Some years back, Java by itself was new! then they said
EJB will rule the world, after that, Struts....and to make it safe, they combined
Struts with EJB.
Then came iBatis, with the advent of ORM concepts, Hibernate followed with more power.
Now the same people who said Struts will rule the world, are saying Spring will rule the world
but actually, ruby on rails is gaining importance paralelly too!
It would be good to learn to be adaptive, and try to grasp the basics of Java, J2EE & OOAD with UML, and learn to be adaptive and versatile! Whatever framework comes, is going to exploit the concepts laid down by the underlying programming language! So, make good friends with the concepts and rest will come your way, with less efforts!
Put in design terminology : Program to an interface, not to an implementation