Existing SOAP service and new Angular Web App

We have an established WCF SOAP service. Its interface is defined in WSDL, from which C# classes are generated for our server (customers generate client-side bindings in various languages, from the same WSDL). The WSDL has a current version, which we can change a bit, and old versions, which we can't change or drop without a deprecation period, consultation etc. The SOAP requests tend to be complicated, having multiple XML namespaces within the same request.

The WCF SOAP service has a lot of "smarts" in it, and provides exactly the kinds of fetching and reporting facilities that we need for a new Web application that we need to make. We hope to use AngularJS for the client side of that. But these complex SOAP requests aren't easy to make in JavaScript world. If only we had a REST service, we could use angular Resource service. If not that, then a server that spoke JSON, albeit in an RPC style like SOAP, would run a fairly close second.

I've had various ideas for how the impedance mismatch between our server and client might be mitigated. But nothing sounds quick or easy.

I've thought of: -

  1. Write a new REST service. Exactly what the client-side wants, but a serious piece of new development.
  2. WebHttpBinding looks to offer something. But seems to me like it requires C# markup of custom attribute (how to achieve when our C# is generated from WSDL) and possibly wouldn't support our complex types
  3. Obtain or write loads of client-side JS to abstract away calling SOAP services. But, unless this can be auto-generated from the WSDL, it's a huge amount of client-side code to write.
  4. Write an IDispatchMessageFormatter for the server, to accept some JSON format of messages that I invent. Sounds hard, especially as good examples of people implementing and integrating IDispatchMessageFormatter seem hard to come by.
  5. Write a MessageEncoder to swap between JSON and XML. But this isn't really an encoding operation, as became very clear when I tried to write it!

I'm searching for suggestions.

Generally, I recommend a REST service for any AngularJS development and have wrapped a number of legacy systems with Node.js API servers. Of course there is a massive amount of "it depends", but generally most projects will be happier and more productive following that route.

Some Things To Think About

  1. How well does your current SOAP API fit the user interface requirements?
  2. Are you experienced with Express, Sinatra, Flask or other micro-framework that allow rapid development of REST APIs? I find I can build a solid Node.js Express API server in a couple of hours and then extend it as I build the AngularJS application out.
  3. How experienced are you with AngularJS? It's a more advanced project to build a complex data layer client-side.

Six Reasons Why REST is Important for AngularJS

  1. It's much faster to write Angular code using $resource and $http. Get the API right is a good recommendation for effective AngularJS development. Indeed, you could argue that AngularJS is designed for REST, and that's why plain JavaScript works for the model (see 2).
  2. Angular's plain-old JavaScript object data model works well with a REST API that speaks JSON that matches the user interface. However, issues arise when there isn't a good fit- Angular doesn't have a formal data model so you end up writing an lot of code trying to rationalize your API to work well with Angular. 3rd party libraries like breeze.js may offer some solution, but it's still awkward.
  3. You can scale easily with caching. It's easy to add Redis or memcache or Varnish or other common HTTP caching solutions into the mix. Resource-based abstractions are perfect for caching strategies due to the transparency and idempotency of a REST api.
  4. Loose coupling of front-end and server- it will be easier to support changes to the backend if you migrate off SOAP or need to integrate with other services.
  5. It's generally easier to test JSON APIs separately from AngularJS logic, so your test suites will be simpler and more effective.
  6. Your new REST API will be easier to leverage for future AngularJS and JSON-oriented projects.

I hope that helps.

Cheers, Nick