Drools 7 access fact in DRL file

Question

I'm passing a string into a drools rule with Drools 7:

public static void main(String[] args) {
    log("Starting");

    KieContainer kc = KieServices.Factory.get().getKieClasspathContainer();
    KieSession ksession = kc.newKieSession("RulesKS");
    ksession.insert( "asdf" );
    ksession.fireAllRules();

    ksession.dispose();
    log("Done");
}

Note that I'm setting a "fact" with a value of asdf to run the rule against. Here is my rule file:

package drools7

function boolean ifContains(String target, String searchFor) {
    return target.indexOf(searchFor) != -1;
}

rule "First Rule"
    salience 90
    when
        eval(ifContains("target", "et"))
    then
        System.out.println("Does contain");
end

Now, when I run my main method I see:

Does contain

printed to stdout, but how would I check in the drools rule file the actual fact that I inserted?

How does this work? I want to see if the fact contains "et", not a scalar value?

score 1 · Accepted Answer · answered Mar 02 '18 at 14:08

I would recommend you to read Drools official documentation and/or some Drools book first.

For your particular case, what you need to do is to write a pattern that matches your fact in the left hand side of the rule:

rule "First Rule"
  salience 90
  when
    String(ifContains(this, "et"))
  then
    System.out.println("Does contain");
end

You can even optimize your rule to avoid using an unnecessary function definition and call by using the contains operator:

rule "First Rule"
  salience 90
  when
    String(this contains "et")
  then
    System.out.println("Does contain");
end

Hope it helps,

Drools 7 access fact in DRL file

1 Answers1