Re: Cayenne integration guidelines

[Borut Bolčina <bo...@najdi.si>]

Hi, you got me a bit confused here. See below.

Eric Schneider wrote:

> Borut,
>
> I've always stuck to the simplest approach.  If I'm dealing with a  
> completely stateless application, I share one DataContext for all  
> users (in T4 as a hivemind singleton).   

So each request from browser (user) can change anything in one and only 
DataContext. I imagine there can be such cases where no harm can be done 
to the underlying data.

> For stateless apps, each  individual user has their own DataContext in 
> the Visit object.   

Isn't visit (ASO session) the very definition of stateful application? 
According to HLS: "When a session-scoped application state object is 
first created, or when the first persistent page property is recorded. 
At this point, Tapestry will create the HttpSession to hold the object 
or property.". I don't want a session to be created on my first page. 
Now, I understand in T4 I can have persistent properties and stay 
stateless by storing those properties on client side. I guess this can 
be achieved by using hidden fields but with less comfort.

Consider this scenario:

   1. Page A must collect email and serial number and answers to some
      questions. Based on the email and a number a db look-up must be
      made to see if this "user" already exists (if he/she already
      answered the questions). This can be done by shared (singleton)
      DataContext (I guess by this DataContext context =
      DataContext.getThreadDataContext();)
   2. If the user exists, get this User DataObject and if it doesn't
      create one. In either case pass DataObject to page B via bucket
      brigade pattern.
   3. On page B edit some of the DataObject's properties in text fields,
      validate them and consequently save them along with the data
      collected on page A which were passed on page B also (user's
      answers). If users existed an UPDATE must be made, if not an
      INSERT. An update is made if DataObject is in CHANGED state, so
      the DataContext into which this existing user was fetched in on
      page A must be the same as this DataObject's properties are being
      edited on page B. And that would be this global DataContext.

Can anyone comment please?

> I  haven't used the CayenneDataSqueezer, simply because I haven't had 
> to  yet (though, I understand it's extremely useful).
>
> My object entities tend to be a bit wide, so they're not something  
> I'd typically squeeze into a direct link for example (really long  
> urls can lead to undesired results w/some browsers).   More often I  
> squeeze the object's ObjectId on actions related to specific data  
> objects.
>
> Hope that helps.
> Eric
>
> On Oct 24, 2005, at 5:27 PM, Borut Bolčina wrote:
>
>> Hi,
>>
>> I searched through the archives and read all that I could about  
>> integrating Cayenne with Tapestry. The latest thread "Tapestry,  
>> Cayenne and Squeezer" was informative, especially Filip's post  which 
>> is on wiki also. All other posts were a bit out of date I  think 
>> dealing with T3. Although reading about cayenne squeezer did  light 
>> some bulbs (ok, more of a flickering that is) I felt insecure  about 
>> how to get started.
>>
>> I guess it boils down to whether you go stateless or not? In the  
>> former case one should use ASO session scoped object (visit) and if  
>> you want to stay stateless, than you should use all the help from  
>> CayenneDataSqueezer. Is that correct?
>>
>> Are there  T4 & Cayenne (stateful, stateless or both) examples  (best 
>> practices) somewhere I missed?
>>
>> Regards,
>> Borut
>>
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>
>
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Re: Cayenne integration guidelines

[Neil Pierson <ne...@gmail.com>]

I'm sure Eric meant 'stateful' instead of 'stateless'.

On 11/1/05, Borut Bolčina <bo...@najdi.si> wrote:
>
> Hi, you got me a bit confused here. See below.
>
>
> > For stateless apps, each individual user has their own DataContext in
> > the Visit object.
>
> Isn't visit (ASO session) the very definition of stateful application?
> According to HLS: "When a session-scoped application state object is
> first created, or when the first persistent page property is recorded.
> At this point, Tapestry will create the HttpSession to hold the object
> or property.". I don't want a session to be created on my first page.
> Now, I understand in T4 I can have persistent properties and stay
> stateless by storing those properties on client side. I guess this can
> be achieved by using hidden fields but with less comfort.
>
>
>
>