in the db but not the fish
// (and therefore, the gourmet is not associated with this
// new fish)
store(fish);
// now, what do I do here? How do I create the relationship
// between the newly stored fish and the gourmet already
// in the DB?
} else {
if (gourmet_not_in_DB) {
// The fish is already in the db but not the gourmet
// and also again, therefore, the association
store(gourmet);
// how do I associate the new gourmet and the existing
// fish?
} else {
// here, both gourmet and fish are already in the
// DB. It is possible that they are NOT already
// associated with one another through the intermediate
// table.
if (gourmet_is_NOT_associated_with_fish) {
// perform association
} else {
// do nothing, we have both gourmet and fish and
// they are properly associated
}
}
}
I don't mean to complain, but it seems like it should be possible to
simply do:
Fish fish = get_fish();
Gourmet gourmet = get_gourmet();
gourmet.add_fish(fish);
store(gourmet);
with OJB doing the work outlined above. Is this unreasonable? I'm
certainly willing to be told so and to do the work myself. Since I'm
new at the O/R concept, I'm just doing the 'seat-of-the-pants' thing
that I naively assume works. If I simply don't understand the limits
of O/R (or OJB) then I need to learn them.
Thank you again for your help.
Bill
--
To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]>
For additional commands, e-mail: <mailto:[EMAIL PROTECTED]>
