默认情况下，只有七种 simple response headers（简单响应首部）可以暴露给外部：

  Cache-Control
  Content-Language
  Content-Length
  Content-Type
  Expires
  Last-Modified
  Pragma

所以，想暴露Authorization给前端 需要设置响应首部 Access-Control-Expose-Headers

public boolean preHandle(HttpServletRequest httpServletRequest,
                             HttpServletResponse httpServletResponse,
                             Object object) throws Exception{
        httpServletResponse.setHeader("Access-Control-Expose-Headers","Authorization");
        return true;
}