请教各位高手，下面这段代码看不太懂，帮忙解释一下：
protected void executeQuery(BaseObject obj, ActionMapping mapping,
ActionForm form, HttpServletRequest request,
HttpServletResponse arg4) throws Exception {
Object object = request.getSession().getAttribute(PAGE_HOLDER);
RefreshablePagedListHolder holder = null;
if (object == null) {
MmPartNoDAO dao = (MmPartNoDAO) this
.getBean(MmPartNoDAO.MM_PART_NO_J);
holder = new RefreshablePagedListHolder(dao);
holder.setPageSize(getPageSize(request));
} else {
holder = (RefreshablePagedListHolder) object;
}
holder.setFilter(obj);
request.getSession().setAttribute(PAGE_HOLDER, holder);
}
protected String assignHolder() {
return PAGE_HOLDER;
}
谢谢啦！！！提前祝大家中秋节快乐啊！^-^