This week's book giveaway is in the OCAJP forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide 1Z0-808 and have Jeanne Boyarsky & Scott Selikoff 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.