I haven't come across any issue of just copying the file and allowing it to be redeployed. For instance, using
JBoss, the only time I have had to reboot the server is when I have a dependency on a .jar file that is in the lib directory of the server, and not in the "app". But within an ear or a war they work fine.
That situation of rebooting had to do with which class loader actually loaded the classes from the jar file. And since the jar in the server's lib directory is loaded by a different classloader than the app's .ear or war file class loader, it causes a problem.
But, in the end redeploying just a .war or .ear file should work fine without having to reboot the server.
Mark