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.
As Maneesh said, you need to provide us with the proper information in order for us to help you out .
If you are using annotations, it is most likely you are hitting the URL incorrectly or maybe your servlet didnt get registered by the container , can you post your servlet class here ( the one with the name LoginHandler ) . Also I would like you to post your server logs here.