I meet working a simple example to interiorize with jboss rules and I obtain the following error:
 

Exception in thread "main" org.drools.rule.InvalidRulePackage: Unable to create Field Extractor for 'CantSegundos' : [Rule name=Valida Duracion nula, agendaGroup=MAIN, salience=0, no-loop=false]

org.drools.RuntimeDroolsException
: org.drools.RuntimeDroolsException : java.lang.NullPointerExceptionUnable to create Field Extractor for 'CantSegundos' : [Rule name=valida Duracion , agendaGroup=MAIN, salience=0, no-loop=false]

org.drools.RuntimeDroolsException

: org.drools.RuntimeDroolsException: java.lang.NullPointerException

at org.drools.rule.Package.checkValidity(

Package.java:408)

at org.drools.common.AbstractRuleBase.addPackage(

AbstractRuleBase.java:288)

at prototipo.Prueba.main(

Prueba.java:27)

the class main is:

public

 static final void main(String[] args) throws Exception {

             final PackageBuilder builder = new PackageBuilder();

            builder.addPackageFromDrl(

new InputStreamReader( Prueba.class .getResourceAsStream( "regla.drl" ) ) );

            final RuleBase ruleBase = RuleBaseFactory.newRuleBase();

           ruleBase.addPackage( builder.getPackage() );

            final StatefulSession session = ruleBase.newStatefulSession();

          Integer segundos =

new Integer(5);

            validaciones valida =

new validaciones();

           valida.setCantSegundos(segundos);

          session.insert( valida);

           session.fireAllRules();

in the rules is:

package

 prototipo

import prototipo.validaciones;

rule "Valida Duracion nula"

when

           v : validaciones(CantSegundos == 0)

then

              v.setResultado(

"I");

             System.out.println(

"obtenemos" + v.getResultado() );

end

rule "valida Duracion " when

              v : validaciones(CantSegundos > 0)

then

           v.setResultado(

"S");

            System.out.println(

"obtenemos" + v.getResultado());

end

Thank you for helping me.