How to sign a jar to never expire?

Question

I used jarsigner to sign my jar file. But I got a warning:

Warning:
This jar contains entries whose signer certificate will expire within six months.

How can I make it never expire or expire in a longer time?

Answer 1

Specify the required number of days in the -validity parameter to keytool.

Addendum: -validity is an option to keytool.

keytool -genkey -alias sawyer -validity 1234 -dname "…"

After you create the new key, use its unique alias with jarsigner to sign your JAR.