Using Third-Party Generated Certificates in HTTPRequest Calls

I've been doing various integrations with external web services lately and have learned some things along the way. The latest integration I did required two-way authentication.  The Salesforce documentation makes some assumptions about these integrations-

1. That the service you're integrating with provides a parseable WSDL.
2. That the service you're integrating with allows you to upload a signed certificate that was generated from Salesforce for the two-way integration.

And if both of those hold true, the Salesforce documentation (and various related blog posts) will be sufficient for you.  However-

1. Not all services provide a WSDL, and even those that do might include XML elements that are not supported by Salesforce.  In this case, you're on your own for writing an Apex class to interact with the web service.
2. Some services provide a WSDL that Salesforce can parse, but you'll find that you need to edit the resulting Apex class to include properties that were excluded.  Though I didn't dig in to see if this was the fault of the WSDL file itself or the parser, I suspect the latter.  How to go about editing that generated Apex class is worth it's own post.
3. Some services provide you with a client certificate file that you need to include in your request- you don't have the option of generating one in Salesforce and getting it signed.

None of these are insurmountable, but they'll take a lot more leg-work on your part and in the case of having to provide a third-party generated client certificate in an HTTP request, I found myself having to piece together how to do so from various forum posts.  So I'll focus on that today.  

So an external service (in my case, the credit card processor First Data) provides you with a client certificate file and a password for that file.  Now what?  In Salesforce's documentation for the HTTPRequest class you'll notice a method called "setClientCertificate" with a note that this method is deprecated and you should really use "setClientCertificateName".  But if you've been provided with the client certificate, "setClientCertificate" is what you'll need.  Here's how to get it to work-

• Upload the client certificate as a Static Resource
• In Apex, query for that file and base64 encode the body of the file into a string variable.
• In your HTTPRequest variable, use the setClientCertificate method with the base64 encoded certificate as the first argument, and the certificate password as the second argument.

Oh sure, it's easy when you know how to do it.  And a note that alternatively, you can base64 encode the certificate yourself and use the resulting string in setClientCertificate, but the above seemed a little more elegant.  The actual code to accomplish this-

String cert;

for (StaticResource sr : [Select Id, Body from StaticResource where Name =: <certfilename>]){

cert = EncodingUtil.base64Encode(sr.Body);

}

HttpRequest hReq = new HttpRequest();

hReq.setEndpoint(<url>);

hReq.setMethod('POST');

hReq.setClientCertificate(cert, <certpassword>);

If you were lucky enough to have a WSDL that Salesforce was able to parse, you'll be setting the "clientCert_x" variable of the stub to the base64 encoded string and the "clientCertPasswd_x" variable to the password.

Once again, hope this saves someone some time!