Here is a method cut & pasted from working code in a validation class used by some of my unit tests. I think it does what you are asking.

                private ValidationResult addDrlToKnowledgeBase(String drlAsString )

                {

                                ValidationResult retval = null;

                                try

                                {

                                                KnowledgeBuilder kBuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();

                                                Reader rdr = new StringReader(drlAsString);

                                                Resource resource = ResourceFactory.newReaderResource(rdr);

                                                kBuilder.add(resource, ResourceType.DRL);

                                                if (kBuilder.hasErrors())

                                                {

                                                                retval = ValidationResult.newInstance("DRL errors: " + kBuilder.getErrors().toString(), null, null);

                                                }

                                                else

                                                {

                                                                knowledgeSession.getKnowledgeBase().addKnowledgePackages(kBuilder.getKnowledgePackages());

                                                                retval = ValidationResult.newInstance();

                                                }

                                }

                                catch(Exception ex)

                                {

                                                retval = ValidationResult.newInstance(ex.getMessage(), null, ex);

                                }

                                return retval;

                }

The type of the instance variable “knowledgeSession” is “StatefulKnowledgeSession”. Ignore the class “ValidationResult”, it is a custom class used for returning results from this validation helper class. Hope this helps.

-Nathan Bell

From: rules-users-bounces@lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Pierre de Leusse
Sent: Thursday, November 18, 2010 8:14 AM
To: 'Rules Users List'
Subject: [rules-users] Programatically adding rules toKnowledgeBase/StatefulKnowledgeSession

Hello all,

I’m trying to add rules through my java code to a KnowledgeBase and I cannot find any easy way to do so. So far, the only solution I could think of, is to write the rule as DRL in a file that is “observed” by a KnowledgeAgent (same with a RuleAgent I suppose). Is it possible to create a new KnowledgePackage with the same name as the existing one and load it into the KnowledgeBuilder?

I manage to remove rules using the following code: statefulKnowledgeSession.getKnowledgeBase().removeRule(knowledgeSetName, ruleName);

I thought that there would be a addRule method somewhere but not luck so far.

The code I’m using to create my KnowledgeBase and StatefulKnowledgeSession is shown below.

All the best,

Pierre

StatefulKnowledgeSession creation code:

StatefulKnowledgeSession ksession;

KnowledgeBuilder kbuilder;

KnowledgeBase kbase;

kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();

kbuilder.add(ResourceFactory.newFileResource(Demo.class.getResource(Demo.drlFile).getPath()), ResourceType.DRL);

if (kbuilder.hasErrors()) {

                System.out.println(kbuilder.getErrors());

}

kbase = KnowledgeBaseFactory.newKnowledgeBase();

kbase.addKnowledgePackages(kbuilder.getKnowledgePackages());

ksession = kbase.newStatefulKnowledgeSession();

ksession.insert(…);

…

ksession.fireAllRules();