spring mvc3中 addFlashAttribute 方法

在spring mvc2中，当保存POJO到数据库后,要返回成功页面，如果这个时候要带点信息， 
则要这样： 

 

    //第三个参数（UserModel user）默认为绑定对象
    @RequestMapping(value = "/user/save", method = RequestMethod.POST)
    public ModelAndView saveUser(HttpServletRequest request, HttpServletResponse response,UserModel user) throws Exception {
        ModelAndView mv = new ModelAndView("/user/save/result");//默认为forward模式
//      ModelAndView mv = new ModelAndView("redirect:/user/save/result");//redirect模式
        mv.addObject("message","保存用户成功！");
        return mv;
    }

而在spring mvc 3.1后，可以这样 

@RequestMapping(value = "/user/save", method = RequestMethod.POST)
public ModelAndView saveUser(UserModel user, RedirectAttributes redirectAttributes) throws Exception {
    redirectAttributes.addFlashAttribute("message", "保存用户成功！");//使用addFlashAttribute,参数不会出现在url地址栏中
    return "redirect:/user/save/result";
}

  来个稍微完整点的例子，首先是一个表单，在其中填入一些信息： 

<form:form id="myform" action="saveUserDetails.action" method="POST" commandName="user">
   <form:input type="text" name="firstName" path="firstName"/>
   <form:input type="text" name="lastName" path="lastName"/>
   <form:input type="text" name="email" path="email"/>
   <input type="submit" value="submit">
</form:form>

   则在controller中，可以这样： 

       @RequestMapping(value="/saveUserDetails.action", method=RequestMethod.POST)
public String greetingsAction(@Validated User user,RedirectAttributes redirectAttributes){

               someUserdetailsService.save(user);

               redirectAttributes.addFlashAttribute("firstName", user.getFirstName());
    redirectAttributes.addFlashAttribute("lastName", user.getLastName())
    return "redirect:success.html";
}

  success.html: 
<div> 
<h1>Hello ${firstName} ${lastName}. Your details stored in our database.</h1> 
</div><br> 

  但如果F5的时候，会发现参数丢失，因为flash scope其实只支持redirect的，所以可以判断下： 
 

@RequestMapping(value="/success.html", method=RequestMethod.GET)
    public String successView(HttpServletRequest request){
        Map<String,?> map = RequestContextUtils.getInputFlashMap(request);
        if (map!=null)
           return "success";
        else return "redirect:someOtherView"; //給出其他提示信息