War file updates existing files?

[Raj Puri]

Does a war file updates existing files and adds/deletes new in there. I have a war file called sales.war. Now I need to redply the application we done a number of changes. If I copy new war file in webapps will it update all folders correctly under there or I need to delete war file and delete all directory and start first. I have srvlets in my application I believe servlet has url mapping that got created by war file automatically, what will happen to those? Will it corect all componenets of web application correctly if I just copy new war and restart the server.