牛仔邮政处理程序

Question

尝试接收 POST 请求并将其存储到 ETS 表中

这里是代码

init(Req0, Opts) ->
    Method = cowboy_req:method(Req0),
    HasBody = cowboy_req:has_body(Req0),
    Req = maybe_echo(Method, HasBody, Req0),
    {ok, Req, Opts}.

maybe_echo(<<"POST">>, true, Req0) ->
    {ok, PostVals, Req} = cowboy_req:read_urlencoded_body(Req0),
    Echo = proplists:get_value(<<"echo">>, PostVals),
    echo(Echo, Req);

maybe_echo(<<"POST">>, false, Req) ->
    cowboy_req:reply(400, [], <<"Missing body.">>, Req);

maybe_echo(_, _, Req) ->
    %% Method not allowed.
    cowboy_req:reply(405, Req).

echo(undefined, Req) ->
    cowboy_req:reply(400, [], <<"Missing echo parameter.">>, Req);

echo(Echo, Req) ->
Inf = #news{id=25, created=today, article=Echo},
    case ets:insert(news, {Inf#news.id, Inf#news.created, Inf#news.article}) of
        true -> cowboy_req:reply(200, #{<<"content-type">> => <<"text/plain; charset=utf-8">>}, Echo, Req);
        _        -> 
            Error = <<"{\"error\": \"error\"}">>,
            cowboy_req:reply(200, #{<<"content-type">> => <<"text/plain; charset=utf-8">>}, Error, Req)
    end.

当我卷曲时：

$ curl -i -H "Content-Type: application/json" -X POST -d echo='{"action":"insert","key":"some_key", "value":[1, 2,3]}'http://localhost:8080/

我收到了错误：

=错误报告==== 2017 年 1 月 29 日::18:57:21 === 牧场监听器 http，连接进程 ，流 1 的请求进程 退出，原因为 badarg 和堆栈跟踪 [{ets,insert,[news,{25,today,>}],[]},{post_handler,echo, 2,[{file,"e:/_dev/news/_build/default/lib/news/src/post_handler.erl"},{line,25}]},{post_handler,init,2,[{file," e:/_dev/news/_build/default/lib/news/src/post_handler.erl"},{line,8}]},{cowboy_handler,execute,2,[{file,"e:/_dev/news/ _build/default/lib/cowboy/src/cowboy_handler.erl"},{line,39}]},{cowboy_stream_h,execute,3,[{file,"e:/_dev/news/_build/default/lib/cowboy /src/cowboy_stream_h.erl"},{line,173}]},{cowboy_stream_h,proc_lib_hack,3,[{file,"e:/_dev/news/_build/default/lib/cowboy/src/cowboy_stream_h.erl" },{line,158}]},{proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,247}]}]

但是当我像这样使用 echo 时：

echo(Echo, Req) ->
    cowboy_req:reply(200, #{<<"content-type">> => <<"text/plain; charset=utf-8">>}, Echo, Req)
        end.

我收到请求 - ({"action":"insert","key":"some_key", "value":[1,2,3]})

所以似乎 ETS 有问题？但我不知道我在哪里搞砸了

在其他模块中创建 ets

ets:new(news, [ordered_set, protected, named_table, {keypos,1}, {read_concurrency, true}, {write_concurrency, true}])

您能否告诉我解决此问题的正确方向

Answer 1

ets:new 调用中的protected 选项意味着只有创建 ETS 表的进程才被允许访问insert 数据。其他进程只能读取数据。

改用public，所有进程都将拥有读/写访问权限。