[Seaside] access to the model using goods

[John Pierce]

We use Seaside and GOODS to manage many business objects and we use a
"share none" approach for Seaside client connections -- meaning each
connection gets its own connection to GOODs and maintains its own
objects.  Doing this avoids a myriad of issues surrounding concurrency
when sharing the same object instances.  How we've implemented this is
as follows:

1. We create an accessor on the page class (or you could share a goods
connection in a subclass of WASession)  like the following:

SomeWAComponent>>goodsDb

	^ goodsDb ifNil:
		[goodsDb _ KKDatabase
			onHost: 'dbserver'
			port: 9000]

2. Then we just use the goodsDb method wherever we need it (e.g. when
rendering or updating our business objects on postback).   We find
this to be the best approach overall.

3. Also, at the top of our renderContentOn: loop we do a
  self goodsDb refresh just to keep the objects in their most current
state as another user may have altered the objects during the session.

4. When commiting changes made to the business objects we do them in a
commitWithRetry block handler (on KKConnection).

5. Lastly, we have found that it works best to collect a list of
actions from the seaside app rather than update the objects directly. 
Actions can be as simple as collecting up a bunch of blocks into a
list, where if you were to run the block the result would be to update
the business object.  Why this may seem to be unnecessary
complication, we find that it allows us to correctly handle conflicts
between users in the midst of the commitWithRetry block handler I
mentioned in #4 above.  I can provide a more detailed example of this
if you are interested.

Maybe Avi has a better strategy for "replaying" the changes on
postback to the business objects in a GOODS setting if there where
commit conflicts.  Our "list of actions" approach is pretty easy to
implement and simple, but there might be a built-in approach that I
haven't seen.

Regards,

John



On Tue, 7 Dec 2004 15:42:54 -0300, Leo De Marco <leo at smalltalking.net> wrote:
> Hi everyone!
> 
> I was working with my application using seaside, leaving the persistence problem like the last thing to do...
> So, now is the moment to worried about that. Till now, I have access to my model using a singleton where I have all my collections (Company current). I need to access to the singleton from my seaside "pages" and from the model too.
> When I decided to use GOODS, I put my singleton like the root, so when I need to access from de session of seaside:
> 
> ^self db root
> 
> My problem is with the access from the model... I was thinking about the possibility to access through another connection in the model, but I dont know is the best thing to do....
> Any ideas??
> 
> pd: I dont need performance :)
> 
> Best regards,
> 
> Leo De Marco
> leo at smalltalking.net
> 2004-12-07
> 
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