Hello pengpeng,
My advice would be to concentrate on basics as of now like
JSP,
Servlet etc. EJB is more complex and needs some time to understand and master.
In case of frameworks, if you are working on some professional project, there will be some framework used. I think the good way to learn it will be on the job if you are a developer.
I have been in J2EE for past several years. And this has helped me.
If you are an architect or technical specialist then may be you can start learning it one by one based on priorities based on popularity, purpose of the framework etc.
If your projects are hobby projects then its tricky. i think good will be if you invest time in knowing little in broad sense about each framework. And then choosing the ones you feel to study or are useful for your application etc.
Hope that helps..
Regards,
Leena