action中的代码： public ActionForward execute(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response) {
ActionForward result=null;
List<Navigations> listNavigation=null;
List<List<Navigations>> list=null;
List<Banners> listBanner=banner.getAll("");
for(Banners bb:listBanner){
listNavigation=navigation.getListPage
(0, 5, "from Navigations where bid="+bb.getId());
System.out.println("栏目"+bb.getId());
list.add(listNavigation);

for(Navigations nn:listNavigation){
System.out.println("nname="+nn.getNaname());


}
}
request.setAttribute("listBanner", listBanner);
request.setAttribute("list",list);

result=mapping.getInputForward();
return result;
我用debug跟踪了一下 发现到了list.add(listNavigation);这句就出错 这是为什么？？？
还有我在jsp页面用这样一段代码 来输出 你们看看对不对
                  <c:forEach var="listBanner" items="${listBanner}">
<c:out value="${listBanner.bname}" /><br>
<c:forEach var="list" items="${list}">
<c:out value="${list.listNavigation.naname}"></c:out>
</c:forEach>
</c:forEach>