Need help with importing 3rd party libraries

Hello All!

I have a task at hand to validate that response json conforms to a specific json schema. From what I've read, I have to use a 3rd party library to make validation happen and place it in the .../bin/ext folder. The library I found is groovy-json-schema (on GitHub). I've downloaded it, compiled it and made a jar file out of the resulting .class files. Then, I have placed that jar file in the /bin/ext folder and restarted soapUI. Based on the logs, my jar has been loaded, but my attempts to "import com.lumata.os.groovy.jsonschema.JsonSchema" class are failing every time.

My setup is as follows: soapUI Pro 4.5.1 (I know I should be posting this in the pro forums, but I'm still waiting for my manager to get me the pro forum credentials)
OS: Mac OS X (10.7.5)

Folders I have tried to place my jar file in:

/Applications/SmartBear/soapUI-Pro-4.5.1.app/Contents/Resources/app/bin/ext
/Applications/SmartBear/soapUI-Pro-4.5.1.app/Contents/Resources/app/lib
/Applications/SmartBear/soapUI-Pro-4.5.1.app/Contents/Resources/app/bin

In case this matters, here is how I got my jar file:

mvn compile
jar -cf myfile.jar *.class

All these locations would load the library, but not allow classes to be imported.

Any help/guidance is appreciated.

Thanks.