Need suggestions for a Java-based library and service that I can call from my Servlet web app for sending notifications to customers with iOS, Android, Mac, and other such devices/computers.
I am making only a server-based web app. I am not making any iOS, Android, Mac, and any other such app. So I do not have any app on the native OSes to receive and display the notifications.
I need to find a company that provides the Java library for me to call so I can post a notification message to be broadcast to my users. And I need some kind of app provided so the user can receive the notification. Then the user will be notified so they know they need to check in with my web app for further details.