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

[Kris Verlaenen]

Ricardo,

This method has recently been added into WorkflowProcessInstance, it is on trunk and will be in CR1.  For M5, you could indeed use WorkflowProcessInstanceImpl ...

Kris
  ----- Original Message ----- 
  From: Ricardo Gil Alcañiz 
  To: Rules Users List 
  Sent: Monday, March 09, 2009 4:37 PM
  Subject: [rules-users] Re: rules-users Digest, Vol 28, Issue 19


  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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