SPF 记录：原理、语法及配置方法简介
February 17, 2014 / 编程指南
SPF，全称为 Sender Policy Framework，即发件人策略框架。
环境：
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问题:
@GetMapping(value = {"", "/"})
public void toIndex(HttpServletRequest request, HttpServletResponse response, Model model) throws IOException {
response.setStatus(HttpServletResponse.SC_MOVED_PERMANENTLY);
response.setHeader("Location", Constants.url + "/en");
// response.sendRedirect("/en");
}