This is not a complete answer, but I will use as an example the JAR of Tide with which I had this problem a few days ago. It is a JNLP executable JAR which is also self-signed and was locked in Java 8.
I am using Windows.
First, open the Control Panel and look for the Java icon:
Click the Java icon and a new screen will open. Once there, go to the "Security" (or "Security") tab and add your website or URL to the list of exceptions:
source
On Mac, you can find something similar to the one above by going to System Preferences. (source)
On Linux, you can add the exception sites to the file ${user.home}/.java/deployment/security/exception.sites
, being an exception site/URL per line. (source)
What is your operating system?
– Victor Stafusa