The xml file should provide information what is included in the jar file. However it just came to my mind that getResource might not work. I think it works only with physical files. Instead of getResource try getResourceAsStream.
See official documentation
here. The method will return an InputStream which you have to read, not a file. I don't know what you intended to do with the file object so I don't know how much conversion / processing you have to do to get the desired result out of the InputStream.
You should check the return value from getResourceAsStream in your Eclipse debugger. If it is null the resource is not included in your jar (that's why I asked about the build xml file), otherwise you should be able to read it.
Update:
Your code should then look like this (plus the respective import statement).