Drool takes the updated rule - spring

Question

I would like to keep business logic separate from web application (spring MVC + Hibernate) for better maintainability and I do not want to restart the server for the business logic change. If I modify DRL file for business change, would the drool engine pick the latest DRL?
I did a test application, but the updated DRL file is not loaded into 'KnowledgeBase'. Is there any way to load the updated DRL/rules in Drools engine without restart the server?
Account.java
public class Account {
private Integer balance;
// setter & getter
}
And the test program has :
KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();
kbuilder.add(ResourceFactory.newClassPathResource("myrule.drl"), ResourceType.DRL);
KnowledgeBase kbase = kbuilder.newKnowledgeBase();
StatelessKnowledgeSession ksession = kbase.newStatelessKnowledgeSession();
Account account = new Account(1000);
account.withdraw(500);
ksession.execute(account);
And DRL is
rule "belowLimit"
when
$account : Account( balance < 700 )
then
System.out.println("Notify user");
end

Answer 1

Drools 5.x versions (as you are apparently using) featured Change Sets which define directories or files to be watched for changes so that the Knowledge Base would be rebuilt automatically and sessions started thereafter might reflect the new Knowledge Base.
Detaiks can be found in the documentation see section" Knowledge Base by Configuration Using Changesets" and its successor. It's really too much to repeat it all here.

Answer 2

6.x now makes this much simpler. It's based around maven versioning. A KieContainer (contains the runtime bits) can be started agains any version of a jar. You can then update it to any version of a jar too, using the method updateToVersion. Finally kie-ci provides embedded maven support for automatic updates, and resolutions from external maven repositories, using maven version update standards.
http://docs.jboss.org/drools/release/6.0.0.Final/drools-docs/html/KIEChapter.html#BuildDeployUtilizeAndRunSection

Answer 3

You have to use KieScanner to achieve this. Here is a quote from the documentation:
The KieScanner allows continuous monitoring of your Maven repository
to check whether a new release of a Kie project has been installed. A
new release is deployed in the KieContainer wrapping that project. The
use of the KieScanner requires kie-ci.jar to be on the classpath.
KieServices kieServices = KieServices.Factory.get();
ReleaseId releaseId = kieServices.newReleaseId( "org.acme", "myartifact", "LATEST" );
KieContainer kContainer = kieServices.newKieContainer( releaseId );
KieScanner kScanner = kieServices.newKieScanner( kContainer );
// Start the KieScanner polling the Maven repository every 10 seconds
kScanner.start( 10000L );
You also can use ks.scanNow().
Remember to build your project with incremental version checked, as drools will check whether any new version of that artifact is present or not. If yes, then it will only swap in runtime.