I have a function that returns Optional that I want to use in drools eval, e.g.
rule "some rule"
when
eval(func().orElse(1.0) > 0.0)
then
....
end
where func() has return type being Optional<Double>. The above is giving me compile error because of orElse. Is there any workaround? Thanks!
Avoid using eval.
Assign the function call's result to a Double and do the comparison there. Something like...
Double( this > 0.0 ) from func().orElse(1.0)
Drools support for Java built-ins and newer functionality (Java 8+) has been hit-or-miss in DRL in my experience, especially with older Drools. If this all doesn't work, your best bet might be to write a method that will wrap the func().orElse(...) and resolve to a simple Double and use that instead.