REST API implementation using Yaws - yaws

Question

I'm trying to build a REST API using the Yaws web server but I'm unable to get Yaws to dispatch requests to my module.
-module(rest).
-include_lib("stdlib/include/qlc.hrl").
-include_lib("yaws/include/yaws_api.hrl").
-export([out/1, addAirport/4, handle/2]).
-compile(export_all).
-define(RECORD_TYPE, airport).
-define(RECORD_KEY_FIELD, code).
-record(airport,
{code, city, country, name }).
start() ->
application:start(mnesia).
do_this_once() ->
mnesia:create_table(airport, [{attributes,record_info(fields,airport)},{index, [country]}]),
mnesia:stop().
out(Arg) ->
Method = method(Arg) ,
io:format("~p:~p ~p Request ~n", [?MODULE, ?LINE, Method]),
handle(Method, Arg).
method(Arg) ->
Rec = Arg#arg.req,
Rec#http_request.method.
convert_to_json(Lines) ->
Data = [{obj, [{airport, Line#?RECORD_TYPE.code},
{city, Line#?RECORD_TYPE.city},
{country, Line#?RECORD_TYPE.country},
{name, Line#?RECORD_TYPE.name}]} || Line <- Lines],
JsonData = {obj, [{data, Data}]},
rfc4627:encode(JsonData).
addAirport(Code, City, Country, Name) ->
NewRec = #?RECORD_TYPE{?RECORD_KEY_FIELD = Code,
city = City,
country = Country,
name = Name},
io:format("~p:~p Adding Airport ~p~n",
[?MODULE,?LINE, NewRec]),
Add = fun() ->
mnesia:write(NewRec)
end,
{atomic, _Rec} = mnesia:transaction(Add),
NewRec.
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};
handle('POST', Arg) ->
{ok, Json, _} = rfc4627:decode(Arg#arg.clidata),
io:format("~n~p:~p POST request ~p~n",
[?MODULE, ?LINE, Json]),
Airport = rfc4627:get_field(Json, "airport", <<>>),
City = rfc4627:get_field(Json, "city", <<>>),
Country = rfc4627:get_field(Json, "country", <<>>),
Name= rfc4627:get_field(Json, "name", <<>>),
_Status = addAirport(Airport, City, Country, Name),
[{status, 201},
{html, Arg#arg.clidata}];
handle('PUT', Arg) ->
[IndexValue,_] = string:tokens(Arg#arg.pathinfo),
{ok, Json, _} = rfc4627:decode(Arg#arg.clidata),
io:format("~p:~p PUT request ~p ~p~n",
[?MODULE, ?LINE, IndexValue, Json]),
Airport = rfc4627:get_field(Json, "airport", <<>>),
City = rfc4627:get_field(Json, "city", <<>>),
Country = rfc4627:get_field(Json, "country", <<>>),
Name= rfc4627:get_field(Json, "name", <<>>),
NewRec = #?RECORD_TYPE{
?RECORD_KEY_FIELD = Airport,
city = City,
country = Country,
name = Name},
io:format("~p:~p Renaming ~p",
[?MODULE, ?LINE, NewRec]),
ChangeName = fun() ->
mnesia:delete(
{?RECORD_KEY_FIELD, IndexValue}),
mnesia:write(NewRec)
end,
{atomic, _Rec} = mnesia:transaction(ChangeName),
[{status, 200},
{html, IndexValue}];
handle('DELETE', Arg) ->
[IndexValue, _ ] = string:tokens(Arg#arg.pathinfo),
io:format("~p:~p DELETE request ~p",
[?MODULE, ?LINE, IndexValue]),
Delete = fun() ->
mnesia:delete(
{?RECORD_KEY_FIELD, IndexValue})
end,
Resp = mnesia:transaction(Delete),
case Resp of
{atomic, ok} ->
[{status, 204}];
{_, Error} ->
io:format("~p:~p Error ~p ",
[?MODULE, ?LINE, Error]),
[{status, 400},
{html, Error}]
end;
handle(Method,_) ->
[{error, "Unknown method " ++ Method},
{status, 405},
{header, "Allow: GET, HEAD, POST, PUT, DELETE"}
].
do(Q)->
F = fun() ->
qlc:e(Q)
end,
{atomic, Value} = mnesia:transaction(F),
Value.

Answer 1

You need to register your module as a Yaws appmod in the server configuration portion of your yaws.conf file. Please see the Yaws appmod documentation for the necessary details.