Retrieving jar signature from code

[rockclimber90]

I need to retrieve the signature information of a .jar file. My own
..jar actually (the .jar file I'm running from).

Is there some API that will allow me to retrieve the signature from an
object reference, class name or package name ?

Something like:

signature = SomeClass.GetSignature(this);

I guess what I want to do is the same thing jarsigner -verify -verbose
does but from my code and for my own jar.

Is there any API to do this ? is jarsigner written in JAVA and if so,
is the source code available ?

Thanks in advance
Frank