Since you ask me... It may not be "wisdom", though...

I do not use 'dialect "mvel"' in the rules I write. Here are some facts on which this decision is based.
There's some good reasons why MVEL has been introduced into Drools, and why it is used when and where it is used. But I wouldn't recommend it's use in RHS of rules just to save me the trouble of writing the more verbose Java equivalent.

Also, I'd like to point out that MVEL bug fixing has picked up as soon as Drools team members were available to do so. 

Cheers
Wolfgang


2012/3/10 Zhuo Li <milanello1998@gmail.com>

Yep, Wolfgang,

 

It’s a code issue – I just identified it… thanks. I have another thread talking about NoClassDefFound exception. Would appreciate if you can share your wisdom there.

 

Best

Abe

 

发件人: rules-users-bounces@lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] 代表 Wolfgang Laun
发送时间: 2012年3月11日 1:06
收件人: Rules Users List
主题: Re: [rules-users] Adhoc NullPointer exception in rule execution

 

The location of the NPE is 

    at com.xxx.xxx.xxx.xxx.xxx.xxx.xxx(xxx.java:634)

and that's your code, invoked from the right hand side of rule Match.

 

-W

 

2012/3/10 Zhuo Li <milanello1998@gmail.com>

Hi, folks,

 

I’m using Drools 5.1, MVEL dialect, JDK 1.6 to build a OLTP system running on tomcat 6.0.28. the runtime environment is on a cloud virtual and node profile is relatively small. We’ve noticed below run time exceptions from prod since it’s online from day one which is impacting transaction processing. However it is happening adhoc-ly. Here I have 1 question:

 

1.       The yellow marked lines are actually java file compiled from DRL file. Why there is null pointer exception thrown from org.drools.common.DefaultAgenda.fireActivation?

 

ERROR>2012-02-25 11:42:25,071 com.xxx.xxx.xxx.xxx[DefaultQuartzScheduler_Worker-3]: Rules run time error:

org.drools.runtime.rule.ConsequenceException: rule: Match

 

        at org.drools.runtime.rule.impl.DefaultConsequenceExceptionHandler.handleException(DefaultConsequenceExceptionHandler.java:39)

        at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:916)

        at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:845)

        at org.drools.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1056)

        at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:733)

        at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:699)

        at org.drools.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:218)

        at com. xxx.xxx.xxx.xxx.xxx.xxx.xxx (SessionManager.java:94)

        at com. xxx.xxx.xxx.xxx.xxx.xxx.yyy(SessionManagerJob.java:17)

        at org.quartz.core.JobRunShell.run(JobRunShell.java:202)

        at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:525)

Caused by: java.lang.NullPointerException

        at com.xxx.xxx.xxx.xxx.xxx.xxx.xxx(xxx.java:634)

        at com.xxx.xxx.xxx.xxx.xxx.yyy.yyy(yyy.java:227)

        at com.xxx.xxx.xxx.xxx.xxx.yyy.zzz(zzz.java:115)

        at com.xxx.xxx.xxx.xxx.xxx.yyy.ttt(ttt.java:83)

        at com.xxx.xxx.xxx.xxx.xxx.yyy.uuu(uuu.java:75)

        at com. com.xxx.xxx.xxx.xxx.xxx.yyy.vvv(vvv.java:9)

        at com. com.xxx.xxx.xxx.xxx.xxx.yyy.www(www.java:28)

        at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:906)

        ... 9 more

Best regards

Abe


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