There's no requirement that they be singletons, but there is some
cost to instantiating a RollerImpl in terms of object creation and
reading the Hibernate mapping files is costly, so we don't want to do
that more than once if we can help it.
- Dave
On Jan 4, 2006, at 5:12 PM, Allen Gilliland wrote:
i've been wondering, is there a reason why all of our manager objects
are restricted to singletons? the way the RollerImpl and
HibernateRollerImpl classes keep a reference to only a single
instantiation of each manager class seems strange to me. most, if not
all, of those classes do not maintain any state and should be safe for
multiple instantiations, so is there a reason why we use singletons
instead?
my main worry is that our current manager classes all seem to have
public constructors, so if they really *should* be singletons then we
aren't really enforcing that. anyone who wants to can simply
construct
a new HibernateWeblogManagerImpl() rather than using the Roller
interface. i think that if a class needs to be a singleton then it
should have a private constructor and a public getInstance() method to
ensure that the class cannot be instantiated more than one time.
this isn't causing any problems, but i noticed it as i was working on
the new ReferrerQueue which is required to be a singleton and i just
thought i'd bring it up as a question of coding practices.
-- Allen
