its trivial for a script to do a 'wget' to a URL, and the URL can talk to a servlet.
The rest is just a small matter of programming (aka SMOP)
That requires that I:
1. Be awake or have a cron job running.
2. From a second machine.
3. Network functional.
I could, and certainly have given a definite place on my list of possible approaches, have the access protocol to pull the needed data off the server do the active file rotation....
That accomplishes several tasks, all of them well beyond the scope of New to Java forum.
Not the least of those is that I am awake, at the console and can see that the server is up after retirieving the data. It would be a straight one-day study for me to do an MD-5 ( or HMAC or SHA-??? ) and place several of them hardcoded in the servlet. Then I have several approach routes and can drill in to various maintinence tasks without keeping the keys anywhere. ( Okay, passphrase. )
Let's see now;
"Skip Jack the South Pacific Beer Maker.".....
No, how about ......
( beginners, that's a joke for this guy - he will understand )