I am wondering, is there a way I can get informations about the device the user is using to navigate the site, perhaps from the request object? Namely, I'd be interested in informations such as the device group to which the user device belongs, and - ideally - informations about the screen size.
I did try adapting the request object to the Device.class, as well as retrieving (successfully so) an instance of the DeviceMapper and then calling the method deviceMapper.getDeviceInstance(request), but I have had zero luck obtaining a non-null instance of the Device class.
In general, I am dubious whether it is even possible to infer informations about the user's device e device's size while working server-side.
I would be very grateful if any of you had any considerations and were willing to illuminate me.
I am not sure why you are getting the device type; if this the only requirement then you can easily get it from User-Agent request header from the request in either sling model or wcmusepojo.like: request.getHeader("User-Agent");
But if your requirement is to use the device size resolution then I would go with viewport from the front-end rather than back-end java. because it will have some impact on your site performance ultimately.