title: java create a custom file extension that my application can recognize
body: <p>I want to define a custom file format that my application can recognize. The file will be effectively an archive but I want the file extension to be different and also with a different mimetype. The content of the archive will be in a specific structure so I can easily find the entries. </p>
  
  <p>Also, when a user is uploading, I want the browser to filter the directory and only show only files with this extension.</p>
  
  <p>What is the best approach to address this problem.</p>