Keep JNLP unsigned and allow <all-permissions/>

I have made a small java swing application that I want to share with a friend of mine. My application accesses the user's file tree and then writes a file and places it on the user's drive.

Right now I am testing the jnlp on my laptop and the error i am getting is this: Found unsigned entry in resource

I have added these lines to my .jnlp

<security>开发者_如何学Python
    <all-permissions/>
 </security>

I understand that have to add signed code but that has no use to me since the application is only between me and my friend. This guy here has done something like a fake signing.

How can I do that? How exactly is code signed?

How exactly is code signed?

Here is an example. The filetest.zip contains build.xml, source & JNLP. The build file demonstrates how to sign the code with a self-signed certificate.