I just followed the example BPMN2-ServiceProcess.bpmn2 to create a process that executes a given java class, and to test that example the following is done:
KnowledgeBase kbase = createKnowledgeBase("BPMN2-ServiceProcess.bpmn2");
StatefulKnowledgeSession ksession = createKnowledgeSession(kbase);
ksession.getWorkItemManager().registerWorkItemHandler("Service Task", new ServiceTaskHandler());
I assumed this would be the procedure to create a process that executes a given method of a given java class (as shown in the example).
I will continue reading the doc and try to use the Task Client.
Thank you so far :)