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.
Could be the problem of extracting the parameters from the request. what printStackTrace() is printed? Try to print "e" as it is when e.getMessage() is null. Debug would be the best option to find the exact problem you encountered.
No pain, No gain.
OCJP 1.6, Liferay Certified Developer 6.1