[drools-user] getQueryResults always returns null in drools 3.0.4

[Geoffrey De Smet]

I have a query like this in my drl file:

query "multipleLessonsPerTeacherPerTimeslot"
    $lesson : Lesson($id : id, $teacher : teacher,
                     $timeslot : timeslot);
    exists Lesson(id > $id, teacher == $teacher,
                  timeslot == $timeslot);
end


But when I do this in my java code
  workingMemory.fireAllRules();
  workingMemory.getQueryResults("multipleLessonsPerTeacherPerTimeslot");
the second line returns null, there are no QueryResults.


Even when I change the query to something simple this:
  query "multipleLessonsPerTeacherPerTimeslot"
    lesson : Lesson()
  end
it still returns null.


But if I try this with a rule, like this:
  rule teacherCanOnlyTeachOneGroupAtATime
  when
    $lesson : Lesson($id : id, $teacher : teacher,
                     $timeslot : timeslot);
    exists Lesson(id > $id, teacher == $teacher,
                  timeslot == $timeslot);
  then
    assertLogical(new HardConstraint(1));
  end
together with this java code:
  workingMemory.fireAllRules();
  workingMemory.getObjects(HardConstraint.class);
it does not return null, but a correct list.


Any idea what I am doing wrong? Thanks for any help.

--
With kind regards,
Geoffrey De Smet


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