About your first question, if you "touch" your web.xml file in the WAR exploded dir, then JBoss redeploys that WAR. If using linux, it's easy to do it with the "touch" command; in windows I know there are some free utilities that do this, but don't know where you can get them (a home-made solution would be to edit the web.xml file and force it saving it with Save As command, for example).
About the second question... Well, it does depend on various factors. If you use interfaces to access your common libraries and the interfaces aren't changed, then I think it's possible to modify them without restarting the dependent WARs, but not really sure of how to make this possible. On the other hand, if you don't use interfaces or your interfaces are changed, then the dependent WARs must be redeployed in order to access the new classes/interfaces.
Be advised that I'm not really sure about my answers because they are based on the J2EE spec, the JBoss code I could understand and my experience, so I'm sure someone from JBoss can answer better your questions, but maybe my answers helped you someway...
Hi, Raist.. Thanks for the reply..
BTW, your first answer didn't work for me..
here is my dir structure ==> jboss/server/default/deploy/abc.ear/def.war
when I touched def.war directory nothing happened..
when I touched the web.xml in def.war directory nothing happened..
when I touched abc.ear, nothing happened..
when I touch the application.xml in abc.ear and it obviously redeploy whole applicaition..
Your second question.. What you do mean by using interface for the common lib..?
Can you elavorate your suggestion a bit more detail please..??