spring mvc3中的addFlashAttribute方法

记得在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：

 
Java代码 
1.    //第三个参数（UserModel user）默认为绑定对象  
2.    @RequestMapping(value = "/user/save", method = RequestMethod.POST)  
3.    public ModelAndView saveUser(HttpServletRequest request, HttpServletResponse response,UserModel user) throws Exception {  
4.        ModelAndView mv = new ModelAndView("/user/save/result");//默认为forward模式  
5.//      ModelAndView mv = new ModelAndView("redirect:/user/save/result");//redirect模式  
6.        mv.addObject("message","保存用户成功！");  
7.        return mv;  
8.    } 
//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

Java代码 
1.@RequestMapping(value = "/user/save", method = RequestMethod.POST)  
2.public ModelAndView saveUser(UserModel user, RedirectAttributes redirectAttributes) throws Exception {  
3.    redirectAttributes.addFlashAttribute("message", "保存用户成功！");//使用addFlashAttribute,参数不会出现在url地址栏中  
4.    return "redirect:/user/save/result";  
5.} 
@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：


Java代码 
1.<form:form id="myform" action="saveUserDetails.action" method="POST" commandName="user">  
2.   <form:input type="text" name="firstName" path="firstName"/>  
3.   <form:input type="text" name="lastName" path="lastName"/>  
4.   <form:input type="text" name="email" path="email"/>  
5.   <input type="submit" value="submit">  
6.</form:form>  
7.  
<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：

Java代码 
1. 
2.       @RequestMapping(value="/saveUserDetails.action", method=RequestMethod.POST)  
3.public String greetingsAction(@Validated User user,RedirectAttributes redirectAttributes){  
4.              
5.               someUserdetailsService.save(user);  
6.      
7.               redirectAttributes.addFlashAttribute("firstName", user.getFirstName());  
8.    redirectAttributes.addFlashAttribute("lastName", user.getLastName())  
9.    return "redirect:success.html";  
10.} 

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