A. public String index (String username,Map<String,object>map){ map.put("username",username); return "welcome.jsp"; }

B. public String index(String username,Model model){ model.addAttribute (username); return welcome; }

C. public String index(Map<String,Object>map,Stringusername){ map.put("username",username); return "welcome"; }

D. public String index (String username){ Map<String,Object>map=new Map<String,0bject>(); map.put("username",username); return "welcome"; }