New subject: Multiple Object Referencing problem

Tuesday, 8 June 2010

Hi Esteban,

I am getting the error at a place where I am trying to write back from my working memory
to my output file.
It is happening because the second rule to turn on the sprinkler does not work and as a
result a null value is getting stored.
Is it possible that there can exists 2 different Room() objects with the same room.name
??
Because the room objects are getting stored from different files to the working memory ??
Do you think it better to store room objects in a separate list??
I store all information into a list and load that into the memory.
Am I going wrong here?

Please help.

Thank you.
-M
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Today's Topics:

   1. Re: Multiple Object Referencing problem (Esteban Aliverti)
   2. Re: Exception using persistence (Alan.Gairey(a)tessella.com)

----------------------------------------------------------------------

Message: 1
Date: Tue, 8 Jun 2010 09:25:47 -0300
From: Esteban Aliverti <esteban.aliverti(a)gmail.com&gt;
Subject: Re: [rules-users] Multiple Object Referencing problem
To: Rules Users List <rules-users(a)lists.jboss.org&gt;
Message-ID:
        <AANLkTilCFcZwhX6uthWz3tIvkJXdtqVKXcb0uG-rqm91(a)mail.gmail.com&gt;
Content-Type: text/plain; charset="windows-1252"

Look at the line 58 of RulesTest class and you will find the problem. Try to
always analyse the stacktrace if there are no drools classes involved, then
it is not a Drools error. And remember, the debugger is your friend ;)

Best,

2010/6/7 David Sinclair <dsinclair(a)chariotsolutions.com&gt;

...
 This has nothing to do with Drools. It looks like you are giving
Writer bad
 input perhaps??

 Exception in thread "main" *java.lang.NullPointerException*

       at java.io.Writer.write(Unknown Source)

       at com.org.RulesTest.main(*RulesTest.java:58*)

 2010/6/7 Fnu Mahalakshmi <FMahalakshmi(a)nyx.com&gt;

>  Hi,
>
>
>
> I am trying out this example from the book :
>
> public class Room {
>
>     private String name
>
>     // getter and setter methods here
>
> }
>
> public classs Sprinkler {
>
>     private Room room;
>
>     private boolean on;
>
>     // getter and setter methods here
>
> }
>
> public class Fire {
>
>     private Room room;
>
>     // getter and setter methods here
>
> }
>
>
>
> I load 2 input files: 1. with data of fire and Room { f1, r1;f2, r2}
>
>                            2. with data of sprinkler and Room { ? ?, r1; ?
> ? , r2}
>
>
>
> I am writing rule ? if fire exists in room start sprinkler? { so if f1 and
> r1 in this case: I should get s1, r1 }
>
> when
>
>     Fire($room : room)
>
>     $sprinkler : Sprinkler( room == $room, modified == false )
>
> Then
>
>     $sprinkler.setmodified(true);
>
>     modify( $sprinkler ) { setSprinkle( ?s1? ) };
>
> end
>
>
>
> But this gives me error:
>
> Exception in thread "main" *java.lang.NullPointerException*
>
>       at java.io.Writer.write(Unknown Source)
>
>       at com.org.RulesTest.main(*RulesTest.java:58*)
>
>
>
> From what I observed this rule is not getting fired at all.
>
> I want this rule to be fired on the data in my second input file.
>
> The rules for my first input file get executed properly.
>
>
>
> Can any1 tell me where I am going wrong??
>
> Is there any way in which we can use the modified data { after rules are
> fired on the first input data and it is  modified}to fire another set of
> rules on the same input depending on the next input file???
>
>
>
> Thank you.
>
>
>
> -M
>
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Re: [rules-users] Multiple Object Referencing problem