Hi Rahul,
I suspect the null context value is our implementation but will look
into that tonight. If we cannot figure out, I do appreciate your
offering another set of eyes. My 'helper' had originally stored the
executor per client type and not per client, hence the concurrency
issue... I think we got it sorted:
private SCXMLExecutor getExec(String clientIdentifier){
SCXMLExecutor
exec=(SCXMLExecutor)scxmlExecutorStore.get(clientIdentifier);
if(exec==null){
try {
exec = new SCXMLExecutor(engine,new SimpleDispatcher(),
new SimpleErrorReporter());
exec.setSuperStep(true);
exec.setStateMachine(scxml);
scxmlExecutorStore.put(clientIdentifier,exec);
}catch (ModelException me){
me.printStackTrace();
}
}
return exec;
}
Thanks and I will look at those use cases. I had figured you must've
designed for more than a single threaded use.. After all, what if I want
to control all 10 of my microwaves at once! :-)
Mike
-----Original Message-----
From: Rahul Akolkar [mailto:[EMAIL PROTECTED]
Sent: Tuesday, December 13, 2005 12:39 PM
To: Jakarta Commons Users List; [EMAIL PROTECTED]
Subject: Re: [SCXML] Concurrent users
On 12/12/05, Mike Sparr - www.goomzee.com <[EMAIL PROTECTED]> wrote:
> Rahul,
>
> Your code worked (from your personal snapshot) fine - thanks.
<snip/>
OK, thanks for the update :-)
> One issue
> we're now facing is handling concurrent users from multiple clients.
> My goal is to use one scxml doc to manage app flow for all users.
<snap/>
Indeed, there will usually be only one SCXML document for a particular
application task (or flow, or dialog) -- which could be of arbitrary
granularity -- yet the per user (or per session) "instances" of the
state machine must be able to execute independently.
> It looks
> like there is one context and it's shared, so if we trigger an event,
> it will affect any user.
<snip/>
Each user should have a separate Commons SCXML engine (or more
precisely, an instance of the org.apache.commons.scxml.SCXMLExecutor
class) assigned, and the events must be channeled to the appropriate
engine for the same user/session.
> We have created a HashMap (in memory) to store
> key/handle to client for sending response, but are having troubles
> dealing with concurrent users and their state.
>
> For example:
>
> Web request (state 1, event 3)
> IM request (state 2, event 1)
>
> Can the engine handle that or do you know how best to implement? My
> thought was to store state and last event per user, then navigate to
> that somehow for their requests. I assume there must be a better way?
>
<snap/>
We have a couple of published Commons SCXML usecases here:
http://jakarta.apache.org/commons/sandbox/scxml/usecases.html
Both the usecases are examples within a servlet container environment
(so similar to what you're attempting), and the SCXMLExecutor instance
gets created when needed, then cached and retrieved from the user's
session.
To summarize:
* A SCXML document describes the state machine for a task/flow/dialog
in an application.
* The org.apache.commons.scxml.model.SCXML class is the representation
of the document using the Commons SCXML Java object model.
* An appropriately configured SCXMLExecutor instance creates a "live"
state machine (or engine) upon which external events may be fired.
* SCXMLExecutor instances must be created per user/session and cached
throughout the life of the task/flow/dialog.
-Rahul
> Thanks,
>
>
> Mike
>
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