HTML Audio Element with a fixed source URL where the audio file is recreated on the Apache server after each access by the client

The goal is to detect each time a HTML / Javascript client loads a specific audio file from an Apache Web Server and then replace the file that was just loaded by the client with a new one for the next time the user requests an audio file (reading pages in a story) (e.g. a new file with the same URL as the previous one). Multiple users will be accessing the system and each will get a unique series of audio files created for them based upon their user preferences and the content that they are accessing / studying.

My two questions are:

1. 
   

   How can I get Apache to detect when a specific audio file is accessed by a client and then kick off an action within either an application running on the web server (Java) or on the O/S?

   
   


2. 
   

   What would the best way to name / store the continually recreated audio files such that the files created for each user are kept separate? (I'm considering using the username (which is unique) or using a UUID for the file name...)