Spring MVC alert prompt in the original page

 A wording:

    @RequestMapping("/testAlert") 
    public ModelAndView pay(HttpServletResponse response) throws IOException{
        response.setContentType("text/html;charset=utf-8");
        PrintWriter out = response.getWriter();
        out.print("<script type='text/javascript'>alert('成功!');</script>");  
        ModelAndView mv=new ModelAndView();
        mv.setViewName("index");
        return mv;
    }        

Writing two (forward while the pop-up dialog box):

@RequestMapping(value="/user/index",method=RequestMethod.POST)
public String checkLogin(@RequestParam("userName") String userName,
                         @RequestParam("password") String password,
                         HttpServletResponse response) throws IOException{
　　　　//根据用户名userName和密码password查看是否是非法用户，此处代码略
　　　　response.setContentType("text/html;charset=gb2312");
　　　　PrintWriter out = response.getWriter();
　　　　if(非法用户){
    　　　　out.print("<script language=\"javascript\">alert('登录失败！');window.location.href='/你的工程名/login'</script>");    
            //弹窗提示并跳转到其他页面
    　　　　return "/login";
　　　　}
　　　　return "/user/index";　
　}
 

Written three:

@RequestMapping("/testAlert.do")
	public void deleteNews(HttpServletResponse response) {
		response.setContentType("text/html;charset=utf-8");
                PrintWriter writer = response.getWriter();
		msg = "alert('删除失败');history.go(-1)";    //回到上一个页面
		writer.print("<script type='text/javascript'>" + msg + "</script>");
		writer.flush();
		writer.close();
        catch (IOException e1) {
		e1.printStackTrace();
		}
	}