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This question was posted on the Adobe ColdFusion forums (found here at http://forums.adobe.com/thread/546708?tstart=0).

Does anyone know of a service for this compatible with CF? I need to display an amount for Korean Won and USD on a checkout form and the service at http://www.xmethods.net/sd/2001/CurrencyExchangeService.wsdl doesn’t exist anymore. I searched Google for a while but didn’t find much. Thanks!

The issue was in understanding how to read a raw WSDL (Web Service Description Language) document. I’ll be the first to admit that these can be a bit daunting, but after you know a little about how they are typically structured, you can surmise what methods and their arguments are available to you.

The WSDL in question can be found here at http://www.webservicex.net/CurrencyConvertor.asmx?WSDL. Go ahead and open that and take a look. The first thing we can see about this document is at the top with the tag declaration. Inside here we see an element declaration (as seen by the tag) named ConversionRate. This is a clue into what methods may be available.

To be certain you want to find definitions. These are the actual methods that are defined in the service. Looking at this document we can see three distinct methods: CurrencyConvertorSoap, CurrencyConvertorHttpGet, and CurrencyConvertorHttpPost. All of these methods have the same name, “ConversionRate”. This is seen by looking at the tag under the tag.

The reason for three methods with the same operation name becomes more apparent when we go down and examine the tags. These tags actually specify the details of HOW a given method can be called. You’ll notice that there are three bindings (actually there are four, but one is for a different SOAP binding) here. One for SOAP, POST, and GET. Each of those points to the appropriate portTypes that we saw above. How can we tell? Take a look at the “type” attribute on the tag. It will point to the portType definitions above.

Ok, that’s cool. So we know what methods are available, but how do we know what arguments to pass to these methods? Let’s take a look at the SOAP method version of “ConversionRate”. At the bottom of that definition you will see and tags. These specify what inputs and outputs are expected. Input is what we wish to look at first.

In this method the tag contains a message attribute with the value of “tns:ConversionRateSoapIn”. This tells the service that the input, or arguments, expected are defined in the “ConversionRateSoapIn” element. Scroll up just a tad and you will see it’s definition in the tag that has a name attribute of “ConversionRateSoapIn”. To get more confusing, this contains a tag named with an “element” attribute of “tns:ConversionRate”. Remember that element tag we talked about at first? That is what this attribute is referring to. Go ahead and take a look at that.

The “ConversionRate” element is a complex type, which is a sequence of arguments. There are two actually: FromCurrency, and ToCurrency. Sweet, there are our arguments. Notice also that their type is “tns:Currency”. That is actually just below this element and looks like ““. This is actually a list of valid values for our arguments FromCurrency and ToCurrency.

Great, so that’s a lot of work. Welcome to the world of Web Services! Now let’s look at a small snippet of ColdFusion code that actually uses this service!

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<cfset service = createObject("webservice", "http://www.webservicex.net/CurrencyConvertor.asmx?WSDL") />
 
<cfset fromCurrency = "AUD" />
<cfset toCurrency = "USD" />
 
<cfset result = service.ConversionRate(fromCurrency, toCurrency) />
<cfdump var="#result#" />

Woah, that was easy! Just create the object as a type of “webservice”, give it the URL to the WSDL, and call the method “ConversionRate” and pass in two strings. Here we are getting the conversion rate from Australia currency to American USD.

I hope this sheds a LITTLE light on the loveliness that is WSDL documents. Happy coding!

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Filed under:
ColdFusion, Development by Adam Presley