I found this tutorial (Adobe Experience Manager Help | Using Granite DataSource objects to populate AEM Touch UI objects ) and it uses JSP to populate a dropdown list in page properties.
Is it possible to do something similar with Java classes? Perhaps you can link me a tutorial? I've looked around and found nothing.
You can use data source object for populating dropdown using HTL sightly.
Hope this helps!!
This is for getting the property, you can set them as well: Adobe Experience Manager Help | Using an WCMUsePojo class to populate an Experience Manager Touch UI...
Reference post:-Is it possible to access pageProperties from a datasource?