accessing cayenne sessions

[Cyp her <cy...@hotmail.com>]

Hi

I am a newbie to Cayenne but I have been developing with WebObjects for a 
few years and though I would try something open source. I have been reading 
a few articles on getting the DataContext namely this one 
http://www.objectstyle.org/confluence/display/CAYDOC/Web+Applications but it 
still leaves me a little bit confused.

My set up is Cayenne with Tapestry deployed to JBoss using Eclipse as the 
development platform. So my questions are

* What is the best way of retrieving the session context (DataContext) on a 
given page and tracking the changes over a workflow and eventually 
committing the changes or discarding them?

* Can I do the same using Tapestry to achieve the same results i.e. are 
there any Tapestry calls for getting the Session

* Are there any convenient methods for accessing the Session like in 
WebObjects where there is a session class in the application?

* I have read some people opt to use Tapestry, Spring and Hibernate. What 
are the advantages if there are any and can you use Tapestry, Spring and 
Cayenne?

Thank you very much for your help and apologies if all the answersw are 
somewhere in this mailing list.

Lawrence

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Re: accessing cayenne sessions

[Mike Kienenberger <mk...@gmail.com>]

On 4/4/06, Cyp her <cy...@hotmail.com> wrote:
> * I have read some people opt to use Tapestry, Spring and Hibernate. What
> are the advantages if there are any and can you use Tapestry, Spring and
> Cayenne?

Probably the number one reason for any WO developer to use Cayenne
instead of Hibernate is because it's similar to EOF and there are many
former (and current) WO developers actively involved in this project,
and we speak the same language and generally do things the same way.

To get started, take a look at this:

http://www.objectstyle.org/cayenne/userguide/misc.html

If you're not sold on Tapestry yet, you might also to evalute the
click framework as another WO-like alternative.

http://click.sourceforge.net/

Re: accessing cayenne sessions

[Andrus Adamchik <an...@objectstyle.org>]

On Apr 4, 2006, at 5:52 PM, Cyp her wrote:

> * What is the best way of retrieving the session context  
> (DataContext) on a given page and tracking the changes over a  
> workflow and eventually committing the changes or discarding them?

Cayenne 1.2 has a WebApplicationContextFilter:

http://objectstyle.org/confluence/display/CAYDOC/Servlet+2.3+Filter

It provides you access to the session DataContext regardless of the  
framework you use (in the past I put it in Tapestry Visit instead,  
but I don't bother anymore, the filter is more portable). If you  
configure the filter per docs page above, you can always get the  
session context anywhere in the app like this:

DataContext context = DataContext.getThreadDataContext();


> * I have read some people opt to use Tapestry, Spring and  
> Hibernate. What are the advantages if there are any and can you use  
> Tapestry, Spring and Cayenne?

Yeah, that's the right place to ask for an unbiased Cayenne vs.  
Hibernate comparison ;-)

Hibernate is an ORM, so conceptually it is similar to Cayenne (and  
EOF). Regarding the differences... Cayenne provides more EOF-like  
experience in managing your object graph. I've heard an opinion from  
a WO user that Hibernate is more like eoaccess (I guess he was  
referring to the fact that you need to manage a number of low-level  
details). In this respect Cayenne is eoaccess+eocontrol (and since  
recently - also EO JavaClient, for those who care). DataContext is  
very similar to EOEditingContext.

IMO when migrating from WO, switching from EOF to Cayenne is a  
relatively minor thing compared to switching WO framework to any  
other web front-end technology.

Andrus

Re: accessing cayenne sessions

[Mike Kienenberger <mk...@gmail.com>]

On 4/4/06, Cyp her <cy...@hotmail.com> wrote:
> * Are there any convenient methods for accessing the Session like in
> WebObjects where there is a session class in the application?

In servlets, there's an HttpSession object that you can pull out of
the HttpServletRequest.   Instead of being a subclassable object, it
instead holds references to a Map (think NSDictionary) where you can
store objects the entire session.  How you get a reference to your
HttpSession object depends on the framework.

http://java.sun.com/products/servlet/2.3/javadoc/javax/servlet/http/HttpSession.html