Handlers¶

Plain HTTP handlers:

init(Req, State) ->
  {ok, Req, State}.

% 立即返回请求
init(Req0, State) ->
  Req = cowboy_req:reply(200, #{
      <<"content-type">> => <<"text/plain">>
  }, <<"Hello World!">>, Req0),
  {ok, Req, State}.

Other handlers:

可有选项:
  1. cowboy_rest
  2. cowboy_websocket
  3. cowboy_loop
如:
init(Req, State) ->
  {cowboy_websocket, Req, State}.

Cleaning up:

terminate(_Reason, _Req, _State) ->
  ok.

Loop handlers:

循环处理程序用于响应可能无法立即可用的请求，但您希望在响应到达时保持连接打开一段时间。
这种做法最着名的例子被称为长轮询。
也适用 server-sent events,用于响应partially available请求

% Initialization,初使化
init(Req, State) ->
  {cowboy_loop, Req, State}.
init(Req, State) ->
  {cowboy_loop, Req, State, hibernate}.

% Receive loop,收到消息后处理
info({reply, Body}, Req, State) ->
    cowboy_req:reply(200, #{}, Body, Req),
    {stop, Req, State};
info(_Msg, Req, State) ->
    {ok, Req, State, hibernate}.

% Streaming loop
init(Req, State) ->
  Req2 = cowboy_req:stream_reply(200, Req),
  {cowboy_loop, Req2, State}.

info(eof, Req, State) ->
    {stop, Req, State};
info({event, Data}, Req, State) ->
    cowboy_req:stream_body(Data, nofin, Req),
    {ok, Req, State};
info(_Msg, Req, State) ->
    {ok, Req, State}.

Static files:

PS:最好使用cdn解决此问题
% 文件
{"/", cowboy_static, {priv_file, my_app, "static/index.html"}}
{"/", cowboy_static, {file, "/var/www/index.html"}}

% 目录
{"/assets/[...]", cowboy_static, {priv_dir, my_app, "static/assets"}}
{"/assets/[...]", cowboy_static, {dir, "/var/www/assets"}}

Customize the mimetype detection:
% 默认mimetype
{"/assets/[...]", cowboy_static, {priv_dir, my_app, "static/assets",
                          [{mimetypes, cow_mimetypes, web}]}}

{"/assets/[...]", cowboy_static, {priv_dir, my_app, "static/assets",
                          [{mimetypes, cow_mimetypes, all}]}}

% 此函数的返回值参见下一条
{"/assets/[...]", cowboy_static, {priv_dir, my_app, "static/assets",
                          [{mimetypes, Module, Function}]}}

{"/", cowboy_static, {priv_file, my_app, "static/index.html",
                          [{mimetypes, {<<"text">>, <<"html">>, []}}]}}


Generate an etag:
{"/assets/[...]", cowboy_static, {priv_dir, my_app, "static/assets",
                          [{etag, Module, Function}]}}

{"/assets/[...]", cowboy_static, {priv_dir, my_app, "static/assets",
                          [{etag, false}]}}