[rules-users] Re: rules-users Digest, Vol 28, Issue 19

[Ricardo Gil Alcañiz]

Thanks for your fast response Kris and Michal!

I tried to use your solution Kris, but I've found that 5.0.0 M5
WorkflowProcessInstance does not seems to provide getVariable method. I've
found that method into WorkflowProcessInstanceImpl searching in svn trunk. I
must work with that class or I missed something? Thanks again!

Ricardo.


> ---------- Mensaje reenviado ----------
> From: Kris Verlaenen <Kris.Verlaenen at cs.kuleuven.be>
> To: Rules Users List <rules-users at lists.jboss.org>
> Date: Sun, 8 Mar 2009 03:56:29 +0100
> Subject: Re: [rules-users] Drools Flow, constraint parametrization
> Ricardo,
>
> If you need to access process variables and have only simple constraint
> expressions, I suggest you use code constraints (Java or MVEL dialect),
> as they have direct access to variables (and globals).
>
> If you want to use rule constraints anyway (because your constraints can
> become rather complex), there are a few options:
>
>  - You cannot use globals to pass information used in your constraints,
> because globals are considered immutable with respect to rule conditions
>
>  - You can put your data you want to access in your working memory.
> Rule constraints can then access this info just like any normal rule.
>
>  - You access the variable value using the special "processInstance"
> rule constraint (I just added a new section in the documentation to
> explain):
>
> Rule constraints do not have direct access to variables defined inside
> the process. It is however possible to refer to the current process
> instance inside a rule constraint, by adding the process instance to the
> working memory and matching to the process instance inside your rule
> constraint. We have added special logic to make sure that a variable
> "processInstance" of type WorkflowProcessInstance will only match to the
> current process instance and not to other process instances in the
> working memory. Note that you are however responsible yourself to insert
> (and possibly update) the process instance into the session (for example
> using Java code or an (on-entry or on-exit or explicit) action in your
> process). The following exampleof a rule constraint will search for a
> person with the same name as the value stored in the variable "name" of
> the process:
>
> processInstance: WorkflowProcessInstance()
> Person( name == ( processInstance.getVariable("name") ) )
> # add more constraints here ...
>
> Kris
>
> Quoting Ricardo Gil Alcañiz <rgil at okode.com>:
>
> > Hi,
> >
> > I'm not a new drools user but I started to test rule flows (5.0M5)
> > recently
> > and I'm stucked, so any clue will be welcomed :). I'm testing how to
> > share a
> > StatefulKnowledgeSession between N rule flow instances. I'm trying
> > to
> > parametrize each instance with process variables at start time but I
> > don't
> > know how to use them from rule constraints (in event waits, splits,
> > etc.).
> > I've read the documentation and I've found this text related to
> > constraints
> > "Both rule and code constraints have access to globals that are
> > defined for
> > the process and can reuse imports at the process level." I tried it
> > assigning (from an action) a variable value to a global variable but
> > it's
> > not working for me. ¿I'm missing something?
> >
> > Thanks in advance!
> >
> > Ricardo.
> >
>
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