This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
It is not because of framework, html could not cache object such as your list so when you when back, only directly attribute could be kept.
So in this case you have to re-submit this page to get your arraylist agian.