The best way to learn????

Question

I am not sure where to post this type of question, so forgive me if this is not an appropriate forum.
I have a BS in Comp Sci and have been working with Java for 4 years. My skills have increased over the years, but I am finding that they are still lacking in the details.
I've looked through books, but find that most of them only scratch the surface. They are fine if you want to know basic syntax, configuration and such.
Recently I have been looking for other employment. The interviewer's questions tend to go into more details about the intricacies of how things work.
I have been working with JPA entities. Pro EJB 3: Java Persistence API (Pro) has been an excellent resource and our application is fully functional. I would think that I had a good handle on how to implement session beans and entity beans. But interviewers don't ask basic questions.
They want to know more about the life cycle of entity beans, session beans, Servlets, etc.. How does each handle threading? How many Servlets can exist in the container? Explain classloader and jvm considerations.
"how do you configure caching for entities?"
"describe the interactions between the container, entity beans and database"
"What are the different ways of instantiating a String and how are they different?"
"Which class would you override to change a default behavior of Struts?"
I've gone to Borders to try to find a good all around resource, but haven't found one. For example, only 1 out of 5 books on J2EE covered life cycles. College coursework never went into these kinds of details.
Some companies make use of code reviews. To me, this is an excellent way to transfer some of the details between senior and junior developers. Also it serves as a way to point out common pitfalls that junior developers run into. Just having a senior person to ask questions would be something. However, I do not work in such an environment.
Recommendations?
I've gone over the Sun Programmer Certification and again it appears very basic. Are the more advanced certifications helpful?
I've thought about hiring a mentor. Paying him/her to review my code and go over some topics that come up.
Are there any groups available (rather than JUG which just give overviews)?
Any good online resources?
ANY HELP IS APPRECIATIED!!!

Answer 1

Borders isn't going to be very helpful. For cost/demand reasons, brick-and-mortar stores typically favor books with the widest appeal, and you probably won't find many specialized books there. Try borders.com or amazon.com.
Effective Java is a great book for the more experienced programmer, although it's a bit out of date now and it's not J2EE specific.
For J2EE details, download the J2EE spec (on this site somewhere).
For stuff like Struts...you can always download the Struts source code (or the source code of one of its many versions...) and play around with it.
There's plenty of J2EE work out there, and I hate it all. I worked in corporations doing basically J2EE stuff for a long time, and found (1) you seldom need to worry about stuff on the detailed level you're asking about (you just do what you're stuck with), and (2) you spend far less time crafting maintainable, functional, appreciated solutions to real business problems than you do hacking together crap because of awful office politics or deceitful sales staff, and getting blamed later when it doesn't work as advertised (by said deceitful sales staff).