Simple SOAP calls over SSL with Ruby

I deal with web services a lot in my day to day, some good, some nightmarish. Having scripts and example code to deal with them makes my job a lot easier. My example last week was a piece of python code that implemented CONNECT to allow you to make SSL encrypted requests across a proxy in Python. I had to write this code because the company I work for exposes it's web services to clients via SSL, and being able to offer example code to leverage our services in multiple languages is a good thing. Not being able to offer example code in a pretty mainstream (in web terms) language is a bad thing.

Therefore I wrote a similar script to last week's example that uses Ruby to post an XMP SOAP envelope request to an SSL secured site over a proxy. For enterprise use in apps expecting to make thousands of SOAP calls a day I would recommend users to build a full SOAP app using SOAP4R or some equivalent framework. However as this is often overkill for smaller apps that simply want to make a few calls to a web service, doing the request manually as a raw HTTP POST to send the SOAP envelope to the service is usually enough, and doesn't obscure the details of what SOAP really is, an HTTP POST request with a rigorously defined XML payload.

As an aside, to build the SOAP envelope for this example I heartily recommend SoapUI, it allows you to open a WSDL for a particular service and easily generate the XML for each SOAP action. It's really good, especially if you build SOAP web services in your day to day job. It's so good, in fact, that as you get more and more used to using it you might find it replacing the test harnesses you inevitably build to test the web services you build.

Back on topic, because we are building the XML as a string we need to inject any parameters for the SOAP call after we have built it. Luckily Ruby lets us replace substrings in strings pretty easily with the .sub! method. I use it to template my SOAP requests with {1} and {2} etc... Also to avoid being stung with content length issues make sure you finalize your XML before creating the headers dictionary so that your Content-Lenght ('Content-Length'=> soap_data.length) is correct. If you don't, the next 2 hours will be wasted while you go round in circles with HTTP errors that don't make too much sense.

Anyway: here's the code, you'll notice that it's a lot shorter that the Python code from last week, this is because the standard library gives you native SSL over Proxy support. Note the call 'http_session.use_ssl = true'.

require 'net/https'
require 'open-uri'

# Create the SOAP Envelope
soap_data = '''
This is where the SOAP xml would be drafted. I use {1} to template value fields.
'''
# normally I'd inject parameters into the SOAP Envelope using a call like:
# soap_data.sub!('{1}', "example string")

# Set Headers
headers = {
  'Content-type'=> 'text/xml; charset=utf-8',
  'SOAPAction'=> '""',
  'User-Agent'=> 'The useragent you wish to use, useful if you ever have to debug at the other end...',
  'Host'=>  'www.securedurl.com',
  'Content-Length'=> soap_data.length
}

#create session object
uri = URI.parse("https://www.securedurl.com")
path = '/WebServiceHome/services/'
proxy = Net::HTTP::Proxy("aproxyserver",8080)
http_session = proxy.new(uri.host, uri.port)
http_session.use_ssl = true

#start the http session
http_session.start { |http|
  # create the request
  req = Net::HTTP::Post.new(path)
  req.basic_auth mip_user, mip_password
  headers.each{|key, val| req.add_field(key, val)}
  # Post the request
  resp, data = http.request(req, soap_data)
  puts 'Code = ' + resp.code
  puts 'Message = ' + resp.message
  resp.each { |key, val| puts key + ' = ' + val }
  puts data
}