Questions concerning JBoss-Rules (JBR)
A few disclaimers first:
- "JBoss" is copyrighted, trademarked and other legally restrictive things...
- I'm not employed by JBoss and I do not offer certified JBoss consultancy.
What's the difference between insert
and assert?
Up to JBR 4.03 the keyword to add facts to
workingMemory was assert. It has been
renamed to insert in release 4.03.
How do I get facts back from WorkingMemory?
You called
workingMemory.fireAllRules(), and now you
want your facts (aka: your business objects) back.
Quite understandable, but don't worry: You never lost
them to working memory. Clever as many JBR features,
working memory only keeps references to the facts you
asserted or inserted. You can safely continue with your
normal stuff and use your objects (facts) as
if nothing happened.
But: Rules might have created new facts, which your
business code might need to know about. In such cases
you can query working memory to return an
Iterator or QueryResults of
facts. It then remains as a programming exercise to
retrieve the ones your interested in... Look at the
WorkingMemory API for further info.
Does JBR recognize when my business objects (facts) are modified?
Yes or no, depending on how you added the facts to
working memory. In prior versions of JBR or Drools, one
had to call a 'modify' method to inform the engine
about changes. Nowadays you tell JBR to add a
PropertyChangeListener to your facts upon
'insert/assert'.
How to I trace which rules fire?
Add a DebugEventListenerto your
RuleBase or your WorkingMemory. Be warned, though. Such
listeners might create loads of output. It differs from
the normal stacktrace, as the precious line you really
need will unlikely be the topmost one...
Add the following line to your code (where
session is your workingMemory).
session.addEventListener(new DebugAgendaEventListener());