java - Passing model attribute during redirect in spring MVC and avoiding the same in URL

Question

My objective is to pass model attributes from controller to JSP page during a redirect and avoid the attribute being displayed in URL. The source code below is validating login from datastore using java data objects.

Controller:

@Controller
public class LoginController {
    int count;
    PersistenceManager pm = PMF.get().getPersistenceManager();

    //Instance of data class
        User user;
    ModelAndView modelAndView=new ModelAndView();

    @RequestMapping(value="/Login",method = RequestMethod.POST)
    public ModelAndView loginValidate(HttpServletRequest req){

        //Getting login values
        String uname=req.getParameter("nameLogin");
        String pswd1=req.getParameter("pswdLogin");
        count=0;


        user=new User();

        //Generating Query
        Query q = pm.newQuery(User.class);
        q.setFilter("userName == userNameParam");
        q.declareParameters("String userNameParam");

        try{
            List<User> results = (List<User>) q.execute(uname);  
            for (User u: results) {

                String userName=u.getUserName();

                if(userName.equals(uname)){

                    System.out.println(u.getPassword());

                    if(u.getPassword().equals(pswd1)){
                        count=count+1;
                        modelAndView.setViewName("redirect:welcome");
                        modelAndView.addObject("USERNAME",uname);
                        return modelAndView;

                    }
         //rest of the logic 
    }

JSP:

 <h1>Welcome ${USERNAME} </h1>

My current URL is /welcome?USERNAME=robin
My goal is to display it as /welcome
Also, my page is supposed to display "Welcome robin" whereas it displays only Welcome.

Answer 1

RedirectAttributes only work with RedirectView, please follow the same

@RequestMapping(value="/Login",method = RequestMethod.POST)
public RedirectView loginValidate(HttpServletRequest req, RedirectAttributes redir){
...

    redirectView= new RedirectView("/foo",true);
    redir.addFlashAttribute("USERNAME",uname);
    return redirectView;
}

Those flash attributes are passed via the session (and are destroyed immediately after being used - see Spring Reference Manual for details). This has two interests :

• they are not visible in URL
• you are not restricted to String, but may pass arbitrary objects.