KieSession 除了提供豐富的API外, 還提供三個(gè)event listener, 方便對(duì)于規(guī)則執(zhí)行狀況的監(jiān)控.

AgendaEventListener

該接口可以監(jiān)控 rule 被fire, 所以這個(gè)listener最常用, 對(duì)于規(guī)則的計(jì)算, 我們很可能需要做logging, 常見的做法是在drl的RHS主動(dòng)做logging, 但這并不是很好的方式, 一來RHS代碼會(huì)變得冗長(zhǎng), 二來也可能會(huì)漏寫logging.
使用方法:
Drools 提供了一個(gè)缺省的 DefaultAgendaEventListener 類, 我們可以實(shí)例化一個(gè)這個(gè)類, 并重載一些我們關(guān)注的方法, beforeMatchFired() 方法是在規(guī)則執(zhí)行之前被調(diào)用;afterMatchFired() 方法是在規(guī)則執(zhí)行之后被調(diào)用; matchCreated() 方法是規(guī)則被放到agenda時(shí)被調(diào)用;

RuleRuntimeEventListener

可以監(jiān)聽哪些fact 被加到working memory中了, 不管這些fact是通過rule還是java端做的insert()/update()/delete() 都能觸發(fā) RuleRuntimeEventListener.
使用方法:
Drools 提供了一個(gè)缺省的 DefaultRuleRuntimeEventListener 類, 我們可以實(shí)例化一個(gè)這個(gè)類.

ProcessEventListener

這個(gè)監(jiān)聽的事件僅和jBPM相關(guān), 所以不需要關(guān)心.

示例代碼

• drl 規(guī)則文件:

package com.sample.rules
 
import com.sample.Order;

 
rule "not_worry_loop"
   when
       $order:Order(originalPrice>0)
   then
      $order.setAmount(100);
      update($order) ; //trigger DefaultRuleRuntimeEventListener  
end   

• java 測(cè)試文件:

package com.sample;

import java.util.List;

import org.drools.core.event.DefaultAgendaEventListener;
import org.junit.Test;
import org.kie.api.KieServices;
import org.kie.api.event.rule.AfterMatchFiredEvent;
import org.kie.api.event.rule.DefaultRuleRuntimeEventListener;
import org.kie.api.event.rule.ObjectDeletedEvent;
import org.kie.api.event.rule.ObjectUpdatedEvent;
import org.kie.api.runtime.KieContainer;
import org.kie.api.runtime.KieSession;

public class UnitTest {

	@Test
	public void test() {

		// load up the knowledge base
		KieServices ks = KieServices.Factory.get();
		KieContainer kContainer = ks.getKieClasspathContainer();
		KieSession kSession = kContainer.newKieSession("ksession-rules");

		kSession.addEventListener(new DefaultAgendaEventListener() {
			@Override
			public void afterMatchFired(AfterMatchFiredEvent event) {
				// TODO Auto-generated method stub
				super.afterMatchFired(event);
				System.out.println("=============");
				List<Object> orders = event.getMatch().getObjects();
				for (Object order : orders) {
					System.out.println(order);
				}
			}
            @Override
            public void matchCreated(MatchCreatedEvent event) {
				super.matchCreated(event);
                System.out.println("The rule " + event.getMatch().getRule().getName() + " can be fired in agenda");
            } 

            @Override
            public void matchCancelled(MatchCancelledEvent event) {
				super.matchCancelled(event);
                System.out.println("The rule " + event.getMatch().getRule().getName()+ " cannot b in agenda");
           }			
		});

		kSession.addEventListener(new DefaultRuleRuntimeEventListener() {
			@Override
			public void objectDeleted(ObjectDeletedEvent event) {
				// TODO Auto-generated method stub
				super.objectDeleted(event);
				System.out.println("deleted:" + event.getOldObject());
			}

			@Override
			public void objectInserted(ObjectInsertedEvent event) {
				// TODO Auto-generated method stub
				super.objectInserted(event);
				System.out.println("inserted:" + event.getObject());
			}			

			@Override
			public void objectUpdated(ObjectUpdatedEvent event) {
				// TODO Auto-generated method stub
				super.objectUpdated(event);
				System.out.println("update:" + event.getObject());
			}
		});

		Order order = null;
		order = new Order();
		order.setAmount(2);
		order.setOriginalPrice(0.2D);
		kSession.insert(order);

		order = new Order();
		order.setAmount(20);
		order.setOriginalPrice(2.0D);
		kSession.insert(order);
		kSession.fireAllRules();

		kSession.dispose();

	}
}