The correct way to use Ocamlnet 3 - Http_client.Convenience.http_post

I am trying to use Http_client.Convenience.http_post to make a http post request.

The API is fairly simple:

val http_post : string -> (string * string) list -> string

Does a "POST" request with the given URL and returns the response body. The list contains the parameters send with the POST request.

What I wish to do is to construct a http post request to get the flight information via google flights, explained as part 1 in here: http://www.nohup.in/blog/using-json-google-flights

To maintain the format of the Post request, I took a screenshot as this:

So finally, I construct a Http_client.Convenience.http_post for it:

open Http_client.Convenience;;

let post_para = [("(Request-Line)", "POST /flights/rpc HTTP/1.1");
         ("Host", "www.google.com");
         ("Content-Type", "application/json; charset=utf-8");
         ("X-GWT-Permutation", "0BB89375061712D90759336B50687E78");
         ("X-GWT-Module-Base", "http://www.google.com/flights/static/");
         ("Referer", "http://www.google.com/flights/");
         ("Content-Length", "275");
         ("Cookie", "PREF=ID=2dc218fc830df28d:U=29aaf343dd519bca:FF=0:TM=1307225398:LM=1308065727:GM=1:S=RWC3dYzVvVSpkrlz; NID=52=VTp1QILW1ntPlrkLx7yLUtOYhchNk35G4Lk35KBd7A3lCznVV5glz7lwDoDP2RkjtTJVNZSomv3iffPqiJz4oXfpoph3ljb2eInGOe-FwosvrmSXPpnLkEWxMHIbuaid; S=travel-flights=YFCjkd9M9h3Z_uEqBmgynA");
         ("Pragma", "no-cache");
         ("Cache-Control", "no-cache");
         ("data", "[,[[,\"fs\",\"[,[,[\"SJC\"]\n,\"2012-04-05\",[\"EWR\",\"JFK\",\"LGA\"]\n,\"2012-04-12\"]\n]\n\"]],[,[[,\"b_ca\",\"54\"],[,\"f_ut\",\"search;f=SJC;t=EWR,JFK,LGA;d=2012-04-05;r=2012-04-12\"],[,\"b_lr\",\"11:36\"],[,\"b_lr\",\"1:1528\"],[,\"b_lr\",\"2:1827\"],[,\"b_qu\",\"3\"],[,\"b_qc\",\"1\"]]]]")];;

let search () = try (http_post "http://www.google.com/flights/rpc" post_para) with
    Http_client.Http_error (id, msg) -> msg;;

let _ = print_endline (search());;

When I run it, it just give me the following error html page:

<HTML>
   <HEAD>
     <TITLE>Internal Server Error</TITLE>
   </HEAD>
   <BODY BGCOLOR="#FFFFFF" TEXT="#000000">
     <H1>Internal Server Error</H1>
     <H2>Error 500</H2>
   </BODY>
</HTML>

Can anyone tell me why? What's wrong with my http_post?

Drop this from post_para, it is not an HTTP Header, OCamlnet will send that automatically for you: "(Request-Line)", "POST /flights/rpc HTTP/1.1".

To send the headers and POST data separately you need to set the headers use set_request_header on the http_call object.

Also the Convenience module in OCamlnet will send the data as application/x-www-form-urlencoded, but I think you need the data sent as is. You can do that by using Http_client.post_raw.

来源：https://stackoverflow.com/questions/17047223/the-correct-way-to-use-ocamlnet-3-http-client-convenience-http-post

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