I\'m having this weird problem making my project Maven-based. I created a new Maven project in Eclipse and enabled the Dynamic Web facets. But during runtim
If you look into your deployment and see that WEB-Inf/lib is empty of your Maven dependencies, then ensuring those Maven dependencies are in your deployment assembly is crucial as mention in the chosen answer.
However be wary of Eclipse then not refreshing everything even with a Maven update. If you clean, rebuild and redeploy and still do not see the lib folder being populated try removing and re-adding the application to the server deployments via Servers>Add and Remove.
This unclogged the system for me.