Check in Deployment Assembly,
I have the same error, when i generate the war file with the "maven clean install" way and deploy manualy, it works fine, but when i use the runtime enviroment (eclipse) the problems come.
The solution for me (for eclipse IDE) go to: "proyect properties" --> "Deployment Assembly" --> "Add" --> "the jar you need", in my case java "build path entries". Maybe can help a litle!