@RequestMapping("ajaxReq")
public void ajaxReq(HttpServletRequest req,HttpServletResponse resp) throws IOException{
    resp.setCharacterEncoding("utf-8");
    resp.setContentType("text/html;charset=utf-8");
    String username = req.getParameter("username");
    String password = req.getParameter("password");             
    resp.getWriter().write(username+" : "+password);
}
    

@RequestMapping(value="ajaxReq",produces="text/html;charset=utf-8")
@ResponseBody
public String ajaxReq(HttpServletRequest req,HttpServletResponse resp) throws IOException{
    String username = req.getParameter("username");
    String password = req.getParameter("password");
    return username+" : "+password;
}