controller分支实现前台显示弹框同时转发

controller分支实现前台显示弹框，前台不需要进行什么操作，前台请求后台的分支即可。

controller层(标红的地方是（alert('账号或密码错误！请重新输入！！！！') window.location.href='/index.jsp'）：弹出一个弹框，然后跳转一个页面，如果你只想弹个弹框可以把跳转的页面去掉。)：

@RequestMapping("/isLogin")
   public Object isLogin(HttpServletRequest request, String uname, String upwd, HttpServletResponse response) throws IOException {
       Userinfo userinfo=new Userinfo();
       userinfo.setUname(uname);
       userinfo.setUpwd(upwd);
       Userinfo login = service.login(userinfo);
       response.setContentType("text/html;charset=utf-8");
       PrintWriter out=response.getWriter();
       if (login!=null){
           System.out.println("0");
           return "/index.jsp";
       }else {
           //out.print("<script language=\"javascript\">alert('登录失败！');</script>");
           out.print("<script language=\"javascript\">alert('账号或密码错误！请重新输入！！！！');window.location.href='/index.jsp'</script>");
           System.out.println("1");
           return out;
       }
 
   }

　　页面：

<%@ page language="java" contentType="text/html; utf-8" isELIgnored="false" pageEncoding="utf-8" %>
 
<html>
<title>我是登录</title>
<body>
<h2>Hello World!</h2>
 
 
<form action="/isLogin" method="post" >
    用户：<input type="text" name="uname"><br>
    密码：<input type="text" name="upwd"><br><br>
    <input type="submit" value="确定登录">
               <button><a href="uen.jsp">点击注册</a></button>
</form>
 
</body>
</html>