Hello hope all is well,
I have been developing code for GPS systems since 2012, and have been in the computer industry since 1979
There are several open source GPS Tracker web applications available free of charge, no usage fees, totally free. They are OpenGTS, and Traccar. OpenGTS is written in completely Java. The server component of Traccar is written in Java, and the UI component is written in JavaScript.
Which one I'd recommend for your application, or as a starting point for further development would depend on your exact requirements.
Please contact me so we can discuss your requirements in detail.