hi sree,

Please don't change your web application to java swing application just for the two reasons you mentioned .Because you can implement both the things (bar code reader and accepting credit cards)easily with in a webapplication.Look at these links.
For barcode task
http://www.barcodelib.com/java_barcode/main.html
For credit card processing task the below link has code to check the authenticity of payment gateway that you are connecting
http://hc.apache.org/httpclient-3.x/authentication.html

regards,
ravindra.