11

如何为牛仔休息处理程序启用 CORS？我尝试添加 options/2 方法，如下所示：

options(Req, State) ->
    {[
       {<<"access-control-allow-origin">>, <<"*">>},
       {<<"access-control-allow-methods">>, <<"GET, OPTIONS">>}
     ], Req, State}.

但这会导致错误，例如：

Error in process <0.263.0> with exit value: {{case_clause,{[{<<27 bytes>>,<<1 byte>>},{<<28 bytes>>,<<12 bytes>>}],{http_req,#Port<0.2636>,ranch_tcp,keepalive,<0.263.0>,<<7 bytes>>,{1,1},{{127,0,0,1},56522},<<9 bytes>>,undefined,9090,<<8 bytes>>,undefined,<<0 bytes>>,undefined,<<0 bytes>>,[],[{<<4 bytes>>,<<14 bytes>>},{<<10 bytes>>,<<74 bytes>>},{<<6 bytes>>,<<63 bytes>>},{<<15 bytes>>,<<14 bytes>>},{<<15 bytes>>,<<13 bytes>>},{<<6 bytes>>,<<4 bytes>>},{<<29 bytes>>,<<3 bytes>>},{<<30 bytes>>,<<16 bytes>>},{<<10 bytes>>,<<10 bytes>>}],[{<<10 bytes>>,[<<10 bytes>>]}],undefined,[],waiting,undefined,<<0 bytes>>,false,waiting,[],<<0 bytes>>,undefined},undefined...

我的错误在哪里？

4

4 回答 4

14

牛仔文档说您需要使用 set_resp_headers 设置标题，而不是返回标题列表：

 %% If you need to add additional headers to the response at this point,
 %% you should do it directly in the options/2 call using set_resp_headers.

所以你的代码应该是这样的：

options(Req, State) ->
    Req1 = cowboy_req:set_resp_header(<<"access-control-allow-methods">>, <<"GET, OPTIONS">>, Req),
    Req2 = cowboy_req:set_resp_header(<<"access-control-allow-origin">>, <<"*">>, Req1),
    {ok, Req2, State}.

你可以用

curl -H "Origin: http://example.com" \
  -H "Access-Control-Request-Method: GET" \
  -H "Access-Control-Request-Headers: X-Requested-With" \
  -X OPTIONS --verbose \
http://localhost:8080
* About to connect() to localhost port 8080 (#0)
*   Trying 127.0.0.1... connected
* Connected to localhost (127.0.0.1) port 8080 (#0)
> OPTIONS / HTTP/1.1
> User-Agent: curl/7.21.4 (universal-apple-darwin11.0) libcurl/7.21.4 OpenSSL/0.9.8r     zlib/1.2.5
> Host: localhost:8080
> Accept: */*
> Origin: http://example.com
> Access-Control-Request-Method: GET
> Access-Control-Request-Headers: X-Requested-With
>
< HTTP/1.1 200 OK
< connection: keep-alive
< server: Cowboy
< date: Mon, 25 Mar 2013 15:59:11 GMT
< content-length: 0
< access-control-allow-methods: GET, OPTIONS
< access-control-allow-origin: *
<
* Connection #0 to host localhost left intact
* Closing connection #0
于 2013-03-25T16:00:47.343 回答
1

我的 REST 仅在提供令牌的情况下才允许访问资源。所以我必须实现is_authorized/2对 OPTIONS 和 GET 请求不同的回调。见下文：

1) 实现options/2如下

options(Req0, State) ->
  % cors
  Req1 = cowboy_req:set_resp_header(
    <<"access-control-allow-methods">>, <<"GET, OPTIONS">>, Req0),
  Req2 = cowboy_req:set_resp_header(
    <<"access-control-allow-origin">>, <<"*">>, Req1),
  Req3 = cowboy_req:set_resp_header(
    <<"access-control-allow-headers">>, <<"authorization">>, Req2),
  {ok, Req3, State}.

2) 实现is_authorized/2如下

is_authorized(Req, State) -> 
  case cowboy_req:method(Req) of
    <<"GET">> ->
      case cowboy_req:parse_header(<<"authorization">>, Req) of
        {bearer, <<Token/binary>>} ->
          {true, Req, Token};
        _ ->
          {{false, <<"Basic realm=\"cowboy\"">>}, Req, State}
      end;
    <<"OPTIONS">> ->
      {true, Req, State}
  end.

3)to_json/2方法发送access-control-allow-origin

to_json(Req0, State) ->
  R = #{ foo => [<<"bar">>] },
  % cors
  Req1 = cowboy_req:set_resp_header(
      <<"access-control-allow-origin">>, <<"*">>, Req0),
  Body = jsx:encode(R),
  {Body, Req1, State}.
于 2017-02-15T12:23:12.390 回答
0

除了在这里找到的答案之外，Cowboy 2.* 似乎还有一个中间件功能，您可以使用它来拦截对服务器的所有 REST 处理程序请求，并添加所需的响应标头： https ://ninenines.eu/docs/en /cowboy/2.7/guide/middlewares/

可以在这个 Github gist 中找到一个示例 CORS 中间件实现： https ://github.com/ninenines/cowboy/blob/master/examples/markdown_middleware/src/markdown_middleware_app.erl

于 2020-01-04T22:30:04.083 回答
0

你可以试试这个：

Req1 = cowboy_req:set_resp_header(<<"access-control-allow-origin">>, <<"*">>, Req0 -> Worked for me.
于 2019-09-25T17:02:38.430 回答