How to patch a web application

Hello,
I'm working on a web application and was wondering should there arise a need to patch the application's UI or the back-end (i.e. Java classes) in future is it possible to do it without have to go through the process of rebuilding/recompiling and deploying the complete package.
Not sure what other specifics to post. If you have questions please ask and I'll revert with the information.

Any suggestions/ ideas are welcome.

Thank You

I alway go through a complete rebuild and redeployment because it's the only way to keep a proper handle on exactly what is deployed.

Thought so because Java needs to be compiled (to establish the class links for dependencies) and not interpreted like PHP or other languages.
Thanks for the quick reply Bear.

If you can foresee that one or more particular classes are going to change more often than you want to deploy, you could run those as one or more OSGI bundle as part of an embedded OSGI container.

Thanks for the suggestion Ulf. Never worked with the OSGI. Could you point me in the right direction to start?

Some introductory material is at http://www.coderanch.com/how-to/java/OSGiLinks. Apache Felix is a good OSGi container; its Karaf subproject is made for embedding.

Many thanks Ulf.