跨域问题和response

// 跨域问题
// 返回前台
HashMap<String, Object> map = new HashMap<String, Object>();
map.put("status", false);
map.put("msg", "文件不存在");
response.setHeader("Access-Control-Allow-Origin", "*");
response.getWriter().print(JSON.toJSON(map));
return;

String token = request.getHeader("token");            // 获取请求头
String params = request.getParameter("params");        // 获取参数值