Retrieve data into Java Application from an HTML file that was launched

So I have been searching for a way to get current location in java (not using any Android APIs) and something that is quite accurate. What I have so far is running an HTML file inside of Java and what I want to do is retrieve the GPS coordinates from a google API (html file).

What I have so far:

HtmlRun.java

import java.awt.Desktop;
import java.io.File;
import java.io.IOException;


public class HtmlRun {

    public static void main(String[] args) throws IOException {
        File htmlFile = new File("findLocation.html");
        Desktop.getDesktop().browse(htmlFile.toURI());

    }

}

findLocation.html

<!DOCTYPE html>
<html>
  <head>
    <title>Geolocation</title>
    <meta name="viewport" content="initial-scale=1.0, user-scalable=no">
    <meta charset="utf-8">
    <style>
      /* Always set the map height explicitly to define the size of the div
       * element that contains the map. */
      #map {
        height: 100%;
      }
      /* Optional: Makes the sample page fill the window. */
      html, body {
        height: 100%;
        margin: 0;
        padding: 0;
      }
    </style>
  </head>
  <body>
    <div id="map"></div>
    <script>
      // Note: This example requires that you consent to location sharing when
      // prompted by your browser. If you see the error "The Geolocation service
      // failed.", it means you probably did not give permission for the browser to
      // locate you.

      function initMap() {
        var map = new google.maps.Map(document.getElementById('map'), {
          center: {lat: -34.397, lng: 150.644},
          zoom: 6
        });
        var infoWindow = new google.maps.InfoWindow({map: map});

        // Try HTML5 geolocation.
        if (navigator.geolocation) {
          navigator.geolocation.getCurrentPosition(function(position) {
            var pos = {
              lat: position.coords.latitude,
              lng: position.coords.longitude
            };

            infoWindow.setPosition(pos);
            infoWindow.setContent('Location found.');
            map.setCenter(pos);
          }, function() {
            handleLocationError(true, infoWindow, map.getCenter());
          });
        } else {
          // Browser doesn't support Geolocation
          handleLocationError(false, infoWindow, map.getCenter());
        }
      }

      function handleLocationError(browserHasGeolocation, infoWindow, pos) {
        infoWindow.setPosition(pos);
        infoWindow.setContent(browserHasGeolocation ?
                              'Error: The Geolocation service failed.' :
                              'Error: Your browser doesn\'t support geolocation.');
      }
    </script>
    <script async defer
    src="https://maps.googleapis.com/maps/api/js?key=AIzaSyBTQzs7iZUtr7v-VbvAWhAql5LiQ9zZrFE&callback=initMap">
    </script>
  </body>
</html>

When I run this, it opens up my default app for html files and everything is sorted... but how could I retrieve the information I need? (GPS coordinates)

It occurs over here:

var pos = {
    lat: position.coords.latitude,
    lng: position.coords.longitude
};

But I don't know how to retrieve that data back into my Java application.

Solution

This here:

public static void main(String[] args) throws IOException {
    File htmlFile = new File("findLocation.html");
    Desktop.getDesktop().browse(htmlFile.toURI());
}

is just opening the html doc in a web browser, after that you have no control AT ALL about what is happening with the web content, the user can even click all the buttons/ pois in the map and you will never get access to that information.

What you need is a webserver that SERVES the content of that app, you can implement REST/full services or even WebSockets to exchange the data between Browser and server