Rails 状态码

Response Class  HTTP StatusCode   Symbol
Informational   100               :continue
Success         200               :ok
Redirection     300               :multiple_choices
                301               :moved_permanently(重定向)
                304               :not_modified
Client Error    400               :bad_request
                401               :unauthorized
                403               :forbidden
                404               :not_found
Server Error    500               :internal_server_error
                502               :bad_gateway