title: SessionAttributes and redirect
body: <p>I have a SessionAttributes key on a Controller that I set in a method </p>
  
  <pre><code>@Controller
  @RequestMapping(method = RequestMethod.POST, value="/")
  @SessionAttributes("approve")
  public class MyController{
    @RequestMapping
    public String do(
          @ModelAttribute("vo") CommandVO vo,
          @RequestParam("approve") boolean approve,
          BindingResult result,
          ModelMap model,
          RedirectAttributes redirectAttributes,
          NativeWebRequest request
    )
    model.setAttribute("approve",approve);
    [...]
    return "redirect:/bla";
  }
  </code></pre>
  
  <p>The variable doesn't end up in the session.</p>
  
  <p>Is it possible that the redirect creates a problem here?</p>