The hardest part will be to find a way to send the SMS messages. This will be just as hard from a website / web application as it is from a desktop application. You either need a connection to a physical phone or telephone system that allows sending SMS, or use a third party that sends SMS messages if you send a request. ASPSMS is one such third party we use at my work. It's not free though, and I don't think you will be able to find a free one - it simply costs money to send SMS messages.
ASPSMS does not have JAR files. They have a full specification that includes how to build an XML request. This request is then sent through HTTP POST to their server, and you receive an XML document back.
I've written a little wrapper around it at my work. Now I can't give you the full code*, but in summary it works like this:
The copying and reading is quite easy; it's little more than using a Reader to read, then copy the chars read to a Writer. Check out classes InputStreamReader and OutputStreamWriter to convert the connection's streams into a Reader/Writer.
The building of the XML string and parsing the result are the hard parts, but even those are not that hard. The XML string can be created using StringBuilder. The parsing can be done using any XML library like JDOM.
1) we are NotACodeMill.
2) the code belongs to my company, not to me. I can't just post it anywhere without approval.