form表单提交返回页面alert弹窗提示

//在action方法中，方法的返回里
HttpServletResponse response=ServletActionContext.getResponse();
response.setCharacterEncoding("UTF-8");
response.setContentType("text/html; charset=utf-8");
PrintWriter out=response.getWriter();
out.print("<script>alert('用户名或者密码错误，请重新登录');history.go(-1);</script>");
return null;