Summary - Want to make a simple website form filler. The website is NOT mine and I cannot edit its source code. Don\'t know what tools/languages are needed. Wou
Sure.
You need a web server and a database on the back end.
Since you feel comfortable with Java, JSP/HTML would probably be an ideal solution.
IMHO...
IMO, If you really just want to fill up some forms to check a reservation, no need to code anything, why not just install a plugin, Selenium, record your actions there and just run it at specified times: http://docs.seleniumhq.org/
I will suggest you try CURL. That will make you solution more simple in my opinion.
You can execute HTTP GET/POST with CURL, which is enough to solve your problem. Give it a try, and if you get block you can ask a more specific question about CURL or HTTP.
Hope it helps.