defining rules engine listener

You can listen to rules engine execution events through the RulesEngineListener API:

/**
 * A listener for rules engine execution events.
 *
 * @author Mahmoud Ben Hassine ([email protected])
 */
public interface RulesEngineListener {

    /**
     * Triggered before evaluating the rule set.
     * <strong>When this listener is used with a {@link InferenceRulesEngine}, this method will be triggered before the evaluation of each candidate rule set in each iteration.</strong>
     *
     * @param rules to fire
     * @param facts present before firing rules
     */
    void beforeEvaluate(Rules rules, Facts facts);

    /**
     * Triggered after executing the rule set
     * <strong>When this listener is used with a {@link InferenceRulesEngine}, this method will be triggered after the execution of each candidate rule set in each iteration.</strong>
     *
     * @param rules fired
     * @param facts present after firing rules
     */
    void afterExecute(Rules rules, Facts facts);
}

You can implement this interface to provide custom behavior to execute before/after firing the whole rule set. To register your listener, use the following snippet:

DefaultRulesEngine rulesEngine = new DefaultRulesEngine();
rulesEngine.registerRulesEngineListener(myRulesEngineListener);

You can register as many listeners as you want, they will be executed in their registration order.