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<  Advanced Erlang/OTP  ~  HTTP POST Capability
seancharles
Posted: Thu Nov 01, 2007 8:39 am Reply with quote
User Joined: 18 Jul 2007 Posts: 57
What is the *easiest* and *cleanest* (i.e. minimum code) to do a simple HTTP POST to a URl with parameters and get back the response ?

I have looked at the yaws code, ibrowse code but my lack of Erlang experience has left me none the wiser on how to do what I want to do.

I am trying to interface to an SMS service in Erlang, having done it in Coldfusion for the day job I thought I would write a comparison so *they* can know that I was right when I said we should use Erlang.

Coldfusion is a lobotomy one keysroke (plus numerous angle brackets) at a time. Sad

Can anybody shed some light, docs to read, examples etc etc

Thanks
Sean Charles
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seancharles
Posted: Sun Nov 04, 2007 10:03 pm Reply with quote
User Joined: 18 Jul 2007 Posts: 57
OK, regarding this thread: http://www.trapexit.org/forum/viewtopic.php?p=33038 where it was rumored that ibrowse:send_req could do a POST, the thread hinted at the README in 1.2.9.

I read the README and there is *NO* example of a POST to be found anywhere. So, after sniffing the code and thinking about it I came up with this example:
Code:

-module(itest).
-compile([export_all]).

go()->
    ibrowse:start(),

    ibrowse:send_req(
      "http://?????????.com/win/tests/posttest.cfm",
      [{"Content-Type","application/x-www-form-urlencoded"}],
      post,
      "X=1&y=2&z=3333"
      ).

It didn't work against a Coldfusion server unless you add the application/x-www.... and the final string should be URL encoded as the server would expect, all of which is standard HTTP expectation!
Code:

Output, run from erlang-shell in EMACS:

itest:go().
{ok,"200",
    [{"Date","Sun, 04 Nov 2007 21:54:09 GMT"},
     {"Server","Apache/2.0.54 (Linux/SUSE)"},
     {"Set-Cookie","CFID=108909;expires=Tue, 27-Oct-2037 21:54:09 GMT;path=/"},
     {"Set-Cookie",
      "CFTOKEN=62929827;expires=Tue, 27-Oct-2037 21:54:09 GMT;path=/"},
     {"Transfer-Encoding","chunked"},
     {"Content-Type","text/html; charset=UTF-8"}],
    "[ECHO:X = 1]<br/> [ECHO:Y = 2]<br/> [ECHO:Z = 3333]<br/> "}

And for completeness, the little bit of Coldfusion that I posted to:
Code:

<!--- Echo back the post parameters --->
<cfif lcase(cgi.request_method) eq  "post">
<cftry>
   <cfloop list="#form.fieldnames#" index="f">
   <cfoutput>[ECHO:#f# = #form[f]#]<br/></cfoutput>
   </cfloop>
   <cfcatch type="any">
      <cfoutput>:#cfcatch.Message#</cfoutput>
   </cfcatch>
</cftry>
<cfelse>
GET was used.
</cfif>

There is plenty of code to do that laying around the place.

Now that I have the ability to POST I will play a little more and see what other styles the Body() part of send_req can process, I tried lists of variables but it bombed on me, that is,
Code:
[{x,1},{y,2},{z,3}]
results in the message:
Code:
Bad value on output port 'tcp_inet'

{error,send_failed}


Keep on trying.... Smile
So, cool, I answered my own question, learned a lot more in the process, which is what it's all about, and I know I like Erlang more and more with each passing day!
(Sad git) We love it! LOL
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Kenneth
Posted: Sun Nov 11, 2007 9:17 pm Reply with quote
Joined: 28 Feb 2005 Posts: 5 Location: Stockholm, Sweden
[quote="seancharles"]OK, regarding this thread: http://www.trapexit.org/forum/viewtopic.php?p=33038 where it was rumored that ibrowse:send_req could do a POST, the thread hinted at the README in 1.2.9.

Hi ,

Why not use the http client in the Erlang/OTP distribution, it can definately do a POST, see the
documentation here:
http://www.erlang.org/doc/man/http.html

Kenneth Erlang/OTP team at Ericsson
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seancharles
Posted: Sun Nov 11, 2007 10:18 pm Reply with quote
User Joined: 18 Jul 2007 Posts: 57
Embarassed My shiny new copy of Programming Erlang should be arriving tomorrow.
Why oh why oh why oh why did I fail to see this at all!!!
Laughing
Oh my god!
Should I even continue.....

Thanks for that.
Sean.
Smile
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seancharles
Posted: Mon Nov 12, 2007 7:25 pm Reply with quote
User Joined: 18 Jul 2007 Posts: 57
An example of a POST using the standard 'http' request method seemed to be in order after my appallingly bad job of reading the documentation!
Code:

-module(echo).
-export([pt/0]).


pt() ->
    http:request(
      post,
      {
        "http://scream-it.com/win/tests/posttest.cfm",
        [],
        "application/x-www-form-urlencoded",
        "x=2&y=3&msg=Hello%20World"
       },
      [],
      []
     ).

This does the same as my other example using the ibrowse module, producing the following output from the same little Coldfusion script:
Code:

{ok,{{"HTTP/1.1",200,"OK"},
     [{"connection","Keep-Alive"},
      {"date","Mon, 12 Nov 2007 19:08:52 GMT"},
      {"server","Apache/2.0.54 (Linux/SUSE)"},
      {"content-length","66"},
      {"content-type","text/html; charset=UTF-8"},
      {"set-cookie",
       "CFID=141882;expires=Wed, 04-Nov-2037 19:08:52 GMT;path=/"},
      {"set-cookie",
       "CFTOKEN=19286971;expires=Wed, 04-Nov-2037 19:08:52 GMT;path=/"},
      {"keep-alive","timeout=15, max=100"}],
     "[ECHO:X = 2]<br/> [ECHO:Y = 3]<br/> [ECHO:MSG = Hello World]<br/> "}}

I hope my Joe book turns up tomorrow!

Smile
Thanks everybody.
Sean Charles.
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