[rules-users] How to catch Exceptions when firing rules

[Anstis, Michael (M.)]

For what it's worth I think this would be a good idea too.
 
Perhaps the default ASM wrapper around the RHS could use a try...catch
block and log any exceptions of a rules' activation in a (drools)
accessible log? Heck you could even allow certain accepted exceptions to
be defined as a property of the rule; and any other non-defined
exception types cause the session to become invalidated. If we're ever
to let "the business" define rules we need to accept they might make
mistakes that we're better off capturing and report back than invalidate
the whole session. Why should a whole session be invalidated because a
single rule activation failed anyway?
 
With kind regards,
 
Mike 


________________________________

	From: rules-users-bounces at lists.jboss.org
[mailto:rules-users-bounces at lists.jboss.org] On Behalf Of Yang Song
	Sent: 24 August 2007 16:16
	To: Rules Users List
	Subject: Re: [rules-users] How to catch Exceptions when firing
rules
	
	
	Thanks a lot for the answer, Mark. But I don't think it makes
sense. 
	 
	Because in some scenarios, you cannot guarantee the consequence
part of rule is 100% correct -- there could be errors happening in
run-time which are hard to predict, especially when a complex action or
logic will be executed as the concequece. 
	 
	There should at least be some mechanisms to tell whoever fires
the rule that there is something wrong during the rule firing process,
then and he can do something, e.g. create a new session. Also it should
enable the rule firer to catch these exceptions and do the clean up work
silently -- instead of leaving these things on the stderr even cannot be
seen in the logs. This will make the program depending on the JBoss
Rules to be more robust. 
	 
	What do you think? If JBoss Rules already has the ability to do
this job, can you please let me know?
	 
	Thanks again,
	Yang
	
	 
	On 8/24/07, Mark Proctor <mproctor at codehaus.org> wrote: 

		Once an exception is thrown on a conseuqence the current
session is considered invalid. You'll need to add the try catch inside
of the actual consequence.
		
		Mark
		Yang Song wrote: 

			
			Hi, 
			 
			Anyone knows how to catch the exception when
firing the rules? 
			 
			I wrapped the session.fireAllRules() method
using try...catch, however it doesn't work: when someone wrote bad code
in the rule's action part, the Exception will be thrown and printed to
the stderr, and this will make the rule engine stop working -- the
try...catch outside doesn't help anything. 
			 
			If  the exception thrown from the rule's action
part can be caught externally, the system can be protected from
interrupting Exception.

			try {
			        _log.debug("Firing rules in : " +
getName());

			        session.fireAllRules();

			} catch (Exception e) {
			        _log.info("Error when firing rules: ",
e);
			} 
			

			Thanks, 
			Yang

			
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