As a professional electronic shelf labels manufacturer, Sertag can provide flexible solutions for system integrators.so Java or .Net are both ok a Restful API package project, which encapsulate the Cronus project. If your project is using other languages like Java, Python and NodeJS etc., you can use HTTP POST to push data to the Cronus.API. Cross platform support.
Here is the middleware document for you , please check it.
ESL Gen 3.0 Middleware Developer Manual