shadowJar plugin help

I’m using com.github.johnrengelman.shadow for create ShadowJar.
My expectation is that, inside my generated jar file, there are all library with jar format.
Let say, inside my jar, there are “commons-io.jar, common-lang.jar…” instead of the .class files copied from .jar file.

I can’t find any help from the document of johnrengelman.shadow plugin.
How to do it with this plugin, or do you have any other plugin can do that?
I’m using JDK 1.8