jbpm4怎样做回退？怎样取得“回退节点”的处理人？

目前没有人会！！！！！！！！！！

 我是这样取回退节点的处理人的：

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Configuration configuration = new Configuration();

ProcessEngine pe = configuration.buildProcessEngine();

//通过taskid取executionId

String executionId = pe.getTaskService().getTask(taskid).getExecutionId();

//

List <HistoryTask>list = pe.getHistoryService().createHistoryTaskQuery().executionId(executionId).list();

for(int i=0;i<list.size();i++){

Task task = pe.getTaskService().getTask(list.get(0).getId());

if(task.getName().equalsIgnoreCase(decision.replaceAll("退回", ""))){

selectDecisionUsers = new SelectItem[1];

selectDecisionUsers[0]=new SelectItem(task.getAssignee(),task.getAssignee());

}

}