Too many idle database connections with Tomcat

I recently had problem when there were too many open database connections in Tomcat. Everything was right, but number is far more then is defined in Tomcat resources.
After some investigation, I have found that problem was that datasources were defined in wrong place - conf/context.xml, and when they are defined there, they are picked for every Web application that is defined in this Tomcat instance (including management and utility), therefore you will have all your connections multiplied by number of applications you have.
Fortunately, it is easy to fix by defining resources under conf/Catalina/localhost/ROOT.xml (ROOT if application is defined under root, otherwise, name of your application), in which case, resources will be provided only for specified application.