ajax 跨域问题 No 'Access-Control-Allow-Origin' header is present on the requested resource

接口：
public String get(HttpServletResponse response) throws Exception {
   response.addHeader("Access-Control-Allow-Origin","*");
   return "hello";
}

如果是静态文件html，则加上<meta http-equiv="Access-Control-Allow-Origin" content="*" />