Daos can be useful in certain contexts. In particular, if you have
some means of automagically generating the dao. :)
For instance, on a Tapestry5 + hibernate-based project I'm working on
right now, there's a DaoSource service.
What's more, is there's an @InjectDao annotation that plays nicely
with T5's pages and components.
So you can do something like:
@InjectDao(User.class)
Dao<User> userDao;
public List<User> getAllUsers() {
return userDao.listAll();//or something like this.
}
The key piece being the fact that Dao<User> wasn't code you have to
write (or even generate).
It can make things convenient, but, like Michael and John, I tend away
from Dao's.
Robert
On Mar 30, 2010, at 3/304:26 PM , John Armstrong wrote:
My latest project has a lot of DAO going on and while it made sense
(for
some reason, habit?) at first I regret going that way and will, over
time,
be migrating into the same pattern that Michael highlights. Its
really just
a big useless layer for all the reasons he highlights, at least in my
context.
John-
On Tue, Mar 30, 2010 at 2:20 PM, Michael Gentry
<[email protected]>wrote:
Hi Mike,
I personally tend to not create DAOs for Cayenne. If I need a
findBy*
type method, I just add it to the Cayenne-generated class as a static
method. (For example, I have a User.withUsernameAndPassword() static
method in my User class.) For findById, you can use DataObjectUtils
directly if you like:
http://cayenne.apache.org/doc/api/org/apache/cayenne/DataObjectUtils.html
(objectForPK)
Of course, this is just what I tend to do. Your mileage and that of
others will likely vary. To me, part of the concept of the DAO is
that you can transparently and magically change the DAO code to use a
different ORM and if everything else is using the DAOs, it'll all
just
work. Of course, the assumes that every single ORM works exactly the
same way (they don't) and it also means you are choosing your ORM for
failure (because you expect the need to swap them out). Cayenne
works
differently than Hibernate which works differently than other
ORMs. I
choose an ORM for the features it gives me. To me it doesn't make as
much sense to code with the DAOs (especially when they limit the use
of your ORM), but I'm sure others will disagree with me. :-)
mrg
On Tue, Mar 30, 2010 at 4:51 PM, <[email protected]> wrote:
When using Cayenne are DAO's still the pattern used for findAll,
findByProperty, and findById query methods or is there some better
way to
do this in Cayenne? For example in the pet store project I see
DAO's
being implemented, but I know that example was taken from other
projects
that use DAO's to begin with so I'm not sure if it was just
retrofitted
to
use DAO's with Cayenne. I tried to look at some other examples
from the
website, but most of those are either not complex enough to
warrant that
kind of structure or the links are dead. I hope this is
clear. :) Also
if DAO's are the recommended pattern to use is there a tool (i.e.
eclipse
plugin) that will generate them?
Thanks.
-Mike
