Elfinder is a an open-source file manager for web, written in JavaScript using jQuery UI. https://github.com/Studio-42/elFinder
There are some server connector use php, java, C#... The current Java connector is missing implement for Google Drive volume (or I could'n find it on internet).
This implementation integrates Google Dirve as a Cloud volumne to java-connector which is implemented based on java-connector (https://github.com/trustsystems/elfinder-java-connector).
The main customization is in folder: https://github.com/coderhoami4/vstorage-elfinder-java-connector/tree/master/elfinder/elfinder-java-connector-master/src/main/java/br/com/trustsystems/elfinder/core/impl/googledriver
