- Go to web project properties.
- Deployment Assembly (Left).
- Add > Select project > Select your lib project > Check “Assemble projects into the WEB-INF/lib folder of the web application” if not checked > Finish.
- Java Build Path (Left) > Projects Tab > Add… > Select your lib project > OK
- Java Build Path (Left) > Order and Export Tab > Select your lib project.
- Save
- Now it works.