DPS907 notes – Tue Dec 3

More about SOAP XML Web Services. Final exam info.

Attendance at today’s class is optional. Your professor will discuss SOAP XML web services, the plans for the final exam, answer any questions you may have, and help you with programming tasks.

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Final exam info

Written part, and a programming task. More details are on this linked page.

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Web service design styles

There are two web service design styles in wide use today: web API, and SOAP XML. Their characteristics are summarized below, but feel free to learn more about each by starting with their Wikipedia articles, and then moving on to other authoritative learning resources.

Terminology:

The web API style is also known as:

  • Web 2.0
  • Hypermedia-driven web services
  • REST (Representational State Transfer)

The SOAP XML style is also known as:

  • Web services
  • Big web services
  • RPC (web services)

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Web API

A web API faithfully follows the design intent of the web.

From a programmer’s perspective, a web API is accessed at a single endpoint, known as a resource, via a URI. The data returned then guides the user/requestor to additional resources, via URIs.

All requests made to a web API use the HTTP-defined request methods, including GET, POST, PUT, DELETE, OPTIONS, HEAD, and maybe a few others.

The data format that passes between the caller/client and the server is negotiated (using the Accept and Content-Type request headers), but modern web APIs typically use JSON or a variant. 

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SOAP XML

SOAP XML web services use XML messages that conform to the Simple Object Access Protocol (SOAP). While there are many “moving parts” to this style, Visual Studio tooling and the .NET Framework make it fairly easy to implement a simple SOAP XML web service.

From a programmer’s point of view, a SOAP XML web service “server” is created as a single endpoint in a web app. Then, the programmer writes methods for this web service which can be called by remote callers.

In summary, a SOAP XML web service “server” is a single endpoint that exposes methods to callers.

When a method is called (by a remote caller), a SOAP message is posted (i.e. HTTP POST) to the endpoint. The SOAP message includes the name of the method to be called, and argument data if required. The “server” returns a SOAP message that includes the status/success result of the call, and typically return value data.

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What is WCF in Visual Studio and the .NET Framework?

Microsoft’s Windows Communication Foundation (WCF) is a unified API for building service-oriented applications.

WCF can also be considered an identity or marketing name for the namespaces and classes in the .NET Framework that fulfill this role.

For us as programmers, the WCF prefix for a project or item means that we’re creating a SOAP XML web service.

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