updateable resultset only working for tables?

First i tried to update/insert records using an updateable resultset using a
table as datasource, that works just fine.

My application requires to do updates also to views which are created about as
this:

create view sometable_update as Select * from sometable;
create rule sometable_update_rule as on update to sometable_update do instead
update sometable set ...;

Updating to sometable_update does work if i type an update statement myself.

However, using code like this:

Statement stmt=conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,
ResultSet.CONCUR_UPDATABLE);
ResultSet urs=stmt.executeQuery("SELECT * FROM sometable_update");

results in an SQLException "no primary keys".

Basically i assume, that this happens because the driver is not able to detect
the primary keys of a view, which is mainly because postgres stores views in
a completly different way as tables.

Is there a way to tell the driver the primary keys manually (as i know them at
this point in my code) for a certain ResultSet/Statement or another solution
to this problem?

If possible i would like to avoid creating my own insert/update-Strings and
let it do the driver.

Guido