Develop a Soap service in elixir and phoenix

If you can, build a REST-to-SOAP service in a language that has good SOAP support. I have tried all of the various SOAP libraries in Erlang and Elixir and have yet to find one that can properly parse the WSDLs that I had to deal with (they all failed at some point or another)

I ended up using Ruby with soap4r (well, soap4r-ng), because neither savon nor lolsoap could handle the complexity of the SOAP service I used.

SOAP is a nasty piece of work because it’s fully object oriented and if your service was built system-first, rather than WSDL-first, you will have heavy object orientation and polymorphism to deal with and pretty much all of the Erlang/Elixir SOAP services that I played with failed.

If I have to deal with another SOAP service (I’m usually doing enterprise integrations, so it’s not unlikely), I will either do the same thing or build my own WSDL/WSSE/SOAP layer with the goal of open sourcing it, but that’s probably a year in the future at least. It’s a hard thing, because once we got started with the soap4r approach, we had our gateway and Elixir code implemented in about two weeks. It would have taken two weeks just to get a working WSDL parser for Elixir to handle the multiple WSDLs I had to deal with.

I love Elixir, but there’s no good answer to doing SOAP in Elixir at this point.

Thanks Austin for sharing your experience. My requirement is SOAP service only in Elixir. I have only 1 WSDL which I have to work on.
I referrred to the below link for implementation but the tutorial is not so good:-

https://github.com/elixir-soap/soap

I understand. You might have success with one of the various projects I list below, but it entirely depends on whether the WSDL represents something that was written and the service code was written from it…or whether the WSDL is something generated from the service code. The former presents interfaces that conform to spec far more frequently and simply. The latter will do things that are possible in the spec, but don’t happen in WSDL-first services, which means that most WSDL parsers handle them poorly.

Here are all the toolkits I’ve tried before basically punting:

• elixir-soap/soap
• trbngr/Lyex
• polyfox/castile
• bet365/soap
• zdeneksejcek/soapex

Of these, bet365/soap is the most mature but hasn’t been maintained in years; polyfox/castile is promising but hasn’t been maintained in a long time; zdeneksejcek/soapex is really interesting but incomplete. None of them worked with any one of the four WSDLs I had to work with.

If yours is a simple enough service, you’d probably be better off building EEx templates for sending the requests and XML parsers for receiving the requests and calling the services with an HTTP client (most SOAP is over HTTPS, after all).

If it’s not a simple service…all I can say is good luck doing it in Elixir. SOAP is a technology that only works really well if you have relatively large engineering teams building the code tooling around the excessively complicated standards. The absolute best platforms/languages to develop SOAP services and clients are Java and C#—because the SOAP standards were mostly written by people who work at Oracle (and Sun before that), IBM, SAP, and Microsoft.

The truth is, I don’t want to write a SOAP client in Elixir—because I don’t want to use SOAP if I can avoid it, and that disdain also means that I’m not likely to maintain it (even the Ruby toolkit that I ended up using, soap4r-ng, hasn’t been maintained in a few years, but it’s a lot more mature than anything in Elixir/Erlang that does SOAP).

Good summary. I’d question OP’s requirement to create SOAP service (of all things!) but they might be stuck with a strong-headed customer.

@rameshsharma Are there not other options? What are you trying to achieve exactly?

Thanks Austin for the detailed summary.
I have a wsdl url mentioned below. I have to develop a soap service to hit the wsdl using a request xml and get a response. Based on the below url can you suggest me the best approach of work.

https://sandbox.ws-idu.tracesmart.co.uk/v5.6/?wsdl

Is there any reference link of the above point mentioned by you:

‘‘If yours is a simple enough service, you’d probably be better off building EEx templates for sending the requests and XML parsers for receiving the requests and calling the services with an HTTP client (most SOAP is over HTTPS, after all).’’

This is based on a quick reading of the WSDL, but I think that it’s simple enough (it isn’t using any polymorphism that I can see, except in arrays) that it should work with pretty much any of the existing toolkits. It is not simple enough that you could reliably make EEx templates without a lot of example payloads.

The EEx template approach is just one where you get a full-change payload and then use EEx template logic, looping, and substitution to build an appropriate XML file for a payload.

Thanks Austin. So I think then I can go for elixir-soap/soap.
I am completely new to SOAP service in Elixir. The documentation below does not clearly state how to send request xml to hit the wsdl and get the response back.

https://github.com/elixir-soap/soap

Is there any reference anywhere?

On hitting the below command in interactive shell, I am getting the below output.

iex:4> {:ok, wsdl} = Soap.init_model(“https://sandbox.ws-idu.tracesmart.co.uk/v5.6/?wsdl”, :url)
{:ok,
%{
complex_types: ,
endpoint: “”,
messages: ,
namespaces: %{},
operations: ,
schema_attributes: %{element_form_default: “”, target_namespace: “urn:idu”},
soap_version: “1.1”,
validation_types: %{}
}}

Not sure why complex_types, operations are all showing .

Don’t neglect erlang libraries for soap handling as well. Soap was more of a big thing back in erlang’s creation days.

But for note, soap is just (mostly) xml in various defined ways, it’s not hard to do it manually with no libraries at all.

Thanks, by erlang library you mean to refer to bet365/soap ??