This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
Servlet containers use special classloaders for JSPs so that they can be replaced with new versions without restarting anything. A change to se rvlet requires a restart of the web application, but not the server.
The details of how to restart individual web apps are specific to the servlet container. For example, Tomcat has the Manager web app (generally at http://localhost:8080/manager/html) that allows you to do this.