Want the name of the file loaded into DataSource.

I did find the filename. I get it from:

testCase.getTestStepByName("DataSource").datasource.filename

Part of my confusion arose because the class involved, ExcelDataSource, is not included in the javadocs that I found at http://www.soapui.org/apidocs/index.html
Is there a better url I should use? Did some packages get intentionally left out of the docs?

Now that I've found it, I note that there's a setter for the filname. Any chance you could tell me how to use it? I tried just setting the filename, but the it didn't seem to work. There are other methods in that class, like load() for example, that are possibly needed after setting the filename, but I dunno.

Cheers,
--Bob