Drools & jBPM provide an knowledge-centric API, where rules and processes are first class citizens.
The most common interfaces you will use are:
Factory classes, with static methods, provide instances of the above interfaces. A pluggable provider approach is used to allow provider implementations to be wired up to the factories at runtime. The Factories you will most commonly used are:
A Typical example to load a rule resource.
KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder(); kbuilder.add( ResourceFactory.newUrlResource( url ), ResourceType.DRL ); if ( kbuilder.hasErrors() ) { System.err.println( builder.getErrors().toString() ); } KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase(); kbase.addKnowledgePackages( builder.getKnowledgePackages() ); StatefulKnowledgeSession ksession = knowledgeBase.newStatefulKnowledgeSession(); ksession.insert( new Fibonacci( 10 ) ); ksession.fireAllRules(); ksession.dispose();
A Typical example to load a process resource. Notice the ResourceType is changed to BPMN2 in this example.
KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder(); kbuilder.add( ResourceFactory.newUrlResource( url ), ResourceType.BPMN2 ); KnowledgeBase kbase = kbuilder.newKnowledgeBase(); StatefulKnowledgeSession ksession = knowledgeBase.newStatefulKnowledgeSession(); ksession.startProcess( "Buy Order Process" ); ksession.dispose();
'kbuilder', 'kbase', 'ksession' are the variable identifiers often used, the k prefix is for 'knowledge'.
It is also possible to configure a KnowledgeBase using configuration, via a xml change set, instead of programmatically. Here is a simple change set:
<change-set xmlns='http://drools.org/drools-5.0/change-set' xmlns:xs='http://www.w3.org/2001/XMLSchema-instance' xs:schemaLocation='http://drools.org/drools-5.0/change-set change-set-5.0.xsd' > <add> <resource source='classpath:org/domain/someRules.drl' type='DRL' /> <resource source='classpath:org/domain/myProcess.bpmn2' type='BPMN2' /> </add> </change-set>
And it is added just like any other ResourceType
KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder(); kbuilder.add( ResourceFactory.newUrlResource( url ), ResourceType.ChangeSet );
The majority of knowledge API is considered stable and should not change, experimental classes and API's will be marked as such.