how to enable hot deploy in tomcat

Question

I can write an ant script that copies updated class files to web-inf\classes in tomcat. But how can I tell Tomcat 7.0 to auto pick up the changed class files from web-inf/classes directory?

I tried setting autoDeploy="true" in tomcat Host configuration server.xml but when a change is detected, Tomcat session is destroyed. Can I easily a substitute eclipse tomcat plugin in Intellij