Code Signing *.jars using DoD PKI Hard token

maybe of interest - see "Java Keystore". it uses jarsigner and pfx to sign .jar file. however, CAC (or smart card) is not supposed to have private key exported hence you will not have pfx.  

http://www.ewert-technologies.ca/blog/articles/cross-platform-code-signing

challenge is how to create and link the keystore used for signing to CAC.
there is an old article series (see pg1,2 and 3)  on smart card in general using pkcs#11 which you should take a look first for general smartcard

Pg1-http://www.developer.com/java/other/article.php/3587361/Java-Applet-for-Signing-with-a-Smart-Card.htm
Pg2-http://www.developer.com/java/other/article.php/10936_3587361_2/Java-Applet-for-Signing-with-a-Smart-Card.htm
pg3-http://www.developer.com/java/other/article.php/10936_3587361_3/Java-Applet-for-Signing-with-a-Smart-Card.htm

Specifically the pkcs#11 is using Sun java library seems to be the common way for java. Closest I can find for such java codes (2 links) to CAC are stated below which can be useful ref.

//Create our certificates from our CAC Card
         String configName = "card.config";
         Provider p = new sun.security.pkcs11.SunPKCS11(configName);
         Security.addProvider(p);

http://stackoverflow.com/questions/752890/how-to-connect-to-https-server-using-common-access-card/753129#753129

http://stackoverflow.com/questions/544056/common-access-card-cac-authentication-using-java

You can check this out this section "Signing and Verification with the On-Card Certificate" for the signing as well, but it will be rather similar as above (pg1-3) links

http://rostislav-matl.blogspot.sg/2012/04/using-smart-card-as-keystore-in-java.html

Hope it helps...Personally never done that ....