I've one .DRL file which has say 10 rules. Once I insert a fact, some rules may be matched- how do I find out which rules were matched programmatically?
Note that this answer is valid for versions of Drools up to 5.x. If you have moved on to 6 or above, then take a look at the modified answer from @melchoir55. I haven't tested it myself, but I'll trust that it works.
To keep track of rule activations, you can use an AgendaEventListener. Below is an example, as found here:
You just need to create such a listener and attach it to the session like so:
ksession = kbase.newStatefulKnowledgeSession();
AgendaEventListener agendaEventListener = new TrackingAgendaEventListener();
ksession.addEventListener(agendaEventListener);
//...
ksession.fireAllRules();
//...
List<Activation> activations = agendaEventListener.getActivationList();
Note that there is also WorkingMemoryEventListener which enables you to do the same with tracking insertions, updates and retractions of facts.
Code for a tracking & logging AgendaEventListener:
package com.sctrcd.drools.util;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import org.drools.definition.rule.Rule;
import org.drools.event.rule.DefaultAgendaEventListener;
import org.drools.event.rule.AfterActivationFiredEvent;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* A listener that will track all rule firings in a session.
*
* @author Stephen Masters
*/
public class TrackingAgendaEventListener extends DefaultAgendaEventListener {
private static Logger log = LoggerFactory.getLogger(TrackingAgendaEventListener.class);
private List<Activation> activationList = new ArrayList<Activation>();
@Override
public void afterActivationFired(AfterActivationFiredEvent event) {
Rule rule = event.getActivation().getRule();
String ruleName = rule.getName();
Map<String, Object> ruleMetaDataMap = rule.getMetaData();
activationList.add(new Activation(ruleName));
StringBuilder sb = new StringBuilder("Rule fired: " + ruleName);
if (ruleMetaDataMap.size() > 0) {
sb.append("\n With [" + ruleMetaDataMap.size() + "] meta-data:");
for (String key : ruleMetaDataMap.keySet()) {
sb.append("\n key=" + key + ", value="
+ ruleMetaDataMap.get(key));
}
}
log.debug(sb.toString());
}
public boolean isRuleFired(String ruleName) {
for (Activation a : activationList) {
if (a.getRuleName().equals(ruleName)) {
return true;
}
}
return false;
}
public void reset() {
activationList.clear();
}
public final List<Activation> getActivationList() {
return activationList;
}
public String activationsToString() {
if (activationList.size() == 0) {
return "No activations occurred.";
} else {
StringBuilder sb = new StringBuilder("Activations: ");
for (Activation activation : activationList) {
sb.append("\n rule: ").append(activation.getRuleName());
}
return sb.toString();
}
}
}