historyService.deleteHistoricProcessInstance(processInstanceId);
今天用上面的代码来删除activiti工作流的流程实例的时候报错了，说流程正在运行无法删除流程实例，报错提示如下所示：
Process instance is still running, cannot delete historic process instance XXXX
解决方法：
将historyService.deleteHistoricProcessInstance(processInstanceId)改成以下代码即可，亲试有效，极力推荐!
runtimeService.deleteProcessInstance(processInstanceId,"");