And my code :
HornetQHTWorkItemHandler hornetQHTWorkItemHandler = new HornetQHTWorkItemHandler(ksession);
ksession.getWorkItemManager().registerWorkItemHandler("Human Task", hornetQHTWorkItemHandler);
WorkflowProcessInstanceImpl pi = (WorkflowProcessInstanceImpl)ksession.getProcessInstance(processid);
pi.setVariable(param, values);