el表达式只能取到一部分值

el表达式中能取到数据库的其他值，但是id这个值一直无法获取，一直返回为null


/>
${i.id}
${i.title}
${i.author}
${i.date}
${i.hit}
${i.typeName}
预览
编辑
onclick="if(!confirm('确定要删除吗？')) return
false;">删除

/c:forEach

                            @RequestMapping("/queryAll")
public String queryAll(@RequestParam(value = "PageNum",defaultValue = "1")Integer PageNum,
                       ModelMap model)throws Exception{
    model.addAttribute("PageNum",PageNum);
    model.addAttribute("informationList",informationService.queryAll((PageNum-1)*size,15));
    model.addAttribute("total",informationService.queryCount());
    return "base/information/list";
}

    @RequestMapping("/preview")
public String preview(@RequestParam Integer id,ModelMap model)throws Exception{
    model.addAttribute("preview",informationService.findById(id));
    System.out.println("id = "+id);
    return "base/information/preview";
}

@RequestMapping("/preview")
public String preview(@RequestParam Integer id,ModelMap model)throws Exception{
model.addAttribute("preview",informationService.findById(id));
System.out.println("id = "+id);
return "base/information/preview";