[rules-users] How can generated facts/events be published?

[Edson Tirelli]

   Try:

// this is type of control fact
declare MsgSent
    msg : StatusMessage
end

rule publish
when
    $msg : StatusMessage( )
    not MsgSent( msg == $msg )
then
    // publish
    insert( new MsgSent( $msg ) ); // using 5.1.1, otherwise needs to use
empty constructor and set the field
end

rule cleanup
when
    $snt : MsgSent( )
    not StatusMessage( this == $snt.msg )
then
    retract( $snt );
end

   Edson

2010/8/29 Tina Vießmann <tviessmann at stud.hs-bremen.de>

>  Thank you, Wolfgang! :)
>
> Let's say:
> I'm generating StatusMessage objects during the rule processing. They will
> be published. But they are also need for further processing (so they can not
> be deleted after publishing).
> The StatusMessage objects defined as simple POJOs.
>
> If I'm publishing the StatusMessage objects using a rule like
>     rule 'publish StatusMessages'
>         when
>             $msg : StatusMessage( )
>         then
>             // publish
>     end
> In this case every StatusMessage would be send again and again.
> My first impression for a solution would be to define a Boolean field
> 'send' that signals if the object has been send. But the field would just be
> needed for Drools internal processing. So I thought of defining this
> additional field using the declare statement. But if I remember correctly
> from previous tries, such a things are not possible because the declare
> statement with the additional field is the definition of a new type... Am I
> right so far?
>
> Do you have a idea how I can solve my problem of sending an fact/event just
> once but keep it in the memory for further processing?
>
> Thank sou!
> Tina
>
>
>
> The usual method:
> You establish a TopicPublisher as a global declared in your .drl file.
>    global TopicPublisher topicPublisher
> You must set this from Java code using
>    TopicPublisher topicPublisher = ...;
>    statefulKnowledgeSession.setGlobal( "publisher", topicPublisher )
> and then you use it in any RHS code.
>
> Of course, a TopicPublisher could also be (field of) some fact,
> but this shouldn't be necessary for such a central service.
>
> -W
>
>
> On 29 August 2010 19:16, Tina Vießmann <tviessmann at stud.hs-bremen.de>wrote:
>
>>  Hi,
>>
>> I've got a simple question.
>>
>> How can I get generated facts out of the memory (for publishing them
>> using JMS)?
>>
>> Thanks :)
>> Tina
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>>
>
>
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-- 
  Edson Tirelli
  JBoss Drools Core Development
  JBoss by Red Hat @ www.jboss.com
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