Re: DOM and Database

Hi Rickard,
right now to get things going I am modeling without a focus on persistance. I am retrieving my entities and aggregates on each service call from "repositories". I read
that Hibernate does provide "caching" so maybe I am good with this approach....
Many Greetings
John

--- In [email protected], Rickard Öberg <rickardoberg@...> wrote:
>
> On 5/14/13 14:13 , j.vieten wrote:
> > Hello,
> > I am very new to DDD...
> > Many examples I have seen so far more or less reconstruct their Domain
> > Object Model (DOM) on every service call. In the following "persistence"
> > could be Hibernate or even just jdbc
> > So the flow is
> > 1) service call A
> > 2) "persistence" goes to DB and constructs the needed DOM
> > 3) DOM returns result to service A
> > 4) service call B
> > 5) "persistance" goes to DB and constructs again the needed DOM
> > 6) DOM returns result to service B
> > ...
> > But I would much prefer the following:
> > 1) At the beginning of my application I construct a DOM which can answer
> > all server requests.
> > 2) service call A
> > 3) DOM returns result to service A
> > 4)service call B
> > 5) DOM returns result to service B
> > ....
> > Since in most of the examples I `ve seen the first approach seems to be
> > mostly used....
> > Is there something wrong with using
> > the second approach together with a persistence framework? Or is it just
> > not practical for a enterprise application?
> 
> This depends a lot on whether your app is clustered or not, i.e. if it 
> is the same server that gets write requests. You can always add caching 
> of the constructed DOM, and if you know you're the only write point 
> (e.g. you are using master/slave setup), then it is easy. If you have 
> multi write, then you might have to do at least a version check of your 
> cached object before continuing. OR, you can assume that it is fine and 
> do the write, and on commit when you get versioning errors you can 
> reload and retry.
> 
> It. All. Depends.
> 
> /Rickard
>




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