How to do http POST in Mathematica?

Question

The Import command lets you do a HTTP GET from a URL, like this

Import @ "http://merkosoncampus.com/wp-content/uploads/2011/05/higgs-boson.jpg"

This sends an HTTP GET request to the server and presumably parses the response according to some rules for inferring the type of data, from the content or from the extension ".jpg" or whatever.

Listening on the socket, we see something like this

GET http://merkosoncampus.com/wp-content/uploads/2011/05/higgs-boson.jpg HTTP/1.1
User-agent: Mathematica/8.0.4.0.0 PM/1.3.1
Host: merkosoncampus.com
Proxy-Connection: Keep-Alive

whereas what I want is something along the lines of

POST http://foo.bar.com/myService HTTP/1.1
User-Agent: Mathematica/8.0.4.0.0 PM/1.3.1
Host: foo.bar.com
Accept: */*
Connection: Keep-Alive
Content-Length: 76
Content-Type: application/x-www-form-urlencoded

{ "myJsonStuff" : {"number" : 1} }

I looked for options in Import, praying for something like Method->"POST", but didn't find anything useful.

I'd be grateful for clues, experience, ideas, sample code. In the mean time, I intend to work around it by writing my desired JSON to a file and using curl to POST it, but it's way sub-optimal.

Answer 1

In a post about automated image uploading Arnoud Buzing describes an undocumented and unsupported POST method. It looks like this:

 xml = Import[url, "XML", "RequestMethod" -> "POST", 
              "RequestParameters" -> {"key" -> key, "image" -> image}];

Note: at the time of this answer I was using V8. Since the arrival of URLFetch in V9 I believe URLFetch is the preferred method.

Answer 2

Use URLFetch in Mathematica 9.0.1.

Answer 3

Using the great example of Szabolcs from here, I implemented the following little function that solves my problem. You must give it a List of Rules, and it will send them to the hard-coded web-service endpoint inside. To test it, I implemented a little NodeJs server that reads the JSON body of a POST request, parses it, unparses it, and sends it back. So this is just a very expensive way of converting rules into JSON in MMA, checking their syntax in Node.Js, and sending them back to MMA to be decoded back into native rules.

bounceRules[requestRules_] :=
 Module[{
   requestJsonString,
   url, client, method,
   entity, responseCode, response,
   responseRules, responseExpression},
  JavaBlock[
   requestJsonString = ExportString[requestRules, "JSON"];
   url = "http://127.0.0.1:5000/bounce";
   client = JavaNew[
     "org.apache.commons.httpclient.HttpClient"];
   method = JavaNew[
     "org.apache.commons.httpclient.methods.PostMethod", url];
   entity = JavaNew[
     "org.apache.commons.httpclient.methods.StringRequestEntity",
     jsonString];
   method@setRequestEntity[entity];
   responseCode = client@executeMethod[method];
   If[responseCode === 200,
    (* then *)
    response = method@getResponseBodyAsString[];
    responseRules = ImportString[response, "JSON"];
    (* else *)
    Message[
     bounceRules::httperr,
     responseCode];
    $Failed
    ]]]

My main hangup, btw, was due to the fact that http://localhost inexplicably does not work. I get timeouts and exceptions and all manner of opaque torture from the java stack. Once I switched to http://127.0.0.1 everything just worked.