The application is broken in that it does not make submissions idempotent (act
only the first time invoked).  You need to fix the application.

Do not fall into the bottomleess Pit of Despair of trying to "disable the back
button" or otherwise affect browser behavior from the server.

When an application has such a major gaff as failing to handle inputs
correctly, there is little to no long-term help obtained by grafting external
solutions onto the problem.

Consider a servlet filter to guarantee idempotency.  You might use the Token
Pattern in it.

I think your only real solution is to fix the broken application.  You can put
lipstick on a pig but it's still a pig.