It is always helpful to use some tomcat plugin in Eclipse for web development. In the other case, you have to manually deploy the servlets/jsp.

Sysdeo/SQLI Eclipse Tomcat Launcher plugin si quite a famous one and can be downloaded from:

EclipseTotale - Sysdeo/SQLI Eclipse Tomcat Launcher Plugin

It will add a menu in the Eclipse IDE for starting, stopping and restarting the tomcat server.