Using Drools I got this El-Exception: org.jbpm.graph.def.DelegationException

[mikool]

Hi all!

I started to use drools in my processes and have this task in my processdefinition:

<task-node name="TaskXYZ">
   <task name="TaskXYZ">
     <assignment handler="org.jboss.seam.drools.DroolsAssignmentHandler">
            <workingMemoryName>someXyzApprovalMemory</workingMemoryName>
            <assertObjects>
                <element>#{actor}</element>
            </assertObjects>
            </assignment>
   </task>
   <transition to="Task2" name="toTask2"></transition>
</task-node>

And additionaly I created my rule:

package com.mike.xyz.bpm

import org.jbpm.taskmgmt.exe.Assignable

global Assignable assignable
global Actor actor

rule "assignment"
  when
    Actor( actor-id == "mike" )
  then
    assignable.setActorId( "mike" );
end

When I execute my process I get this error:

javax.el.ELException: org.jbpm.graph.def.DelegationException
     at org.jboss.el.util.ReflectionUtil.invokeMethod(ReflectionUtil.java:333)
...

but I cannot see what I've done wrong.
My rule files are in the EarContent/rules directory. And my components.xml has this entry:

<drools:rule-base name="assignment">
   <drools:rule-files>
        <value>rules/assignment.drl</value>
    </drools:rule-files>
</drools:rule-base>

Please, give me some hints.
Many thanks.

Mike