action不能往jsp中传递数据的问题

struct z中一个action的配置如下:

    path="/library"
    parameter="method"
    name="libraryForm"
    scope="request"
    validate="true"
    type="org.springframework.web.struts.DelegatingActionProxy">

        name="listLibrarys"
        path="/form/listlibrarys.jsp"
        redirect="true" />

action 中部分源代码:

public ActionForward list(ActionMapping mapping, ActionForm form,
   HttpServletRequest request, HttpServletResponse response) {
  log.debug("list library ");

  List list = libraryManagerService.listLibrarys();

  if(list == null) log.debug("there is not any library ,because list is null");
  else log.debug("there are " + list.size() + " librarys .");

  request.setAttribute("list", list) ;
// request.getSession().setAttribute("list", list);
  return mapping.findForward("listLibrarys");
}

jsp中部分源代码:

${library.code}

${library.name}

${library.buildTime}

">添加

">修改

">删除

问题:

一次也不能循环.

在action的 List list = libraryManagerService.listLibrarys();后中加入:

log.debug("list size="+list.size());

运行结果:list size=6.

原因是:

        name="listLibrarys"
        path="/form/listlibrarys.jsp"
        redirect="true" />

中的redirect="true".直接转向后.request中的数据丢失.

改为redirect="false"即可.

redirect 决定了action在使用forward跳转的时候是使用

RequestDispatcher rd = getServletContext().getRequestDispatcher(uri).forward(request, response);

还是

response.sendRedirect(response.encodeRedirectURL(uri));

在structs的类RequestProcessor中processForwardConfig方法里面有如下代码：

if(forward.getRedirect())//判断redirect是否为true
        {
            if(uri.startsWith("/"))
                uri = request.getContextPath() + uri;
            response.sendRedirect(response.encodeRedirectURL(uri));
        } else
        {
            doForward(uri, request, response);
        }

其中的方法doForward如下：

protected void doForward(String uri, HttpServletRequest request, HttpServletResponse response)
        throws IOException, ServletException
    {
        RequestDispatcher rd = getServletContext().getRequestDispatcher(uri);
        if(rd == null)
        {
            response.sendError(500, getInternal().getMessage("requestDispatcher", uri));
            return;
        } else
        {
            rd.forward(request, response);
            return;
        }

这两种跳转方法的区别是：

forward 会将 request state , bean 等等信息带往下一个 jsp

redirect 是送到 client 端后，再由client向服务器发送request,服务器接收到后来发的request中已经不包含上次的request的state，bean等信息了。所以在jsp中就接收不到相应的数据

来源：oschina

链接：https://my.oschina.net/u/96267/blog/6814

标签

jsp

library

request