24.6. Pet Store Example: Putting Items Into Working Memory from PetStore.drl

// Insert each item in the shopping cart into the Working Memory 
rule "Explode Cart"
    agenda-group "init"
    auto-focus true
    salience 10
    dialect "java"
when
    $order : Order( grossTotal == -1 )
    $item : Purchase() from $order.items
then
    insert( $item );
    kcontext.getKnowledgeRuntime().getAgenda().getAgendaGroup( "show items" ).setFocus();
    kcontext.getKnowledgeRuntime().getAgenda().getAgendaGroup( "evaluate" ).setFocus();
end
  • The first extract fires first because it has the auto-focus attribute set to true.
  • This rule matches against all orders that do not yet have their grossTotal calculated . It loops for each purchase item in that order. Some parts of the "Explode Cart" rule should be familiar: the rule name, the salience (suggesting the order for the rules being fired) and the dialect set to java.
  • agenda-group init defines the name of the agenda group. In this case, there is only one rule in the group. However, neither the Java code nor a rule consequence sets the focus to this group, and therefore it relies on the next attribute for its chance to fire.
  • auto-focus true ensures that this rule, while being the only rule in the agenda group, can fire when fireAllRules() is called from the Java code.
  • kcontext....setFocus() sets the focus to the show items and evaluate agenda groups in turn, permitting their rules to fire. In practice, you can loop through all items on the order, inserting them into memory, then firing the other rules after each insert.
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