Discovering the application's path

Hello,

I whould like do discover the path of my application, so plugins, xml dtd files and other stuff like that could be grouped only in this directory. Do you know how to do that?

I actually have a solution, but it look to complex and a little bit error prone... specially if the application is inside a JAR. (In this case, i whould like to discover the jar path, not the path of the main class inside the jar).

Any suggestions will be welcome. Thanks in advance.