使用Java修改jar文件中的xml文件

I currently am tasked with updating an XML file (persistance.xml) within a jar at a customers site. I can of course unjar the file, update the xml, then rejar the file for redeployment. I would like to kind these command line operations in a Swing App so that the person doing it does not have to drop to the command line. Any thoughts on a way to do this programatically? I currently am tasked with updating an XML file