How to enable hot undeployment/redeployment of war files to Tomcat running on Windows
By default when running on Windows operating system Tomcat locks resources meaning that you cannot redeploy or undeploy when the server is running. To prevent this edit %CATALINA_HOME%\conf\context.xml.
Find the root <Context> and add these two attributes:
<Context antiJARLocking="true" antiResourceLocking="true">
You will now be able to copy updated WAR files to your webapps directory and Tomcat will remove the old app and hot deploy your new app, or to simply undeploy webapps which are no longer needed.