Originally posted by Anthony Smith: Is this currently possible? Could I update one jar file w/o shutting down? Could I change log preferences w/o shutting down? Can I remove or stop one webapp w/o shutting down?
A lot depends on your Tomcat configuration, but...
Yes, you can deploy without shutting down. There can be issues - for instance, I've seen where if the WAR file you are copying into the webapps directory is very large, tomcat can start deploying before the whole thing is there.
You can replace a jar in a deployed application's WEB-INF/lib directory and using the manager, reload the application.
Dunno about the logs.
You can deal with individual applications through Tomcat's manager (assuming you configured a manager user in the tomcat-users.xml file).
With log4j, you can change preferences in the log4j.properties file. I put this in the conf directory for tomcat. If you use the method PropertyConfigurator.configureAndWatch(), changes will take effect without even restarting the app.