我想将 mnesia 数据库中的 YAWS 信息转换为网络。 现在我有代码:
-define(RECORD_TYPE, albums).
-define(RECORD_KEY_FIELD, album_id).
-record(?RECORD_TYPE,
{?RECORD_KEY_FIELD, artist_id, album, albumpath, image}).
convert_to_json(Lines) ->
Data = [{obj,
[{id, Line#?RECORD_TYPE.album_id},
{aid, Line#?RECORD_TYPE.artist_id},
{path, Line#?RECORD_TYPE.albumpath},
{image, Line#?RECORD_TYPE.image},
{album, Line#?RECORD_TYPE.album}]}
|| Line <- Lines],
JsonData = {obj, [{data, Data}]},
rfc4627:encode(JsonData).
handle('GET', _Arg) ->
io:format("~n ~p:~p GET Request ~n", [?MODULE, ?LINE]),
Records = do(qlc:q([X || X <- mnesia:table(?RECORD_TYPE)])),
Json = convert_to_json(Records),
io:format("~n ~p:~p GET Request Response ~p ~n", [?MODULE, ?LINE, Json]),
{html, Json}.
do(Q)->
F = fun() ->
qlc:e(Q)
end,
{atomic, Value} = mnesia:transaction(F),
Value.
和 test.yaws 文件:
<html>
<head>
<meta charset="utf-8">
</head>
<body>
<erl>
out(Arg) ->
Method = method(Arg) ,
io:format("~p:~p ~p Request ~n", [?MODULE, ?LINE, Method]),
my_json:handle(Method, Arg).
method(Arg) ->
Rec = Arg#arg.req,
Rec#http_request.method.
</erl>
</body>
</html>
但是我在 YAWS 输出中得到二进制信息:
{"data":[{"id":8,"aid":3,"path":[[47,114,111,111,116,47,101,114,108,97,110,103,47,116,101,115,116,108,105,115,116,47,65,114,116,105,115,116,32,78,117,109,98,101,114,51,47,65,108,98,117,109,32,78,117,109,98,101,114,32,50]],"image":[[102,114,111,110,116,46,106,112,103]],"album":[65,108,98,117,109,32,78,117,109,98,101,114,32,50]},{"id":2,"aid":1,"path":[[47,114,111,111,116,47,101,114,108,97,110,103,47,116,101,115,116,108,105,115,116,47,65,114,116,105,115,116,32,78,117,109,98,101,114,49,47,65,108,98,117,109,32,78,117,109,98,101,114,32,50]],"image":[[99,111,118,101,114,46,112,110,103]],"album":[65,108,98,117,109,32,78,117,109,98,101,114,32,50]},{"id":14,"aid":5,"path":[[47,114,111,111,116,47,101,114,108,97,110,103,47,116,101,115,116,108,105,115,116,47,65,114,116,105,115,116,32,78,117,109,98,101,114,53,47,65,108,98,117,109,32,78,117,109,98,101,114,32,50]],"image":[],"album":[65,108,98,117,109,32,78,117,109,98,101,114,32,50]},{"id":12,"aid":4,"path": ..............
如何将其转换为字符串？
附注抱歉我的英语不好，感谢您的帮助。
最佳答案
Erlang 中的字符串是不明确的，因为有两种方法来表示它们:作为二进制 (<<"foo">>)，或作为整数列表 ("bar"= [$b, $a, $r ])。
您遇到的问题与第二种形式的字符串(整数列表)有关。您使用的 JSON 编码器不知道您提供的列表是否是字符串。
通常 JSON 编码器会决定字符串的特定格式。 jiffy 要求您对字符串使用二进制文件。 mochijson 采用另一种方式，要求您使用元组/原子 ({array, [1, 2, 3]}) 标记数组。
我的猜测是，您正在使用的模块需要字符串的二进制文件(或至少对于大字符串)。
这应该会为您修复输出:
convert_to_json(Lines) ->
Data = [{obj,
[{id, Line#?RECORD_TYPE.album_id},
{aid, Line#?RECORD_TYPE.artist_id},
{path, unicode:characters_to_binary(Line#?RECORD_TYPE.albumpath)},
{image, Line#?RECORD_TYPE.image},
{album, Line#?RECORD_TYPE.album}]}
|| Line <- Lines],
JsonData = {obj, [{data, Data}]},
rfc4627:encode(JsonData).
注意 unicode:characters_to_binary 的使用。这将采用 iolist(用于在文件描述符或套接字上输出的二进制或列表/二进制/整数的列表)并使用 UTF8 编码将其转换为平面二进制(它也假设 utf8 作为输入，所以要小心)。
关于json - Erlang - 转换二进制可读UTF，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/20615939/