Activiti人员分配有关问题

Activiti人员分配问题
<userTask id="theTask" name="my task" activiti:candidateUsers="kermit, gonzo" />
或者映射到监听的类上

这是在activit官网文档上写的 用于人员的绑定

public class TestTask implements TaskListener {

	ProcessEngine ps = ProcessEngineConfiguration.createProcessEngineConfigurationFromResourceDefault().buildProcessEngine();
	@Override
	public void notify(DelegateTask delegateTask) {
		DelegateExecution ex = delegateTask.getExecution();
		IdentityService is = ps.getIdentityService();
		User u1 = is.newUser("userid1");
		u1.setFirstName("userid1");
		u1.setLastName("userid1");
		User u2 = is.newUser("userid2");
		u2.setFirstName("userid2");
		u2.setLastName("userid2");
		is.saveUser(u1);
		is.saveUser(u2);
		TaskService ts = ps.getTaskService();
		Map map = new HashMap();
		map.put("a", "userid1");
		map.put("b", "userid2");
		Collection<String> c = map.values();
		Iterator it = c.iterator();
		while(it.hasNext()){
			System.out.println(it.next().toString());
		}
		delegateTask.addCandidateUsers(c);

上面是实现监听的类 流程定义的任务就直接映射到这个类（监听create事件） 但是用户初始化啦任务却没有绑定上我设置的候选人。