I’m trying to make a simple implementation of RuleBook engine with the follwing class:

package some package;

import com.deliveredtechnologies.rulebook.FactMap;
import com.deliveredtechnologies.rulebook.NameValueReferableMap;
import com.deliveredtechnologies.rulebook.annotation.Given;
import com.deliveredtechnologies.rulebook.annotation.Rule;
import com.deliveredtechnologies.rulebook.annotation.Then;
import com.deliveredtechnologies.rulebook.annotation.When;
import com.deliveredtechnologies.rulebook.model.runner.RuleBookRunner;
import java.util.Random;

public class RuleBookMain {

  private static final int RANGE = 10;
  private static boolean numberGuessed;

  public static void main(String[] args) {
    Player p1 = new Player("Andrew");
    Player p2 = new Player("Anna");

    Guess startingGuess = new Guess(p1);

    RuleBookRunner ruleBookRunner = new RuleBookRunner("some package");

    NameValueReferableMap<Object> facts = new FactMap<>();
    facts.setValue("p1", p1);
    facts.setValue("p2", p2);
    facts.setValue("guess", startingGuess);

    while (!numberGuessed) {
      System.out.println("Facts before running rules: " + facts);
      ruleBookRunner.run(facts);
    }
  }

  @Rule(order = 1)
  public static class NumberGuessedRule {
    @Given("p1")
    private Player p1;
    @Given("p2")
    private Player p2;
    @Given("guess")
    private Guess guess;

    @When
    public boolean when() {
      System.out.println("NumberGuessedRule.when: p1=" + p1 + ", p2=" + p2 + ", guess=" + guess);
      boolean result = (guess.number == p1.secret && !guess.author.equals(p1))
                       ||
                       (guess.number == p2.secret && !guess.author.equals(p2));
      System.out.println("NumberGuessedRule.when: result=" + result);
      return result;
    }

    @Then
    public void then(FactMap<Object> facts) {
      // Add debug statements to check for null values
      System.out.println("NumberGuessedRule.then: p1=" + p1 + ", p2=" + p2 + ", guess=" + guess);
      Player guessedPlayer = guess.number == p1.secret ? p1 : p2;
      System.out.println("Number guessed! " + guessedPlayer + " is leaving the game.");
      numberGuessed = true;
    }
  }

  @Rule(order = 2)
  public static class WrongGuessRule {

    @Given("p1")
    private Player p1;
    @Given("p2")
    private Player p2;
    @Given("guess")
    private Guess guess;

    @When
    public boolean when() {
      return (guess.number != p1.secret && !guess.author.equals(p1))
             ||
             (guess.number != p2.secret && !guess.author.equals(p2));
    }

    @Then
    public void then(FactMap<Object> facts) {
      Player guessingPlayer = guess.number != p1.secret ? p1 : p2;
      Guess newGuess = new Guess(guessingPlayer);
      facts.setValue("guess", newGuess);
      System.out.println(newGuess);
    }
  }


  private static int randomNumber() {
    return new Random().nextInt(RANGE);
  }



  static class Guess {

    public Player author;
    public int number;

    public Guess(Player author) {
      this.author = author;
      this.number = randomNumber();
    }

    @Override
    public String toString() {
      return author + " says '" + number + "'";
    }
  }




  static class Player {

    public int secret;
    public String name;

    public Player(String name) {
      this.name = name;
      this.secret = randomNumber();
    }

    @Override
    public String toString() {
      return name + " (secret=" + secret + ")";
    }
  }

}

When I run main I receive the following error:

11:44:34.099 [main] ERROR com.deliveredtechnologies.rulebook.model.GoldenRule -- Error invoking action on class com.deliveredtechnologies.rulebook.model.runner.RuleAdapter$$Lambda$120/0x000001f8110823e8
java.lang.reflect.InvocationTargetException: null
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    at com.deliveredtechnologies.rulebook.model.GoldenRule.lambda$invoke$8(GoldenRule.java:176)
    at java.base/java.util.Optional.ifPresent(Optional.java:178)

Caused by: java.lang.IllegalArgumentException: null

Nothing worked at all!