[rules-dev] Spring integration for Drools has landed.

[Mark Proctor]

http://blog.athico.com/2009/10/spring-integration-for-drools-has.html


      Spring integration for Drools has landed.
      <http://blog.athico.com/2009/10/spring-integration-for-drools-has.html>


Posted by Mark Proctor

I've just committed the first end to end working Spring integration for 
Drools. There is still lots more to do, but it at least now allows for 
end to end working examples. The latest build that includes this work 
can be found from hudson here:
https://hudson.jboss.org/hudson/job/drools/lastSuccessfulBuild/artifact/trunk/target/

So how does it work. Lets look at the unit test for more details. The 
beans.xml 
<http://fisheye.jboss.org/browse/JBossRules/trunk/drools-container/drools-spring/src/test/resources/org/drools/container/spring/beans.xml?r=29780> 
provides a configuration for KnowledgeBases, StatefulKnowledgeSession, 
StatelessKnowledgeSession and the ServiceManager. KnowledgeBases can be 
confired from a list of resources, that work in the same way that 
changeset xml does. This allows resources to be pulled from any URL 
resolveble location, be it classpath, localdisk or from artifacts 
published from Guvnor:

<drools:kbase id="kbase1">
 <drools:resource source="classpath:org/drools/container/spring/testSpring.drl" type="DRL"/>
 <drools:resource source="classpath:org/drools/container/spring/IntegrationExampleTest.xls" type="DTABLE">
     <drools:decisiontable-conf input-type="XLS" worksheet-name="Tables_2"/>
 </drools:resource>
</drools:kbase>

The above xml shows a KnowledgeBase configured from a DRL and a XLS, 
remember we could have added DRFs if we wanted workflow in there too.

That KnowledgeBase is now a bean that can be referenced via the id 
"kbase1". From that bean we can now create sessions. The "type" 
attribute specifies whether the session is stateful or stateless:

<drools:ksession id="ksession1" type="stateless" kbase="kbase1"/>
<drools:ksession id="ksession2" type="stateful" kbase="kbase1"/>


Those sessions are now beans and can be injected into your own classes 
using Spring annotations, or used to configure up a Drools ServiceManager.

<drools:serviceManager id="sm1">
  <drools:register name="stateless1" ref="ksession1"/>
   <drools:register ref="ksession2"/>
</drools:serviceManager>

The ServiceManager is a new class that I haven't mentioned before that 
will be in the upcoming Drools 5.1. The ServiceManager can be worked 
with both locally and remotely. It allows sessions to be created and 
registered all seamlessly, whether it's local or remote and those 
sessions are also exposed both locally and remotely. This ties in with 
the Camel <http://camel.apache.org/>work we are doing to make it easy to 
work with Drools out of the box in a service and remoting environment 
and should hopefully provide the ultimate in event driven architectures. 
I'll blog more on those pieces as they fall into place.

The XSD can be found here: spring-drools.xsd 
<http://fisheye.jboss.org/browse/JBossRules/trunk/drools-container/drools-spring/src/main/resources/drools-spring.xsd?r=29780>

Once the xml is in place, using it with Spring is a doddle and you can 
look at the two unit tests 
<http://fisheye.jboss.org/browse/JBossRules/trunk/drools-container/drools-spring/src/test/java/org/drools/container/spring/SpringDroolsTest.java?r=29780> 
to see this in action:

    public void test1() throws Exception {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext( "org/drools/container/spring/beans.xml" );

        List list = new ArrayList();
        StatelessKnowledgeSession kstateless = (StatelessKnowledgeSession) context.getBean( "ksession1" );
        kstateless.setGlobal( "list", list );
        kstateless.execute( new Person( "Darth", "Cheddar", 50 ) );
        assertEquals( 2, list.size() );

        list = new ArrayList();
        StatefulKnowledgeSession kstateful = (StatefulKnowledgeSession) ((StatefulKnowledgeSession) context.getBean( "ksession2" ));
        kstateful.setGlobal( "list", list );
        kstateful.insert( new Person( "Darth", "Cheddar", 50 ) );
        kstateful.fireAllRules();
        assertEquals( 2, list.size() );
    }

    public void test2() {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext( "org/drools/container/spring/beans.xml" );

        ServiceManager sm = (ServiceManager) context.getBean( "sm1" );

        List list = new ArrayList();
        StatelessKnowledgeSession kstateless = (StatelessKnowledgeSession) sm.lookup( "stateless1" );
        kstateless.setGlobal( "list", list );
        kstateless.execute( new Person( "Darth", "Cheddar", 50 ) );
        assertEquals( 2, list.size() );

        list = new ArrayList();
        StatefulKnowledgeSession kstateful = (StatefulKnowledgeSession) sm.lookup( "ksession2" );
        kstateful.setGlobal( "list" list );
        kstateful.insert( new Person( "Darth", "Cheddar", 50 ) );
        kstateful.fireAllRules();
        assertEquals( 2, list.size() );
    }

There is still lots more to do, especially around exposing actual 
configuration information (JPA etc) and initial setup data (globals, 
inserted facts) along with extending this to work with Camel. So if you 
want to help, you know where to find us :)
IRC <http://labs.jboss.org/drools/irc.html>
Mailing Lists <http://labs.jboss.org/drools/lists.html>
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