获取不到request的attribute

我在servlet里面的语句：ArrayList <introducer> result = PerHandle.queryind(level,name);
   request.setAttribute("introducer", result);

然后传递给queryintroducer。jsp

然后获取： ArrayList<introducer> tem =(ArrayList<introducer>) request.getAttribute("introducer");
if(tem==null) System.out.print(6); 它一直输出6 为什么获取不到 大家帮忙看看啊