[rules-users] Query in stateless knowledge session returns no results

[Heijink, Hank]

Aha! I missed the line about the dispose. That makes a lot of sense. What I don't understand is why the example 3.37 in the docs would work. If I understand what you're saying, it shouldn't.

Thanks!
Hank

Sent from my iPhone

On Jul 30, 2011, at 8:27 AM, "Wolfgang Laun" <wolfgang.laun at gmail.com<mailto:wolfgang.laun at gmail.com>> wrote:

StatelessKnowledgeSession.execute(...) executes the command(s) and finally calls dispose() on the session. Use a stateful session or a global (filled with a low-salience rule) or  -  simply use the getObjects command.
-W

On 29 July 2011 22:47, Heijink, Hank <<mailto:heijink at audible.com>heijink at audible.com<mailto:heijink at audible.com>> wrote:
Hi all,

I'm new to Drools, so please excuse me if I'm asking about the obvious--it's certainly not obvious to me. The problem is this: I use a stateless knowledge session where a list of facts is inserted. The rules that fire create new facts, and after all the rules have fired, I'd like to obtain a list of all the facts (the old and the new). The best way seemed to use a query. I'm using Drools 5.1 on Linux.
This is part of my .drl file (without the imports):

rule "create badge"
when
       Event ( eventType == EventType.SOME_EVENT_TYPE )
       not BadgeState ( identifier == "badge" )
then
       insert( new BadgeState("badge") );
end

query "all badges"
       aBadge : BadgeState()
end

This is the Java code:

               StatelessKnowledgeSession ksession = StatsKnowledgeBase.getKnowledgeBase().newStatelessKnowledgeSession();

               // Create a list of share events
               ArrayList<Event> events = new ArrayList<Event>();
               Date now = new Date();
               MobileDevice aDevice = new MobileDevice("uniqueId", "deviceType");
               for (int i = 0; i < 5; i++) {
                       Event anEvent = new Event.Builder(now, aDevice, "aCustomer", EventType.SOME_EVENT_TYPE).build();
                       events.add(anEvent);
               }

               // Create the query for the badges
               List<Command> commands = new ArrayList<Command>();
               commands.add(CommandFactory.newInsertElements(events));
           commands.add(CommandFactory.newQuery("all badges", "all badges"));

               // Feed the events into Drools
               KnowledgeRuntimeLogger logger = KnowledgeRuntimeLoggerFactory.newConsoleLogger(ksession);
               ExecutionResults results = ksession.execute( CommandFactory.newBatchExecution(commands) );
               NativeQueryResults queryResults = (NativeQueryResults)results.getValue("all badges");

// At this point, queryResults is empty.

               logger.close();

               // Get a list of badges
               List<BadgeState> badges = new ArrayList<BadgeState>();
               for (Iterator<QueryResultsRow> i = queryResults.iterator(); i.hasNext(); ) {
                       QueryResultsRow result = i.next();
                       BadgeState obj = (BadgeState)result.get("aBadge");
                       badges.add(obj);
               }

The logger shows me that the BadgeState object is created, but the query returns an empty list. I've searched the documentation, which suggests that I'm doing it right (<http://drools.herod.net/drools-expert/html/ch03.html#d0e1956>http://drools.herod.net/drools-expert/html/ch03.html#d0e1956, example 3.37), the archives of this mailinglist, and the web, so far without success.

Clearly, I'm missing something, and I have the nagging feeling that it's something simple...

Any help is much appreciated!

Best,
Hank


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