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From "James Strachan" <james_strac...@yahoo.co.uk>
Subject Re: Workflow
Date Tue, 13 Nov 2001 22:36:52 GMT
Hi Colin

Great! Sounds like a neat fit. I've been meaning to really grok the Workflow
project so I should do that now.  I'm interested in putting an example
together at some point, when you've time, that demonstrates Messenger and
Workflow in action together - it sounds cool.

James


----- Original Message -----
From: "*Colin Sharples" <Colin.Sharples@hbl.co.nz>
> Woohoo! That is exactly what I've been looking for. At the moment I've
just
> got my code running in a standalone process which kicks off threads to
> handle the messages. I did want to have it running in a servlet engine,
but
> couldn't be bothered working out how to integrate the message listeners
with
> servlets. Your code seems to be exactly what I need.
>
> Now, as far as integrating Messenger and Workflow, I have some code which
> will probably do the job. It's fairly simple, and boils down to:
>
> 1. A mechanism for mapping activities to messages. This really just
extends
> Craig's Registry mechanism, so that for any given message using a
> combination of the destination and/or message type allows you to identify
> which activity to run on that message.
>
> 2. A mechanism for translating the contents of the message into the
activity
> context. I just defined an interface called ContextPopulator, with one
> method:
>   public Context populateContext(Message) throws JMSException;
> When the activity definitions are being parsed and registered, you also
> create a number of beans which implement ContextPopulator and associate
them
> with the relevant activities.
>
>
> 3. Something which implements onMessage() and does:
>    - populate the context from the message
>    - set the activity on the context
>    - execute the activity
> and also handles other stuff like exceptions (commit or rollback on the
> queue session), checking for poisoned messages etc.
>
> The last bit is the candidate for being a MessageDrivenObject. The servlet
> can handle the registration of the activities and context populators. Hmm.
> Okay, if I get some time I'll see if I can modify my stuff to use
Messenger.
>
>
> Colin.
>
> -----Original Message-----
> From: James Strachan [mailto:james_strachan@yahoo.co.uk]
> Sent: Wednesday, 14 November 2001 12:12 a.m.
> To: Jakarta Commons Developers List
> Subject: Re: Workflow
>
>
> Hi Colin
>
> ----- Original Message -----
> From: "*Colin Sharples" <Colin.Sharples@hbl.co.nz>
> > BTW, I've been working on an implementation of the workflow system,
which
> > definitely rocks. I've created an execution environment based on JMS -
> > activities are triggered by messages arriving on queues. I'm not sure
what
> > the attitude of the client I'm working for is, but I may be able to
submit
> > the generic JMS stuff I've been working on when I'm finished
> (mid-December).
>
> I'm working on a JMS framework called Messenger...
>
> http://jakarta.apache.org/commons/messenger.html
>
> ... which provides a framework for working with JMS and dispatching JMS
> messages to MessageListeners & Servlets & JSP. So, for example, JSP custom
> tag libraries could be used to process JMS messages to perform XPath, XSLT
> or SQL operations etc. It should be quite easy to integrate with the
> existing commons-workflow project.
>
> There could well be some crossover with what you are doing as well with
the
> workflow project. I'd be interested in any thoughts you might have on the
> Messenger project and am interested to hear more of your JMS based
workflow
> system.
>
> James
>
>
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