A Minecraft plugin that allows admins to easily whitelist multiple players from text files
Run the server with the plugin installed once and a "whitelists/" folder will be created in your plugins folder. Create a text file with a list of usernames you want to easily whitelist or un-whitelist.
After configuring a few lists, run the command /listwhitelist <add/remove> <filename>. This will add or remove all the listed players from your server's whitelist.