JAVA - Load Jar File and get File in src

I want to make a Programm which loads Jar Files from a Directory in my Programm. Want I'd like to do: The Loader should load the Jar an should searches for a Yml File in the src Folder of the Jar. When the Yml File was found, the loader should get the content of the File. In the File is the Location of the MainClass of the Addon. With this Location it can create an instance of the MainClass and give it back to my Programm. This is what I want. I searched a lot but nothing helped yet. I hope you can help me.