Java EE really needs connections! Connections to databases, connections to other components...
Resources can help out with that.
Check out my full Java EE 7 playlist to quickly get caught up:
https://www.youtube.com/playlist?list=PLQnvNIEg5crMDvk7G5Z-WJMQNABl6YPM5
I am following Dr. Danny Coward's book, Java EE 7: The Big Picture.
https://www.amazon.ca/Java-EE-7-Big-Picture/dp/0071837345
