How to validate credit card number which is submitted by the user.
Iam doing a project using servlet.
You could take a look at the merchant connection kit from Cybercash if you are planning to handle the storage of credit cards internal to your system. Cybercash comes with a MCK which handles the connection gateway to the payment gateway server and authorizes the payment ..
See http://mindprod.com/CreditCardValidate.html at Rodey Green's site for examples & source.