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From "Kevin Menard" <>
Subject Re: Call a service, but still with one DataContext
Date Tue, 12 Aug 2008 11:12:21 GMT
Ahh . . . I misunderstood what you were trying to do.
It sounds like you are indeed looking to use the three tier (ROP)
architecture.  In this case, you will want to use Cayenne in its server
capacity.  It should have little bearing on the rest of your Web app,
however.  Cayenne comes with a servlet that you can set up in your web.xml
[1].  Multiple servlets can exist in the same Web app . . . just bind them
to different URLs.

Context management gets a little trickier, but you're probably most
concerned with the client level of things.  In that case, just create a
CayenneContext per user session in your Swing app.

Apologies also for the shorthand.  WS = Web Services.

[1] --


On Mon, Aug 11, 2008 at 9:16 PM, Chris Murphy <> wrote:

> Hi Kevin,
> I'm coming from JDO which has PersistenceManager instead of a DataContext -
> but they should be conceptually the same thing. I am interested in using
> Cayenne over a client/server connection from a Swing front end. Hence
> there's a proxy-DataContext that the Swing client will be communicating
> with? I imagine the part that runs on the server that handles the client
> requests normally runs as a servlet? My issue is that as Spring also runs as
> a servlet, how can both servlets use the same DataContext?
> It has been a long time since I've done any servlet or Spring configuration
> - so do let me know if any of the assumptions I've just made are wrong.
> From what you say: "bind your DataContext to the user session" - is the
> answer to lazily load the DataContext from the Session enabling both the
> servlets to have access to the same DataContext - by always finding it
> through the Session object?
> thanks - Chris
> PS./ What's a WS server? Is that a 'web service'?
> Kevin Menard wrote:
>> Hi Chris,
>> I'm not really sure I understand your question.  I think you're slightly
>> confused by our nomenclature.  Cayenne server really is just a plain Java
>> package.  The server part comes from a three-tier role, where we have a
>> separate client package.  In this case, you'd run some sort of WS server
>> to
>> handle the client requests.  Otherwise, you can use the "server" package
>> in
>> any app.
>> Viewed that way, you're best bet is probably to use the servlet filter and
>> bind your DataContext to the user session.  This should ensure that you
>> only
>> have one DC per user.  From there, you just need to apply basic principles
>> for using a single DC.  In particular, don't get messy with uncommitted
>> state.
> --
> Seaweed Software Pty Ltd,

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