Refer the following wiki page.
It says that,
In a normal archive, JBoss will redeploy the application when the archive is updated. To force JBoss to redeploy an exploded application simply update the top level descriptor. (web.xml, application.xml, etc.)
Hope this might be helpful.
I am having the same problem but I am doing it a little different.
Whenever I package the ear file and deploy it as a file. I can delete that file and jboss will undeploy it. No problems here (besides being slow as dog%#$).
Whenever I deploy it as an exploded directory (same exact structure). I cannot delete that directory without shutting down jboss because the classloader appears to be holding onto the supporting library jar files that are included within the ear file. Therefore, jboss will not allow me to undeploy (delete) the exploded directory.
I don't know if this is a bug or not but it sure is a pain.
The solution to redeploy an exploded directory that was pointed out above did not work for me.
I was trying to just touch the application.xml and was observing the "modifed date" on the application.xml in windows explorer would change but the application would never repdeploy. I had to touch (using ant and fileset) the exploded ear directory. This is the only way I could trigger a redeploy while exploded.
I am using 4.04GA on Windblows XP.