I ran into a problem with accessing boolean properties of an eventListener.
I've attached a patch to trunk of ./modules/pvm/src/test/java/org/jbpm/pvm/internal/wire/ObjectWireTest.java that adds a test that exposes this problem.

Basically, the example below fails with the error
"org.jbpm.pvm.internal.wire.WireException: couldn't initialize object 'null': couldn't find property setter setCreateXml for value true"

JPDL-fragment:
<event-listener expr="#

">
<property name="createXml">
<true/>
</property>
</event-listener>

Java-fragment:
public void setCreateXml(boolean createXml)

Workaround: changing the Java-side to use a Boolean instead of a boolean for the method parameter.

While there is a workaround, I will still suggest supporting both Boolean and boolean-based setters.