如何在Drools规则中声明列表

Question

I've got a simple object construction. The class ContextDroolsObject has a property of type Map called objects . Inside that map there's a key "imageThemes" with an ArrayList and this rule here never matches:

import java.util.ArrayList;
import java.util.Map;
import com.my.ContextDroolsObject;

dialect 'java'


rule 'Soccer Image Theme'
    salience 100
    when
        s : ContextDroolsObject()
        objectsm : Map() from s.objects
         imageThemesList : ArrayList() from outputsm.imageThemes
    then
System.out.println("-----------------------soccer");
    end

I've also tried with List() with same result.

¿How to match the list declaration?

Answer 1

Hi you can rewrite your rule in this way:

import java.util.ArrayList;
import java.util.Map;
import com.my.ContextDroolsObject;

dialect 'java'


rule 'Soccer Image Theme'
salience 100
when
    s : ContextDroolsObject( imageThemesList : objects#Map.get("imageThemes") )
then
    System.out.println("-----------------------soccer");
end

Answer 2

Using a hierarchical structure for fact objects is ver frequently a design flaw. You may not be able to reason conveniently over the list elements.

Anyway, this is the way to extract the list within the map from the ContextDroolsObject.

rule 'Soccer Image Theme'
  salience 100
when
  s: ContextDroolsObject() 
  imageThemesList: ArrayList() from s.getObjects().get( "imageThemes" )
then
  System.out.println("-----------------------soccer");
end