java - the map of the model always returns an empty object -

good evening, have spring mvc project on e-commerce site. concerning cart management, when add product cart clicking "ajouter au panier", adds good, problem if add product, show second product . made "println" , noticed "model.asmap (). (" panier ")" returns null. problem please? here screen prints on console, controller , index.jsp

controller

@requestmapping(value = "/ajouteraupanier")     public string ajouteraupanier(@requestparam long idarticle, @requestparam int quantite, model model) {         system.out.println("111111111111111111111111111111111111111111111");         panier panier = null;          if (model.asmap().get("panier") == null) {             system.out.println("222222222222222222222222222222222222222222222");             panier = new panier();             system.out.println("333333333333333333333333333333333333333333333");             model.addattribute("panier", panier);             system.out.println("9999999999999999999999999999999" + panier.getitems().size());         } else system.out.println("555555555555555555555555555555555555555555555");          panier = (panier) model.asmap().get("panier");         panier.addarticle(metier.getarticle(idarticle), quantite);         model.addattribute("categories", metier.listcategories());         model.addattribute("articles", metier.listarticles());         return "index";     }