[rules-users] persistent java objects in working memory

[Greg Barton]

You've answered your own question. :)  The rule you've given will only fire when the object is asserted or modified. (And you have to inform the engine of the modification.)  You have to inform the engine that the object has been modified every cycle. (And if you want the engine to fire that rule even if the object has not been modified, you can still inform the engine.  All that does is force the rules to reconsider the object.)

However, the way I'd do it is to have a new object that is inserted on each iteration.  Let's call it "Cycle" and give it a count. Then your rule would look like this:


rule "Identify Java
Objects"
   lock-on-active
when
   $mo : MyDataObject();
   $c : Cycle();

then
  
System.err.println("MYOBJECT in system: " + $mo.getID() + " |
" + $mo.getTestFieldData() + " on Cycle " + $c.getCount());end 


When the iteration is over, you would retract the Cycle object.  (Only one Cycle should be in working memory at once, and it's a good idea to have a rule that enforces that invariant.)  You should follow this pattern for any rule you want to guarantee to fire on each iteration.



________________________________
From: Chris Richmond <crichmond at referentia.com>
To: Rules Users List <rules-users at lists.jboss.org>
Sent: Wednesday, September 23, 2009 2:15:35 PM
Subject: [rules-users] persistent java objects in working memory

 
Hello,
 
I am trying to create a set of java objects, which I insert
into the session at startup.  Then at regular timed iterations I want to
examine the values of those objects.  During the timer iteration, some
fields may have been changed by the primary program.  So I have a rule for
now that is just trying to identify that the do indeed exist on each iteration:


 
rule "Identify Java
Objects"
   lock-on-active
when
   $mo : MyDataObject();
then
  
System.err.println("MYOBJECT in system: " + $mo.getID + " |
" + $mo.getTestFieldData);
 
end   
 
 
As I said, at startup I insert 3 of these objects into my
session, then every 10 seconds I just want to ensure they are there.  However
the output from this rule only fires on the firet iteration, after that the
rule doesn’t fire.  I am not retrcating the objects or even
concerning myself with the FactHandle, as I plan to leave them in working
memory and change values on those 3 objects from the main application in each
application loop, then make decisions in the rule engine based on the values of
those 3 objects.   However, for now I just nee to find out why the
objects only live for my first loop and call of session.fireAllRules().
 
Any ideas or what I am doing wrong?
 
Thanks,

Chris


      
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